caif: Add CAIF HSI Link layer driver

This patch introduces the CAIF HSI Protocol Driver for the
CAIF Link Layer.

This driver implements a platform driver to accommodate for a
platform specific HSI devices. A general platform driver is not
possible as there are no HSI side Kernel API defined.

Signed-off-by: Sjur Brændeland <sjur.brandeland@stericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 1232 insertions, 0 deletions

diff --git a/drivers/net/caif/Kconfig b/drivers/net/caif/Kconfig
index 09ed3f42d673..abf4d7a9dcce 100644
--- a/drivers/net/caif/Kconfig
+++ b/drivers/net/caif/Kconfig
@@ -38,3 +38,12 @@ config CAIF_SHM
 	default n
 	---help---
 	The CAIF shared memory protocol driver for the STE UX5500 platform.
+
+config CAIF_HSI
+       tristate "CAIF HSI transport driver"
+       depends on CAIF
+       default n
+       ---help---
+       The caif low level driver for CAIF over HSI.
+       Be aware that if you enable this then you also need to
+       enable a low-level HSI driver.
diff --git a/drivers/net/caif/Makefile b/drivers/net/caif/Makefile
index 9560b9d624bd..91dff861560f 100644
--- a/drivers/net/caif/Makefile
+++ b/drivers/net/caif/Makefile
@@ -10,3 +10,6 @@ obj-$(CONFIG_CAIF_SPI_SLAVE) += cfspi_slave.o
 # Shared memory
 caif_shm-objs := caif_shmcore.o caif_shm_u5500.o
 obj-$(CONFIG_CAIF_SHM) += caif_shm.o
+
+# HSI interface
+obj-$(CONFIG_CAIF_HSI) += caif_hsi.o
diff --git a/drivers/net/caif/caif_hsi.c b/drivers/net/caif/caif_hsi.c
new file mode 100644
index 000000000000..7a8ce61234a7
--- /dev/null
+++ b/drivers/net/caif/caif_hsi.c
@@ -0,0 +1,1220 @@
+/*
+ * Copyright (C) ST-Ericsson AB 2010
+ * Contact: Sjur Brendeland / sjur.brandeland@stericsson.com
+ * Author:  Daniel Martensson / daniel.martensson@stericsson.com
+ *	    Dmitry.Tarnyagin  / dmitry.tarnyagin@stericsson.com
+ * License terms: GNU General Public License (GPL) version 2.
+ */
+
+#include <linux/version.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/platform_device.h>
+#include <linux/netdevice.h>
+#include <linux/string.h>
+#include <linux/list.h>
+#include <linux/interrupt.h>
+#include <linux/delay.h>
+#include <linux/sched.h>
+#include <linux/if_arp.h>
+#include <linux/timer.h>
+#include <net/caif/caif_layer.h>
+#include <net/caif/caif_hsi.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Daniel Martensson<daniel.martensson@stericsson.com>");
+MODULE_DESCRIPTION("CAIF HSI driver");
+
+/* Returns the number of padding bytes for alignment. */
+#define PAD_POW2(x, pow) ((((x)&((pow)-1)) == 0) ? 0 :\
+				(((pow)-((x)&((pow)-1)))))
+
+/*
+ * HSI padding options.
+ * Warning: must be a base of 2 (& operation used) and can not be zero !
+ */
+static int hsi_head_align = 4;
+module_param(hsi_head_align, int, S_IRUGO);
+MODULE_PARM_DESC(hsi_head_align, "HSI head alignment.");
+
+static int hsi_tail_align = 4;
+module_param(hsi_tail_align, int, S_IRUGO);
+MODULE_PARM_DESC(hsi_tail_align, "HSI tail alignment.");
+
+/*
+ * HSI link layer flowcontrol thresholds.
+ * Warning: A high threshold value migth increase throughput but it will at
+ * the same time prevent channel prioritization and increase the risk of
+ * flooding the modem. The high threshold should be above the low.
+ */
+static int hsi_high_threshold = 100;
+module_param(hsi_high_threshold, int, S_IRUGO);
+MODULE_PARM_DESC(hsi_high_threshold, "HSI high threshold (FLOW OFF).");
+
+static int hsi_low_threshold = 50;
+module_param(hsi_low_threshold, int, S_IRUGO);
+MODULE_PARM_DESC(hsi_low_threshold, "HSI high threshold (FLOW ON).");
+
+#define ON 1
+#define OFF 0
+
+/*
+ * Threshold values for the HSI packet queue. Flowcontrol will be asserted
+ * when the number of packets exceeds HIGH_WATER_MARK. It will not be
+ * de-asserted before the number of packets drops below LOW_WATER_MARK.
+ */
+#define LOW_WATER_MARK   hsi_low_threshold
+#define HIGH_WATER_MARK  hsi_high_threshold
+
+static LIST_HEAD(cfhsi_list);
+static spinlock_t cfhsi_list_lock;
+
+static void cfhsi_inactivity_tout(unsigned long arg)
+{
+	struct cfhsi *cfhsi = (struct cfhsi *)arg;
+
+	dev_dbg(&cfhsi->ndev->dev, "%s.\n",
+		__func__);
+
+	/* Schedule power down work queue. */
+	if (!test_bit(CFHSI_SHUTDOWN, &cfhsi->bits))
+		queue_work(cfhsi->wq, &cfhsi->wake_down_work);
+}
+
+static void cfhsi_abort_tx(struct cfhsi *cfhsi)
+{
+	struct sk_buff *skb;
+
+	for (;;) {
+		spin_lock_bh(&cfhsi->lock);
+		skb = skb_dequeue(&cfhsi->qhead);
+		if (!skb)
+			break;
+
+		cfhsi->ndev->stats.tx_errors++;
+		cfhsi->ndev->stats.tx_dropped++;
+		spin_unlock_bh(&cfhsi->lock);
+		kfree_skb(skb);
+	}
+	cfhsi->tx_state = CFHSI_TX_STATE_IDLE;
+	if (!test_bit(CFHSI_SHUTDOWN, &cfhsi->bits))
+		mod_timer(&cfhsi->timer, jiffies + CFHSI_INACTIVITY_TOUT);
+	spin_unlock_bh(&cfhsi->lock);
+}
+
+static int cfhsi_flush_fifo(struct cfhsi *cfhsi)
+{
+	char buffer[32]; /* Any reasonable value */
+	size_t fifo_occupancy;
+	int ret;
+
+	dev_dbg(&cfhsi->ndev->dev, "%s.\n",
+		__func__);
+
+
+	ret = cfhsi->dev->cfhsi_wake_up(cfhsi->dev);
+	if (ret) {
+		dev_warn(&cfhsi->ndev->dev,
+			"%s: can't wake up HSI interface: %d.\n",
+			__func__, ret);
+		return ret;
+	}
+
+	do {
+		ret = cfhsi->dev->cfhsi_fifo_occupancy(cfhsi->dev,
+				&fifo_occupancy);
+		if (ret) {
+			dev_warn(&cfhsi->ndev->dev,
+				"%s: can't get FIFO occupancy: %d.\n",
+				__func__, ret);
+			break;
+		} else if (!fifo_occupancy)
+			/* No more data, exitting normally */
+			break;
+
+		fifo_occupancy = min(sizeof(buffer), fifo_occupancy);
+		set_bit(CFHSI_FLUSH_FIFO, &cfhsi->bits);
+		ret = cfhsi->dev->cfhsi_rx(buffer, fifo_occupancy,
+				cfhsi->dev);
+		if (ret) {
+			clear_bit(CFHSI_FLUSH_FIFO, &cfhsi->bits);
+			dev_warn(&cfhsi->ndev->dev,
+				"%s: can't read data: %d.\n",
+				__func__, ret);
+			break;
+		}
+
+		ret = 5 * HZ;
+		wait_event_interruptible_timeout(cfhsi->flush_fifo_wait,
+			 !test_bit(CFHSI_FLUSH_FIFO, &cfhsi->bits), ret);
+
+		if (ret < 0) {
+			dev_warn(&cfhsi->ndev->dev,
+				"%s: can't wait for flush complete: %d.\n",
+				__func__, ret);
+			break;
+		} else if (!ret) {
+			ret = -ETIMEDOUT;
+			dev_warn(&cfhsi->ndev->dev,
+				"%s: timeout waiting for flush complete.\n",
+				__func__);
+			break;
+		}
+	} while (1);
+
+	cfhsi->dev->cfhsi_wake_down(cfhsi->dev);
+
+	return ret;
+}
+
+static int cfhsi_tx_frm(struct cfhsi_desc *desc, struct cfhsi *cfhsi)
+{
+	int nfrms = 0;
+	int pld_len = 0;
+	struct sk_buff *skb;
+	u8 *pfrm = desc->emb_frm + CFHSI_MAX_EMB_FRM_SZ;
+
+	skb = skb_dequeue(&cfhsi->qhead);
+	if (!skb)
+		return 0;
+
+	/* Check if we can embed a CAIF frame. */
+	if (skb->len < CFHSI_MAX_EMB_FRM_SZ) {
+		struct caif_payload_info *info;
+		int hpad = 0;
+		int tpad = 0;
+
+		/* Calculate needed head alignment and tail alignment. */
+		info = (struct caif_payload_info *)&skb->cb;
+
+		hpad = 1 + PAD_POW2((info->hdr_len + 1), hsi_head_align);
+		tpad = PAD_POW2((skb->len + hpad), hsi_tail_align);
+
+		/* Check if frame still fits with added alignment. */
+		if ((skb->len + hpad + tpad) <= CFHSI_MAX_EMB_FRM_SZ) {
+			u8 *pemb = desc->emb_frm;
+			desc->offset = CFHSI_DESC_SHORT_SZ;
+			*pemb = (u8)(hpad - 1);
+			pemb += hpad;
+
+			/* Update network statistics. */
+			cfhsi->ndev->stats.tx_packets++;
+			cfhsi->ndev->stats.tx_bytes += skb->len;
+
+			/* Copy in embedded CAIF frame. */
+			skb_copy_bits(skb, 0, pemb, skb->len);
+			consume_skb(skb);
+			skb = NULL;
+		}
+	} else
+		/* Clear offset. */
+		desc->offset = 0;
+
+	/* Create payload CAIF frames. */
+	pfrm = desc->emb_frm + CFHSI_MAX_EMB_FRM_SZ;
+	while (nfrms < CFHSI_MAX_PKTS) {
+		struct caif_payload_info *info;
+		int hpad = 0;
+		int tpad = 0;
+
+		if (!skb)
+			skb = skb_dequeue(&cfhsi->qhead);
+
+		if (!skb)
+			break;
+
+		/* Calculate needed head alignment and tail alignment. */
+		info = (struct caif_payload_info *)&skb->cb;
+
+		hpad = 1 + PAD_POW2((info->hdr_len + 1), hsi_head_align);
+		tpad = PAD_POW2((skb->len + hpad), hsi_tail_align);
+
+		/* Fill in CAIF frame length in descriptor. */
+		desc->cffrm_len[nfrms] = hpad + skb->len + tpad;
+
+		/* Fill head padding information. */
+		*pfrm = (u8)(hpad - 1);
+		pfrm += hpad;
+
+		/* Update network statistics. */
+		cfhsi->ndev->stats.tx_packets++;
+		cfhsi->ndev->stats.tx_bytes += skb->len;
+
+		/* Copy in CAIF frame. */
+		skb_copy_bits(skb, 0, pfrm, skb->len);
+
+		/* Update payload length. */
+		pld_len += desc->cffrm_len[nfrms];
+
+		/* Update frame pointer. */
+		pfrm += skb->len + tpad;
+		consume_skb(skb);
+		skb = NULL;
+
+		/* Update number of frames. */
+		nfrms++;
+	}
+
+	/* Unused length fields should be zero-filled (according to SPEC). */
+	while (nfrms < CFHSI_MAX_PKTS) {
+		desc->cffrm_len[nfrms] = 0x0000;
+		nfrms++;
+	}
+
+	/* Check if we can piggy-back another descriptor. */
+	skb = skb_peek(&cfhsi->qhead);
+	if (skb)
+		desc->header |= CFHSI_PIGGY_DESC;
+	else
+		desc->header &= ~CFHSI_PIGGY_DESC;
+
+	return CFHSI_DESC_SZ + pld_len;
+}
+
+static void cfhsi_tx_done_work(struct work_struct *work)
+{
+	struct cfhsi *cfhsi = NULL;
+	struct cfhsi_desc *desc = NULL;
+	int len = 0;
+	int res;
+
+	cfhsi = container_of(work, struct cfhsi, tx_done_work);
+	dev_dbg(&cfhsi->ndev->dev, "%s.\n",
+		__func__);
+
+	if (test_bit(CFHSI_SHUTDOWN, &cfhsi->bits))
+		return;
+
+	desc = (struct cfhsi_desc *)cfhsi->tx_buf;
+
+	do {
+		/*
+		 * Send flow on if flow off has been previously signalled
+		 * and number of packets is below low water mark.
+		 */
+		spin_lock_bh(&cfhsi->lock);
+		if (cfhsi->flow_off_sent &&
+				cfhsi->qhead.qlen <= cfhsi->q_low_mark &&
+				cfhsi->cfdev.flowctrl) {
+
+			cfhsi->flow_off_sent = 0;
+			cfhsi->cfdev.flowctrl(cfhsi->ndev, ON);
+		}
+		spin_unlock_bh(&cfhsi->lock);
+
+		/* Create HSI frame. */
+		len = cfhsi_tx_frm(desc, cfhsi);
+		if (!len) {
+			cfhsi->tx_state = CFHSI_TX_STATE_IDLE;
+			/* Start inactivity timer. */
+			mod_timer(&cfhsi->timer,
+					jiffies + CFHSI_INACTIVITY_TOUT);
+			break;
+		}
+
+		/* Set up new transfer. */
+		res = cfhsi->dev->cfhsi_tx(cfhsi->tx_buf, len, cfhsi->dev);
+		if (WARN_ON(res < 0)) {
+			dev_err(&cfhsi->ndev->dev, "%s: TX error %d.\n",
+				__func__, res);
+		}
+	} while (res < 0);
+}
+
+static void cfhsi_tx_done_cb(struct cfhsi_drv *drv)
+{
+	struct cfhsi *cfhsi;
+
+	cfhsi = container_of(drv, struct cfhsi, drv);
+	dev_dbg(&cfhsi->ndev->dev, "%s.\n",
+		__func__);
+
+	if (test_bit(CFHSI_SHUTDOWN, &cfhsi->bits))
+		return;
+
+	queue_work(cfhsi->wq, &cfhsi->tx_done_work);
+}
+
+static int cfhsi_rx_desc(struct cfhsi_desc *desc, struct cfhsi *cfhsi)
+{
+	int xfer_sz = 0;
+	int nfrms = 0;
+	u16 *plen = NULL;
+	u8 *pfrm = NULL;
+
+	if ((desc->header & ~CFHSI_PIGGY_DESC) ||
+			(desc->offset > CFHSI_MAX_EMB_FRM_SZ)) {
+		dev_err(&cfhsi->ndev->dev, "%s: Invalid descriptor.\n",
+			__func__);
+		return 0;
+	}
+
+	/* Check for embedded CAIF frame. */
+	if (desc->offset) {
+		struct sk_buff *skb;
+		u8 *dst = NULL;
+		int len = 0, retries = 0;
+		pfrm = ((u8 *)desc) + desc->offset;
+
+		/* Remove offset padding. */
+		pfrm += *pfrm + 1;
+
+		/* Read length of CAIF frame (little endian). */
+		len = *pfrm;
+		len |= ((*(pfrm+1)) << 8) & 0xFF00;
+		len += 2;	/* Add FCS fields. */
+
+
+		/* Allocate SKB (OK even in IRQ context). */
+		skb = alloc_skb(len + 1, GFP_KERNEL);
+		while (!skb) {
+			retries++;
+			schedule_timeout(1);
+			skb = alloc_skb(len + 1, GFP_KERNEL);
+			if (skb) {
+				printk(KERN_WARNING "%s: slept for %u "
+						"before getting memory\n",
+						__func__, retries);
+				break;
+			}
+			if (retries > HZ) {
+				printk(KERN_ERR "%s: slept for 1HZ and "
+						"did not get memory\n",
+						__func__);
+				cfhsi->ndev->stats.rx_dropped++;
+				goto drop_frame;
+			}
+		}
+		caif_assert(skb != NULL);
+
+		dst = skb_put(skb, len);
+		memcpy(dst, pfrm, len);
+
+		skb->protocol = htons(ETH_P_CAIF);
+		skb_reset_mac_header(skb);
+		skb->dev = cfhsi->ndev;
+
+		/*
+		 * We are called from a arch specific platform device.
+		 * Unfortunately we don't know what context we're
+		 * running in.
+		 */
+		if (in_interrupt())
+			netif_rx(skb);
+		else
+			netif_rx_ni(skb);
+
+		/* Update network statistics. */
+		cfhsi->ndev->stats.rx_packets++;
+		cfhsi->ndev->stats.rx_bytes += len;
+	}
+
+drop_frame:
+	/* Calculate transfer length. */
+	plen = desc->cffrm_len;
+	while (nfrms < CFHSI_MAX_PKTS && *plen) {
+		xfer_sz += *plen;
+		plen++;
+		nfrms++;
+	}
+
+	/* Check for piggy-backed descriptor. */
+	if (desc->header & CFHSI_PIGGY_DESC)
+		xfer_sz += CFHSI_DESC_SZ;
+
+	if (xfer_sz % 4) {
+		dev_err(&cfhsi->ndev->dev,
+				"%s: Invalid payload len: %d, ignored.\n",
+			__func__, xfer_sz);
+		xfer_sz = 0;
+	}
+
+	return xfer_sz;
+}
+
+static int cfhsi_rx_pld(struct cfhsi_desc *desc, struct cfhsi *cfhsi)
+{
+	int rx_sz = 0;
+	int nfrms = 0;
+	u16 *plen = NULL;
+	u8 *pfrm = NULL;
+
+	/* Sanity check header and offset. */
+	if (WARN_ON((desc->header & ~CFHSI_PIGGY_DESC) ||
+			(desc->offset > CFHSI_MAX_EMB_FRM_SZ))) {
+		dev_err(&cfhsi->ndev->dev, "%s: Invalid descriptor.\n",
+			__func__);
+		return -EINVAL;
+	}
+
+	/* Set frame pointer to start of payload. */
+	pfrm = desc->emb_frm + CFHSI_MAX_EMB_FRM_SZ;
+	plen = desc->cffrm_len;
+	while (nfrms < CFHSI_MAX_PKTS && *plen) {
+		struct sk_buff *skb;
+		u8 *dst = NULL;
+		u8 *pcffrm = NULL;
+		int len = 0, retries = 0;
+
+		if (WARN_ON(desc->cffrm_len[nfrms] > CFHSI_MAX_PAYLOAD_SZ)) {
+			dev_err(&cfhsi->ndev->dev, "%s: Invalid payload.\n",
+				__func__);
+			return -EINVAL;
+		}
+
+		/* CAIF frame starts after head padding. */
+		pcffrm = pfrm + *pfrm + 1;
+
+		/* Read length of CAIF frame (little endian). */
+		len = *pcffrm;
+		len |= ((*(pcffrm + 1)) << 8) & 0xFF00;
+		len += 2;	/* Add FCS fields. */
+
+		/* Allocate SKB (OK even in IRQ context). */
+		skb = alloc_skb(len + 1, GFP_KERNEL);
+		while (!skb) {
+			retries++;
+			schedule_timeout(1);
+			skb = alloc_skb(len + 1, GFP_KERNEL);
+			if (skb) {
+				printk(KERN_WARNING "%s: slept for %u "
+						"before getting memory\n",
+						__func__, retries);
+				break;
+			}
+			if (retries > HZ) {
+				printk(KERN_ERR "%s: slept for 1HZ "
+						"and did not get memory\n",
+						__func__);
+				cfhsi->ndev->stats.rx_dropped++;
+				goto drop_frame;
+			}
+		}
+		caif_assert(skb != NULL);
+
+		dst = skb_put(skb, len);
+		memcpy(dst, pcffrm, len);
+
+		skb->protocol = htons(ETH_P_CAIF);
+		skb_reset_mac_header(skb);
+		skb->dev = cfhsi->ndev;
+
+		/*
+		 * We're called from a platform device,
+		 * and don't know the context we're running in.
+		 */
+		if (in_interrupt())
+			netif_rx(skb);
+		else
+			netif_rx_ni(skb);
+
+		/* Update network statistics. */
+		cfhsi->ndev->stats.rx_packets++;
+		cfhsi->ndev->stats.rx_bytes += len;
+
+drop_frame:
+		pfrm += *plen;
+		rx_sz += *plen;
+		plen++;
+		nfrms++;
+	}
+
+	return rx_sz;
+}
+
+static void cfhsi_rx_done_work(struct work_struct *work)
+{
+	int res;
+	int desc_pld_len = 0;
+	struct cfhsi *cfhsi = NULL;
+	struct cfhsi_desc *desc = NULL;
+
+	cfhsi = container_of(work, struct cfhsi, rx_done_work);
+	desc = (struct cfhsi_desc *)cfhsi->rx_buf;
+
+	dev_dbg(&cfhsi->ndev->dev, "%s: Kick timer if pending.\n",
+		__func__);
+
+	if (test_bit(CFHSI_SHUTDOWN, &cfhsi->bits))
+		return;
+
+	/* Update inactivity timer if pending. */
+	mod_timer_pending(&cfhsi->timer, jiffies + CFHSI_INACTIVITY_TOUT);
+
+	if (cfhsi->rx_state == CFHSI_RX_STATE_DESC) {
+		desc_pld_len = cfhsi_rx_desc(desc, cfhsi);
+	} else {
+		int pld_len;
+
+		pld_len = cfhsi_rx_pld(desc, cfhsi);
+
+		if ((pld_len > 0) && (desc->header & CFHSI_PIGGY_DESC)) {
+			struct cfhsi_desc *piggy_desc;
+			piggy_desc = (struct cfhsi_desc *)
+				(desc->emb_frm + CFHSI_MAX_EMB_FRM_SZ +
+						pld_len);
+
+			/* Extract piggy-backed descriptor. */
+			desc_pld_len = cfhsi_rx_desc(piggy_desc, cfhsi);
+
+			/*
+			 * Copy needed information from the piggy-backed
+			 * descriptor to the descriptor in the start.
+			 */
+			memcpy((u8 *)desc, (u8 *)piggy_desc,
+					CFHSI_DESC_SHORT_SZ);
+		}
+	}
+
+	if (desc_pld_len) {
+		cfhsi->rx_state = CFHSI_RX_STATE_PAYLOAD;
+		cfhsi->rx_ptr = cfhsi->rx_buf + CFHSI_DESC_SZ;
+		cfhsi->rx_len = desc_pld_len;
+	} else {
+		cfhsi->rx_state = CFHSI_RX_STATE_DESC;
+		cfhsi->rx_ptr = cfhsi->rx_buf;
+		cfhsi->rx_len = CFHSI_DESC_SZ;
+	}
+	clear_bit(CFHSI_PENDING_RX, &cfhsi->bits);
+
+	if (test_bit(CFHSI_AWAKE, &cfhsi->bits)) {
+		/* Set up new transfer. */
+		dev_dbg(&cfhsi->ndev->dev, "%s: Start RX.\n",
+			__func__);
+		res = cfhsi->dev->cfhsi_rx(cfhsi->rx_ptr, cfhsi->rx_len,
+				cfhsi->dev);
+		if (WARN_ON(res < 0)) {
+			dev_err(&cfhsi->ndev->dev, "%s: RX error %d.\n",
+				__func__, res);
+			cfhsi->ndev->stats.rx_errors++;
+			cfhsi->ndev->stats.rx_dropped++;
+		}
+	}
+}
+
+static void cfhsi_rx_done_cb(struct cfhsi_drv *drv)
+{
+	struct cfhsi *cfhsi;
+
+	cfhsi = container_of(drv, struct cfhsi, drv);
+	dev_dbg(&cfhsi->ndev->dev, "%s.\n",
+		__func__);
+
+	if (test_bit(CFHSI_SHUTDOWN, &cfhsi->bits))
+		return;
+
+	set_bit(CFHSI_PENDING_RX, &cfhsi->bits);
+
+	if (test_and_clear_bit(CFHSI_FLUSH_FIFO, &cfhsi->bits))
+		wake_up_interruptible(&cfhsi->flush_fifo_wait);
+	else
+		queue_work(cfhsi->wq, &cfhsi->rx_done_work);
+}
+
+static void cfhsi_wake_up(struct work_struct *work)
+{
+	struct cfhsi *cfhsi = NULL;
+	int res;
+	int len;
+	long ret;
+
+	cfhsi = container_of(work, struct cfhsi, wake_up_work);
+
+	if (test_bit(CFHSI_SHUTDOWN, &cfhsi->bits))
+		return;
+
+	if (unlikely(test_bit(CFHSI_AWAKE, &cfhsi->bits))) {
+		/* It happenes when wakeup is requested by
+		 * both ends at the same time. */
+		clear_bit(CFHSI_WAKE_UP, &cfhsi->bits);
+		return;
+	}
+
+	/* Activate wake line. */
+	cfhsi->dev->cfhsi_wake_up(cfhsi->dev);
+
+	dev_dbg(&cfhsi->ndev->dev, "%s: Start waiting.\n",
+		__func__);
+
+	/* Wait for acknowledge. */
+	ret = CFHSI_WAKEUP_TOUT;
+	wait_event_interruptible_timeout(cfhsi->wake_up_wait,
+					test_bit(CFHSI_WAKE_UP_ACK,
+							&cfhsi->bits), ret);
+	if (unlikely(ret < 0)) {
+		/* Interrupted by signal. */
+		dev_info(&cfhsi->ndev->dev, "%s: Signalled: %ld.\n",
+			__func__, ret);
+		clear_bit(CFHSI_WAKE_UP, &cfhsi->bits);
+		cfhsi->dev->cfhsi_wake_down(cfhsi->dev);
+		return;
+	} else if (!ret) {
+		/* Wakeup timeout */
+		dev_err(&cfhsi->ndev->dev, "%s: Timeout.\n",
+			__func__);
+		clear_bit(CFHSI_WAKE_UP, &cfhsi->bits);
+		cfhsi->dev->cfhsi_wake_down(cfhsi->dev);
+		return;
+	}
+	dev_dbg(&cfhsi->ndev->dev, "%s: Woken.\n",
+		__func__);
+
+	/* Clear power up bit. */
+	set_bit(CFHSI_AWAKE, &cfhsi->bits);
+	clear_bit(CFHSI_WAKE_UP, &cfhsi->bits);
+
+	/* Resume read operation. */
+	if (!test_bit(CFHSI_PENDING_RX, &cfhsi->bits)) {
+		dev_dbg(&cfhsi->ndev->dev, "%s: Start RX.\n",
+			__func__);
+		res = cfhsi->dev->cfhsi_rx(cfhsi->rx_ptr,
+				cfhsi->rx_len, cfhsi->dev);
+		if (WARN_ON(res < 0)) {
+			dev_err(&cfhsi->ndev->dev, "%s: RX error %d.\n",
+				__func__, res);
+		}
+	}
+
+	/* Clear power up acknowledment. */
+	clear_bit(CFHSI_WAKE_UP_ACK, &cfhsi->bits);
+
+	spin_lock_bh(&cfhsi->lock);
+
+	/* Resume transmit if queue is not empty. */
+	if (!skb_peek(&cfhsi->qhead)) {
+		dev_dbg(&cfhsi->ndev->dev, "%s: Peer wake, start timer.\n",
+			__func__);
+		/* Start inactivity timer. */
+		mod_timer(&cfhsi->timer,
+				jiffies + CFHSI_INACTIVITY_TOUT);
+		spin_unlock_bh(&cfhsi->lock);
+		return;
+	}
+
+	dev_dbg(&cfhsi->ndev->dev, "%s: Host wake.\n",
+		__func__);
+
+	spin_unlock_bh(&cfhsi->lock);
+
+	/* Create HSI frame. */
+	len = cfhsi_tx_frm((struct cfhsi_desc *)cfhsi->tx_buf, cfhsi);
+
+	if (likely(len > 0)) {
+		/* Set up new transfer. */
+		res = cfhsi->dev->cfhsi_tx(cfhsi->tx_buf, len, cfhsi->dev);
+		if (WARN_ON(res < 0)) {
+			dev_err(&cfhsi->ndev->dev, "%s: TX error %d.\n",
+				__func__, res);
+			cfhsi_abort_tx(cfhsi);
+		}
+	} else {
+		dev_err(&cfhsi->ndev->dev,
+				"%s: Failed to create HSI frame: %d.\n",
+				__func__, len);
+	}
+
+}
+
+static void cfhsi_wake_down(struct work_struct *work)
+{
+	long ret;
+	struct cfhsi *cfhsi = NULL;
+	size_t fifo_occupancy;
+
+	cfhsi = container_of(work, struct cfhsi, wake_down_work);
+	dev_dbg(&cfhsi->ndev->dev, "%s.\n",
+		__func__);
+
+	if (test_bit(CFHSI_SHUTDOWN, &cfhsi->bits))
+		return;
+
+	/* Check if there is something in FIFO. */
+	if (WARN_ON(cfhsi->dev->cfhsi_fifo_occupancy(cfhsi->dev,
+							&fifo_occupancy)))
+		fifo_occupancy = 0;
+
+	if (fifo_occupancy) {
+		dev_dbg(&cfhsi->ndev->dev,
+				"%s: %u words in RX FIFO, restart timer.\n",
+				__func__, (unsigned) fifo_occupancy);
+		spin_lock_bh(&cfhsi->lock);
+		mod_timer(&cfhsi->timer,
+				jiffies + CFHSI_INACTIVITY_TOUT);
+		spin_unlock_bh(&cfhsi->lock);
+		return;
+	}
+
+	/* Cancel pending RX requests */
+	cfhsi->dev->cfhsi_rx_cancel(cfhsi->dev);
+
+	/* Deactivate wake line. */
+	cfhsi->dev->cfhsi_wake_down(cfhsi->dev);
+
+	/* Wait for acknowledge. */
+	ret = CFHSI_WAKEUP_TOUT;
+	ret = wait_event_interruptible_timeout(cfhsi->wake_down_wait,
+					test_bit(CFHSI_WAKE_DOWN_ACK,
+							&cfhsi->bits),
+					ret);
+	if (ret < 0) {
+		/* Interrupted by signal. */
+		dev_info(&cfhsi->ndev->dev, "%s: Signalled: %ld.\n",
+			__func__, ret);
+		return;
+	} else if (!ret) {
+		/* Timeout */
+		dev_err(&cfhsi->ndev->dev, "%s: Timeout.\n",
+			__func__);
+	}
+
+	/* Clear power down acknowledment. */
+	clear_bit(CFHSI_WAKE_DOWN_ACK, &cfhsi->bits);
+	clear_bit(CFHSI_AWAKE, &cfhsi->bits);
+
+	/* Check if there is something in FIFO. */
+	if (WARN_ON(cfhsi->dev->cfhsi_fifo_occupancy(cfhsi->dev,
+							&fifo_occupancy)))
+		fifo_occupancy = 0;
+
+	if (fifo_occupancy) {
+		dev_dbg(&cfhsi->ndev->dev,
+				"%s: %u words in RX FIFO, wakeup forced.\n",
+				__func__, (unsigned) fifo_occupancy);
+		if (!test_and_set_bit(CFHSI_WAKE_UP, &cfhsi->bits))
+			queue_work(cfhsi->wq, &cfhsi->wake_up_work);
+	} else
+		dev_dbg(&cfhsi->ndev->dev, "%s: Done.\n",
+			__func__);
+}
+
+static void cfhsi_wake_up_cb(struct cfhsi_drv *drv)
+{
+	struct cfhsi *cfhsi = NULL;
+
+	cfhsi = container_of(drv, struct cfhsi, drv);
+	dev_dbg(&cfhsi->ndev->dev, "%s.\n",
+		__func__);
+
+	set_bit(CFHSI_WAKE_UP_ACK, &cfhsi->bits);
+	wake_up_interruptible(&cfhsi->wake_up_wait);
+
+	if (test_bit(CFHSI_SHUTDOWN, &cfhsi->bits))
+		return;
+
+	/* Schedule wake up work queue if the peer initiates. */
+	if (!test_and_set_bit(CFHSI_WAKE_UP, &cfhsi->bits))
+		queue_work(cfhsi->wq, &cfhsi->wake_up_work);
+}
+
+static void cfhsi_wake_down_cb(struct cfhsi_drv *drv)
+{
+	struct cfhsi *cfhsi = NULL;
+
+	cfhsi = container_of(drv, struct cfhsi, drv);
+	dev_dbg(&cfhsi->ndev->dev, "%s.\n",
+		__func__);
+
+	/* Initiating low power is only permitted by the host (us). */
+	set_bit(CFHSI_WAKE_DOWN_ACK, &cfhsi->bits);
+	wake_up_interruptible(&cfhsi->wake_down_wait);
+}
+
+static int cfhsi_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	struct cfhsi *cfhsi = NULL;
+	int start_xfer = 0;
+	int timer_active;
+
+	if (!dev)
+		return -EINVAL;
+
+	cfhsi = netdev_priv(dev);
+
+	spin_lock_bh(&cfhsi->lock);
+
+	skb_queue_tail(&cfhsi->qhead, skb);
+
+	/* Sanity check; xmit should not be called after unregister_netdev */
+	if (WARN_ON(test_bit(CFHSI_SHUTDOWN, &cfhsi->bits))) {
+		spin_unlock_bh(&cfhsi->lock);
+		cfhsi_abort_tx(cfhsi);
+		return -EINVAL;
+	}
+
+	/* Send flow off if number of packets is above high water mark. */
+	if (!cfhsi->flow_off_sent &&
+		cfhsi->qhead.qlen > cfhsi->q_high_mark &&
+		cfhsi->cfdev.flowctrl) {
+		cfhsi->flow_off_sent = 1;
+		cfhsi->cfdev.flowctrl(cfhsi->ndev, OFF);
+	}
+
+	if (cfhsi->tx_state == CFHSI_TX_STATE_IDLE) {
+		cfhsi->tx_state = CFHSI_TX_STATE_XFER;
+		start_xfer = 1;
+	}
+
+	spin_unlock_bh(&cfhsi->lock);
+
+	if (!start_xfer)
+		return 0;
+
+	/* Delete inactivity timer if started. */
+#ifdef CONFIG_SMP
+	timer_active = del_timer_sync(&cfhsi->timer);
+#else
+	timer_active = del_timer(&cfhsi->timer);
+#endif /* CONFIG_SMP */
+
+	if (timer_active) {
+		struct cfhsi_desc *desc = (struct cfhsi_desc *)cfhsi->tx_buf;
+		int len;
+		int res;
+
+		/* Create HSI frame. */
+		len = cfhsi_tx_frm(desc, cfhsi);
+		BUG_ON(!len);
+
+		/* Set up new transfer. */
+		res = cfhsi->dev->cfhsi_tx(cfhsi->tx_buf, len, cfhsi->dev);
+		if (WARN_ON(res < 0)) {
+			dev_err(&cfhsi->ndev->dev, "%s: TX error %d.\n",
+				__func__, res);
+			cfhsi_abort_tx(cfhsi);
+		}
+	} else {
+		/* Schedule wake up work queue if the we initiate. */
+		if (!test_and_set_bit(CFHSI_WAKE_UP, &cfhsi->bits))
+			queue_work(cfhsi->wq, &cfhsi->wake_up_work);
+	}
+
+	return 0;
+}
+
+static int cfhsi_open(struct net_device *dev)
+{
+	netif_wake_queue(dev);
+
+	return 0;
+}
+
+static int cfhsi_close(struct net_device *dev)
+{
+	netif_stop_queue(dev);
+
+	return 0;
+}
+
+static const struct net_device_ops cfhsi_ops = {
+	.ndo_open = cfhsi_open,
+	.ndo_stop = cfhsi_close,
+	.ndo_start_xmit = cfhsi_xmit
+};
+
+static void cfhsi_setup(struct net_device *dev)
+{
+	struct cfhsi *cfhsi = netdev_priv(dev);
+	dev->features = 0;
+	dev->netdev_ops = &cfhsi_ops;
+	dev->type = ARPHRD_CAIF;
+	dev->flags = IFF_POINTOPOINT | IFF_NOARP;
+	dev->mtu = CFHSI_MAX_PAYLOAD_SZ;
+	dev->tx_queue_len = 0;
+	dev->destructor = free_netdev;
+	skb_queue_head_init(&cfhsi->qhead);
+	cfhsi->cfdev.link_select = CAIF_LINK_HIGH_BANDW;
+	cfhsi->cfdev.use_frag = false;
+	cfhsi->cfdev.use_stx = false;
+	cfhsi->cfdev.use_fcs = false;
+	cfhsi->ndev = dev;
+}
+
+int cfhsi_probe(struct platform_device *pdev)
+{
+	struct cfhsi *cfhsi = NULL;
+	struct net_device *ndev;
+	struct cfhsi_dev *dev;
+	int res;
+
+	ndev = alloc_netdev(sizeof(struct cfhsi), "cfhsi%d", cfhsi_setup);
+	if (!ndev) {
+		dev_err(&pdev->dev, "%s: alloc_netdev failed.\n",
+			__func__);
+		return -ENODEV;
+	}
+
+	cfhsi = netdev_priv(ndev);
+	cfhsi->ndev = ndev;
+	cfhsi->pdev = pdev;
+
+	/* Initialize state vaiables. */
+	cfhsi->tx_state = CFHSI_TX_STATE_IDLE;
+	cfhsi->rx_state = CFHSI_RX_STATE_DESC;
+
+	/* Set flow info */
+	cfhsi->flow_off_sent = 0;
+	cfhsi->q_low_mark = LOW_WATER_MARK;
+	cfhsi->q_high_mark = HIGH_WATER_MARK;
+
+	/* Assign the HSI device. */
+	dev = (struct cfhsi_dev *)pdev->dev.platform_data;
+	cfhsi->dev = dev;
+
+	/* Assign the driver to this HSI device. */
+	dev->drv = &cfhsi->drv;
+
+	/*
+	 * Allocate a TX buffer with the size of a HSI packet descriptors
+	 * and the necessary room for CAIF payload frames.
+	 */
+	cfhsi->tx_buf = kzalloc(CFHSI_BUF_SZ_TX, GFP_KERNEL);
+	if (!cfhsi->tx_buf) {
+		dev_err(&ndev->dev, "%s: Failed to allocate TX buffer.\n",
+			__func__);
+		res = -ENODEV;
+		goto err_alloc_tx;
+	}
+
+	/*
+	 * Allocate a RX buffer with the size of two HSI packet descriptors and
+	 * the necessary room for CAIF payload frames.
+	 */
+	cfhsi->rx_buf = kzalloc(CFHSI_BUF_SZ_RX, GFP_KERNEL);
+	if (!cfhsi->rx_buf) {
+		dev_err(&ndev->dev, "%s: Failed to allocate RX buffer.\n",
+			__func__);
+		res = -ENODEV;
+		goto err_alloc_rx;
+	}
+
+	/* Initialize recieve vaiables. */
+	cfhsi->rx_ptr = cfhsi->rx_buf;
+	cfhsi->rx_len = CFHSI_DESC_SZ;
+
+	/* Initialize spin locks. */
+	spin_lock_init(&cfhsi->lock);
+
+	/* Set up the driver. */
+	cfhsi->drv.tx_done_cb = cfhsi_tx_done_cb;
+	cfhsi->drv.rx_done_cb = cfhsi_rx_done_cb;
+
+	/* Initialize the work queues. */
+	INIT_WORK(&cfhsi->wake_up_work, cfhsi_wake_up);
+	INIT_WORK(&cfhsi->wake_down_work, cfhsi_wake_down);
+	INIT_WORK(&cfhsi->rx_done_work, cfhsi_rx_done_work);
+	INIT_WORK(&cfhsi->tx_done_work, cfhsi_tx_done_work);
+
+	/* Clear all bit fields. */
+	clear_bit(CFHSI_WAKE_UP_ACK, &cfhsi->bits);
+	clear_bit(CFHSI_WAKE_DOWN_ACK, &cfhsi->bits);
+	clear_bit(CFHSI_WAKE_UP, &cfhsi->bits);
+	clear_bit(CFHSI_AWAKE, &cfhsi->bits);
+	clear_bit(CFHSI_PENDING_RX, &cfhsi->bits);
+
+	/* Create work thread. */
+	cfhsi->wq = create_singlethread_workqueue(pdev->name);
+	if (!cfhsi->wq) {
+		dev_err(&ndev->dev, "%s: Failed to create work queue.\n",
+			__func__);
+		res = -ENODEV;
+		goto err_create_wq;
+	}
+
+	/* Initialize wait queues. */
+	init_waitqueue_head(&cfhsi->wake_up_wait);
+	init_waitqueue_head(&cfhsi->wake_down_wait);
+	init_waitqueue_head(&cfhsi->flush_fifo_wait);
+
+	/* Setup the inactivity timer. */
+	init_timer(&cfhsi->timer);
+	cfhsi->timer.data = (unsigned long)cfhsi;
+	cfhsi->timer.function = cfhsi_inactivity_tout;
+
+	/* Add CAIF HSI device to list. */
+	spin_lock(&cfhsi_list_lock);
+	list_add_tail(&cfhsi->list, &cfhsi_list);
+	spin_unlock(&cfhsi_list_lock);
+
+	/* Activate HSI interface. */
+	res = cfhsi->dev->cfhsi_up(cfhsi->dev);
+	if (res) {
+		dev_err(&cfhsi->ndev->dev,
+			"%s: can't activate HSI interface: %d.\n",
+			__func__, res);
+		goto err_activate;
+	}
+
+	/* Flush FIFO */
+	res = cfhsi_flush_fifo(cfhsi);
+	if (res) {
+		dev_err(&ndev->dev, "%s: Can't flush FIFO: %d.\n",
+			__func__, res);
+		goto err_net_reg;
+	}
+
+	cfhsi->drv.wake_up_cb = cfhsi_wake_up_cb;
+	cfhsi->drv.wake_down_cb = cfhsi_wake_down_cb;
+
+	/* Register network device. */
+	res = register_netdev(ndev);
+	if (res) {
+		dev_err(&ndev->dev, "%s: Registration error: %d.\n",
+			__func__, res);
+		goto err_net_reg;
+	}
+
+	netif_stop_queue(ndev);
+
+	return res;
+
+ err_net_reg:
+	cfhsi->dev->cfhsi_down(cfhsi->dev);
+ err_activate:
+	destroy_workqueue(cfhsi->wq);
+ err_create_wq:
+	kfree(cfhsi->rx_buf);
+ err_alloc_rx:
+	kfree(cfhsi->tx_buf);
+ err_alloc_tx:
+	free_netdev(ndev);
+
+	return res;
+}
+
+static void cfhsi_shutdown(struct cfhsi *cfhsi, bool remove_platform_dev)
+{
+	u8 *tx_buf, *rx_buf;
+
+	/* Stop TXing */
+	netif_tx_stop_all_queues(cfhsi->ndev);
+
+	/* going to shutdown driver */
+	set_bit(CFHSI_SHUTDOWN, &cfhsi->bits);
+
+	if (remove_platform_dev) {
+		/* Flush workqueue */
+		flush_workqueue(cfhsi->wq);
+
+		/* Notify device. */
+		platform_device_unregister(cfhsi->pdev);
+	}
+
+	/* Flush workqueue */
+	flush_workqueue(cfhsi->wq);
+
+	/* Delete timer if pending */
+#ifdef CONFIG_SMP
+	del_timer_sync(&cfhsi->timer);
+#else
+	del_timer(&cfhsi->timer);
+#endif /* CONFIG_SMP */
+
+	/* Cancel pending RX request (if any) */
+	cfhsi->dev->cfhsi_rx_cancel(cfhsi->dev);
+
+	/* Flush again and destroy workqueue */
+	destroy_workqueue(cfhsi->wq);
+
+	/* Store bufferes: will be freed later. */
+	tx_buf = cfhsi->tx_buf;
+	rx_buf = cfhsi->rx_buf;
+
+	/* Flush transmit queues. */
+	cfhsi_abort_tx(cfhsi);
+
+	/* Deactivate interface */
+	cfhsi->dev->cfhsi_down(cfhsi->dev);
+
+	/* Finally unregister the network device. */
+	unregister_netdev(cfhsi->ndev);
+
+	/* Free buffers. */
+	kfree(tx_buf);
+	kfree(rx_buf);
+}
+
+int cfhsi_remove(struct platform_device *pdev)
+{
+	struct list_head *list_node;
+	struct list_head *n;
+	struct cfhsi *cfhsi = NULL;
+	struct cfhsi_dev *dev;
+
+	dev = (struct cfhsi_dev *)pdev->dev.platform_data;
+	spin_lock(&cfhsi_list_lock);
+	list_for_each_safe(list_node, n, &cfhsi_list) {
+		cfhsi = list_entry(list_node, struct cfhsi, list);
+		/* Find the corresponding device. */
+		if (cfhsi->dev == dev) {
+			/* Remove from list. */
+			list_del(list_node);
+			spin_unlock(&cfhsi_list_lock);
+
+			/* Shutdown driver. */
+			cfhsi_shutdown(cfhsi, false);
+
+			return 0;
+		}
+	}
+	spin_unlock(&cfhsi_list_lock);
+	return -ENODEV;
+}
+
+struct platform_driver cfhsi_plat_drv = {
+	.probe = cfhsi_probe,
+	.remove = cfhsi_remove,
+	.driver = {
+		   .name = "cfhsi",
+		   .owner = THIS_MODULE,
+		   },
+};
+
+static void __exit cfhsi_exit_module(void)
+{
+	struct list_head *list_node;
+	struct list_head *n;
+	struct cfhsi *cfhsi = NULL;
+
+	spin_lock(&cfhsi_list_lock);
+	list_for_each_safe(list_node, n, &cfhsi_list) {
+		cfhsi = list_entry(list_node, struct cfhsi, list);
+
+		/* Remove from list. */
+		list_del(list_node);
+		spin_unlock(&cfhsi_list_lock);
+
+		/* Shutdown driver. */
+		cfhsi_shutdown(cfhsi, true);
+
+		spin_lock(&cfhsi_list_lock);
+	}
+	spin_unlock(&cfhsi_list_lock);
+
+	/* Unregister platform driver. */
+	platform_driver_unregister(&cfhsi_plat_drv);
+}
+
+static int __init cfhsi_init_module(void)
+{
+	int result;
+
+	/* Initialize spin lock. */
+	spin_lock_init(&cfhsi_list_lock);
+
+	/* Register platform driver. */
+	result = platform_driver_register(&cfhsi_plat_drv);
+	if (result) {
+		printk(KERN_ERR "Could not register platform HSI driver: %d.\n",
+			result);
+		goto err_dev_register;
+	}
+
+	return result;
+
+ err_dev_register:
+	return result;
+}
+
+module_init(cfhsi_init_module);
+module_exit(cfhsi_exit_module);