b43: Add PIO support for PCMCIA devices

This adds PIO support back (D'oh!) for PCMCIA devices.
This is a complete rewrite of the old PIO code. It does actually work
and we get reasonable performance out of it on a modern machine.
On a PowerBook G4 I get a few MBit for TX and a few more for RX.
So it doesn't work as well as DMA (of course), but it's a _lot_ faster
than the old PIO code (only got a few kBit with that).

The limiting factor is the host CPU speed. So it will generate 100%
CPU usage when the network interface is heavily loaded. A voluntary preemption
point in the RX path makes sure Desktop Latency isn't hurt.

PIO is needed for 16bit PCMCIA devices, as we really don't want to poke with
the braindead DMA mechanisms on PCMCIA sockets. Additionally, not all
PCMCIA sockets do actually support DMA in 16bit mode (mine doesn't).

Signed-off-by: Michael Buesch <mb@bu3sch.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 64 insertions, 56 deletions

diff --git a/drivers/net/wireless/b43/dma.c b/drivers/net/wireless/b43/dma.c
index 70db0570adc5..f1b983cb9c1f 100644
--- a/drivers/net/wireless/b43/dma.c
+++ b/drivers/net/wireless/b43/dma.c
@@ -550,7 +550,6 @@ static int setup_rx_descbuffer(struct b43_dmaring *ring,
 			       struct b43_dmadesc_meta *meta, gfp_t gfp_flags)
 {
 	struct b43_rxhdr_fw4 *rxhdr;
-	struct b43_hwtxstatus *txstat;
 	dma_addr_t dmaaddr;
 	struct sk_buff *skb;
 
@@ -586,8 +585,6 @@ static int setup_rx_descbuffer(struct b43_dmaring *ring,
 
 	rxhdr = (struct b43_rxhdr_fw4 *)(skb->data);
 	rxhdr->frame_len = 0;
-	txstat = (struct b43_hwtxstatus *)(skb->data);
-	txstat->cookie = 0;
 
 	return 0;
 }
@@ -776,6 +773,18 @@ static u64 supported_dma_mask(struct b43_wldev *dev)
 	return DMA_30BIT_MASK;
 }
 
+static enum b43_dmatype dma_mask_to_engine_type(u64 dmamask)
+{
+	if (dmamask == DMA_30BIT_MASK)
+		return B43_DMA_30BIT;
+	if (dmamask == DMA_32BIT_MASK)
+		return B43_DMA_32BIT;
+	if (dmamask == DMA_64BIT_MASK)
+		return B43_DMA_64BIT;
+	B43_WARN_ON(1);
+	return B43_DMA_30BIT;
+}
+
 /* Main initialization function. */
 static
 struct b43_dmaring *b43_setup_dmaring(struct b43_wldev *dev,
@@ -956,7 +965,11 @@ static void b43_destroy_dmaring(struct b43_dmaring *ring,
 
 void b43_dma_free(struct b43_wldev *dev)
 {
-	struct b43_dma *dma = &dev->dma;
+	struct b43_dma *dma;
+
+	if (b43_using_pio_transfers(dev))
+		return;
+	dma = &dev->dma;
 
 	destroy_ring(dma, rx_ring);
 	destroy_ring(dma, tx_ring_AC_BK);
@@ -974,19 +987,7 @@ int b43_dma_init(struct b43_wldev *dev)
 	enum b43_dmatype type;
 
 	dmamask = supported_dma_mask(dev);
-	switch (dmamask) {
-	default:
-		B43_WARN_ON(1);
-	case DMA_30BIT_MASK:
-		type = B43_DMA_30BIT;
-		break;
-	case DMA_32BIT_MASK:
-		type = B43_DMA_32BIT;
-		break;
-	case DMA_64BIT_MASK:
-		type = B43_DMA_64BIT;
-		break;
-	}
+	type = dma_mask_to_engine_type(dmamask);
 	err = ssb_dma_set_mask(dev->dev, dmamask);
 	if (err) {
 		b43err(dev->wl, "The machine/kernel does not support "
@@ -1113,7 +1114,6 @@ static int dma_tx_fragment(struct b43_dmaring *ring,
 	size_t hdrsize = b43_txhdr_size(ring->dev);
 
 #define SLOTS_PER_PACKET  2
-	B43_WARN_ON(skb_shinfo(skb)->nr_frags);
 
 	old_top_slot = ring->current_slot;
 	old_used_slots = ring->used_slots;
@@ -1257,11 +1257,6 @@ int b43_dma_tx(struct b43_wldev *dev,
 	int err = 0;
 	unsigned long flags;
 
-	if (unlikely(skb->len < 2 + 2 + 6)) {
-		/* Too short, this can't be a valid frame. */
-		return -EINVAL;
-	}
-
 	hdr = (struct ieee80211_hdr *)skb->data;
 	if (ctl->flags & IEEE80211_TXCTL_SEND_AFTER_DTIM) {
 		/* The multicast ring will be sent after the DTIM */
@@ -1319,38 +1314,6 @@ out_unlock:
 	return err;
 }
 
-static void b43_fill_txstatus_report(struct b43_dmaring *ring,
-				    struct ieee80211_tx_status *report,
-				    const struct b43_txstatus *status)
-{
-	bool frame_failed = 0;
-
-	if (status->acked) {
-		/* The frame was ACKed. */
-		report->flags |= IEEE80211_TX_STATUS_ACK;
-	} else {
-		/* The frame was not ACKed... */
-		if (!(report->control.flags & IEEE80211_TXCTL_NO_ACK)) {
-			/* ...but we expected an ACK. */
-			frame_failed = 1;
-			report->excessive_retries = 1;
-		}
-	}
-	if (status->frame_count == 0) {
-		/* The frame was not transmitted at all. */
-		report->retry_count = 0;
-	} else {
-		report->retry_count = status->frame_count - 1;
-#ifdef CONFIG_B43_DEBUG
-		if (frame_failed)
-			ring->nr_failed_tx_packets++;
-		else
-			ring->nr_succeed_tx_packets++;
-		ring->nr_total_packet_tries += status->frame_count;
-#endif /* DEBUG */
-	}
-}
-
 /* Called with IRQs disabled. */
 void b43_dma_handle_txstatus(struct b43_wldev *dev,
 			     const struct b43_txstatus *status)
@@ -1360,6 +1323,7 @@ void b43_dma_handle_txstatus(struct b43_wldev *dev,
 	struct b43_dmadesc_generic *desc;
 	struct b43_dmadesc_meta *meta;
 	int slot;
+	bool frame_succeed;
 
 	ring = parse_cookie(dev, status->cookie, &slot);
 	if (unlikely(!ring))
@@ -1386,7 +1350,15 @@ void b43_dma_handle_txstatus(struct b43_wldev *dev,
 			 * status of the transmission.
 			 * Some fields of txstat are already filled in dma_tx().
 			 */
-			b43_fill_txstatus_report(ring, &(meta->txstat), status);
+			frame_succeed = b43_fill_txstatus_report(
+						&(meta->txstat), status);
+#ifdef CONFIG_B43_DEBUG
+			if (frame_succeed)
+				ring->nr_succeed_tx_packets++;
+			else
+				ring->nr_failed_tx_packets++;
+			ring->nr_total_packet_tries += status->frame_count;
+#endif /* DEBUG */
 			ieee80211_tx_status_irqsafe(dev->wl->hw, meta->skb,
 						    &(meta->txstat));
 			/* skb is freed by ieee80211_tx_status_irqsafe() */
@@ -1573,3 +1545,39 @@ void b43_dma_tx_resume(struct b43_wldev *dev)
 	b43_dma_tx_resume_ring(dev->dma.tx_ring_AC_BK);
 	b43_power_saving_ctl_bits(dev, 0);
 }
+
+#ifdef CONFIG_B43_PIO
+static void direct_fifo_rx(struct b43_wldev *dev, enum b43_dmatype type,
+			   u16 mmio_base, bool enable)
+{
+	u32 ctl;
+
+	if (type == B43_DMA_64BIT) {
+		ctl = b43_read32(dev, mmio_base + B43_DMA64_RXCTL);
+		ctl &= ~B43_DMA64_RXDIRECTFIFO;
+		if (enable)
+			ctl |= B43_DMA64_RXDIRECTFIFO;
+		b43_write32(dev, mmio_base + B43_DMA64_RXCTL, ctl);
+	} else {
+		ctl = b43_read32(dev, mmio_base + B43_DMA32_RXCTL);
+		ctl &= ~B43_DMA32_RXDIRECTFIFO;
+		if (enable)
+			ctl |= B43_DMA32_RXDIRECTFIFO;
+		b43_write32(dev, mmio_base + B43_DMA32_RXCTL, ctl);
+	}
+}
+
+/* Enable/Disable Direct FIFO Receive Mode (PIO) on a RX engine.
+ * This is called from PIO code, so DMA structures are not available. */
+void b43_dma_direct_fifo_rx(struct b43_wldev *dev,
+			    unsigned int engine_index, bool enable)
+{
+	enum b43_dmatype type;
+	u16 mmio_base;
+
+	type = dma_mask_to_engine_type(supported_dma_mask(dev));
+
+	mmio_base = b43_dmacontroller_base(type, engine_index);
+	direct_fifo_rx(dev, type, mmio_base, enable);
+}
+#endif /* CONFIG_B43_PIO */