spi: create a message queueing infrastructure

This rips the message queue in the PL022 driver out and pushes
it into (optional) common infrastructure. Drivers that want to
use the message pumping thread will need to define the new
per-messags transfer methods and leave the deprecated transfer()
method as NULL.

Most of the design is described in the documentation changes that
are included in this patch.

Since there is a queue that need to be stopped when the system
is suspending/resuming, two new calls are implemented for the
device drivers to call in their suspend()/resume() functions:
spi_master_suspend() and spi_master_resume().

ChangeLog v1->v2:
- Remove Kconfig entry and do not make the queue support optional
  at all, instead be more agressive and have it as part of the
  compulsory infrastructure.
- If the .transfer() method is implemented, delete print a small
  deprecation notice and do not start the transfer pump.
- Fix a bitrotted comment.
ChangeLog v2->v3:
- Fix up a problematic sequence courtesy of Chris Blair.
- Stop rather than destroy the queue on suspend() courtesy of
  Chris Blair.

Signed-off-by: Chris Blair <chris.blair@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

1 files changed, 52 insertions, 251 deletions

diff --git a/drivers/spi/spi-pl022.c b/drivers/spi/spi-pl022.c
index 81847c9a7586..ec17a7af7e28 100644
--- a/drivers/spi/spi-pl022.c
+++ b/drivers/spi/spi-pl022.c
@@ -29,7 +29,6 @@
 #include <linux/errno.h>
 #include <linux/interrupt.h>
 #include <linux/spi/spi.h>
-#include <linux/kthread.h>
 #include <linux/delay.h>
 #include <linux/clk.h>
 #include <linux/err.h>
@@ -41,7 +40,6 @@
 #include <linux/dma-mapping.h>
 #include <linux/scatterlist.h>
 #include <linux/pm_runtime.h>
-#include <linux/sched.h>
 
 /*
  * This macro is used to define some register default values.
@@ -367,15 +365,7 @@ struct pl022 {
 	struct clk			*clk;
 	struct spi_master		*master;
 	struct pl022_ssp_controller	*master_info;
-	/* Driver message pump */
-	struct kthread_worker		kworker;
-	struct task_struct		*kworker_task;
-	struct kthread_work		pump_messages;
-	spinlock_t			queue_lock;
-	struct list_head		queue;
-	bool				busy;
-	bool				running;
-	/* Message transfer pump */
+	/* Message per-transfer pump */
 	struct tasklet_struct		pump_transfers;
 	struct spi_message		*cur_msg;
 	struct spi_transfer		*cur_transfer;
@@ -397,6 +387,7 @@ struct pl022 {
 	struct sg_table			sgt_rx;
 	struct sg_table			sgt_tx;
 	char				*dummypage;
+	bool				dma_running;
 #endif
 };
 
@@ -451,8 +442,6 @@ static void null_cs_control(u32 command)
 static void giveback(struct pl022 *pl022)
 {
 	struct spi_transfer *last_transfer;
-	unsigned long flags;
-	struct spi_message *msg;
 	pl022->next_msg_cs_active = false;
 
 	last_transfer = list_entry(pl022->cur_msg->transfers.prev,
@@ -480,15 +469,8 @@ static void giveback(struct pl022 *pl022)
 		 * sent the current message could be unloaded, which
 		 * could invalidate the cs_control() callback...
 		 */
-
 		/* get a pointer to the next message, if any */
-		spin_lock_irqsave(&pl022->queue_lock, flags);
-		if (list_empty(&pl022->queue))
-			next_msg = NULL;
-		else
-			next_msg = list_entry(pl022->queue.next,
-					struct spi_message, queue);
-		spin_unlock_irqrestore(&pl022->queue_lock, flags);
+		next_msg = spi_get_next_queued_message(pl022->master);
 
 		/*
 		 * see if the next and current messages point
@@ -500,19 +482,13 @@ static void giveback(struct pl022 *pl022)
 			pl022->cur_chip->cs_control(SSP_CHIP_DESELECT);
 		else
 			pl022->next_msg_cs_active = true;
+
 	}
 
-	spin_lock_irqsave(&pl022->queue_lock, flags);
-	msg = pl022->cur_msg;
 	pl022->cur_msg = NULL;
 	pl022->cur_transfer = NULL;
 	pl022->cur_chip = NULL;
-	queue_kthread_work(&pl022->kworker, &pl022->pump_messages);
-	spin_unlock_irqrestore(&pl022->queue_lock, flags);
-
-	msg->state = NULL;
-	if (msg->complete)
-		msg->complete(msg->context);
+	spi_finalize_current_message(pl022->master);
 }
 
 /**
@@ -1066,6 +1042,7 @@ static int configure_dma(struct pl022 *pl022)
 	dmaengine_submit(txdesc);
 	dma_async_issue_pending(rxchan);
 	dma_async_issue_pending(txchan);
+	pl022->dma_running = true;
 
 	return 0;
 
@@ -1144,11 +1121,12 @@ static void terminate_dma(struct pl022 *pl022)
 	dmaengine_terminate_all(rxchan);
 	dmaengine_terminate_all(txchan);
 	unmap_free_dma_scatter(pl022);
+	pl022->dma_running = false;
 }
 
 static void pl022_dma_remove(struct pl022 *pl022)
 {
-	if (pl022->busy)
+	if (pl022->dma_running)
 		terminate_dma(pl022);
 	if (pl022->dma_tx_channel)
 		dma_release_channel(pl022->dma_tx_channel);
@@ -1496,73 +1474,20 @@ out:
 	return;
 }
 
-/**
- * pump_messages - kthread work function which processes spi message queue
- * @work: pointer to kthread work struct contained in the pl022 private struct
- *
- * This function checks if there is any spi message in the queue that
- * needs processing and delegate control to appropriate function
- * do_polling_transfer()/do_interrupt_dma_transfer()
- * based on the kind of the transfer
- *
- */
-static void pump_messages(struct kthread_work *work)
+static int pl022_transfer_one_message(struct spi_master *master,
+				      struct spi_message *msg)
 {
-	struct pl022 *pl022 =
-		container_of(work, struct pl022, pump_messages);
-	unsigned long flags;
-	bool was_busy = false;
-
-	/* Lock queue and check for queue work */
-	spin_lock_irqsave(&pl022->queue_lock, flags);
-	if (list_empty(&pl022->queue) || !pl022->running) {
-		if (pl022->busy) {
-			/* nothing more to do - disable spi/ssp and power off */
-			writew((readw(SSP_CR1(pl022->virtbase)) &
-				(~SSP_CR1_MASK_SSE)), SSP_CR1(pl022->virtbase));
-
-			if (pl022->master_info->autosuspend_delay > 0) {
-				pm_runtime_mark_last_busy(&pl022->adev->dev);
-				pm_runtime_put_autosuspend(&pl022->adev->dev);
-			} else {
-				pm_runtime_put(&pl022->adev->dev);
-			}
-		}
-		pl022->busy = false;
-		spin_unlock_irqrestore(&pl022->queue_lock, flags);
-		return;
-	}
-
-	/* Make sure we are not already running a message */
-	if (pl022->cur_msg) {
-		spin_unlock_irqrestore(&pl022->queue_lock, flags);
-		return;
-	}
-	/* Extract head of queue */
-	pl022->cur_msg =
-	    list_entry(pl022->queue.next, struct spi_message, queue);
-
-	list_del_init(&pl022->cur_msg->queue);
-	if (pl022->busy)
-		was_busy = true;
-	else
-		pl022->busy = true;
-	spin_unlock_irqrestore(&pl022->queue_lock, flags);
+	struct pl022 *pl022 = spi_master_get_devdata(master);
 
 	/* Initial message state */
-	pl022->cur_msg->state = STATE_START;
-	pl022->cur_transfer = list_entry(pl022->cur_msg->transfers.next,
-					    struct spi_transfer, transfer_list);
+	pl022->cur_msg = msg;
+	msg->state = STATE_START;
+
+	pl022->cur_transfer = list_entry(msg->transfers.next,
+					 struct spi_transfer, transfer_list);
 
 	/* Setup the SPI using the per chip configuration */
-	pl022->cur_chip = spi_get_ctldata(pl022->cur_msg->spi);
-	if (!was_busy)
-		/*
-		 * We enable the core voltage and clocks here, then the clocks
-		 * and core will be disabled when this thread is run again
-		 * and there is no more work to be done.
-		 */
-		pm_runtime_get_sync(&pl022->adev->dev);
+	pl022->cur_chip = spi_get_ctldata(msg->spi);
 
 	restore_state(pl022);
 	flush(pl022);
@@ -1571,119 +1496,37 @@ static void pump_messages(struct kthread_work *work)
 		do_polling_transfer(pl022);
 	else
 		do_interrupt_dma_transfer(pl022);
-}
-
-static int __init init_queue(struct pl022 *pl022)
-{
-	struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
-
-	INIT_LIST_HEAD(&pl022->queue);
-	spin_lock_init(&pl022->queue_lock);
-
-	pl022->running = false;
-	pl022->busy = false;
-
-	tasklet_init(&pl022->pump_transfers, pump_transfers,
-			(unsigned long)pl022);
-
-	init_kthread_worker(&pl022->kworker);
-	pl022->kworker_task = kthread_run(kthread_worker_fn,
-					&pl022->kworker,
-					dev_name(pl022->master->dev.parent));
-	if (IS_ERR(pl022->kworker_task)) {
-		dev_err(&pl022->adev->dev,
-			"failed to create message pump task\n");
-		return -ENOMEM;
-	}
-	init_kthread_work(&pl022->pump_messages, pump_messages);
-
-	/*
-	 * Board config will indicate if this controller should run the
-	 * message pump with high (realtime) priority to reduce the transfer
-	 * latency on the bus by minimising the delay between a transfer
-	 * request and the scheduling of the message pump thread. Without this
-	 * setting the message pump thread will remain at default priority.
-	 */
-	if (pl022->master_info->rt) {
-		dev_info(&pl022->adev->dev,
-			"will run message pump with realtime priority\n");
-		sched_setscheduler(pl022->kworker_task, SCHED_FIFO, &param);
-	}
 
 	return 0;
 }
 
-static int start_queue(struct pl022 *pl022)
+static int pl022_prepare_transfer_hardware(struct spi_master *master)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&pl022->queue_lock, flags);
-
-	if (pl022->running || pl022->busy) {
-		spin_unlock_irqrestore(&pl022->queue_lock, flags);
-		return -EBUSY;
-	}
-
-	pl022->running = true;
-	pl022->cur_msg = NULL;
-	pl022->cur_transfer = NULL;
-	pl022->cur_chip = NULL;
-	pl022->next_msg_cs_active = false;
-	spin_unlock_irqrestore(&pl022->queue_lock, flags);
-
-	queue_kthread_work(&pl022->kworker, &pl022->pump_messages);
+	struct pl022 *pl022 = spi_master_get_devdata(master);
 
+	/*
+	 * Just make sure we have all we need to run the transfer by syncing
+	 * with the runtime PM framework.
+	 */
+	pm_runtime_get_sync(&pl022->adev->dev);
 	return 0;
 }
 
-static int stop_queue(struct pl022 *pl022)
+static int pl022_unprepare_transfer_hardware(struct spi_master *master)
 {
-	unsigned long flags;
-	unsigned limit = 500;
-	int status = 0;
+	struct pl022 *pl022 = spi_master_get_devdata(master);
 
-	spin_lock_irqsave(&pl022->queue_lock, flags);
+	/* nothing more to do - disable spi/ssp and power off */
+	writew((readw(SSP_CR1(pl022->virtbase)) &
+		(~SSP_CR1_MASK_SSE)), SSP_CR1(pl022->virtbase));
 
-	/* This is a bit lame, but is optimized for the common execution path.
-	 * A wait_queue on the pl022->busy could be used, but then the common
-	 * execution path (pump_messages) would be required to call wake_up or
-	 * friends on every SPI message. Do this instead */
-	while ((!list_empty(&pl022->queue) || pl022->busy) && limit--) {
-		spin_unlock_irqrestore(&pl022->queue_lock, flags);
-		msleep(10);
-		spin_lock_irqsave(&pl022->queue_lock, flags);
+	if (pl022->master_info->autosuspend_delay > 0) {
+		pm_runtime_mark_last_busy(&pl022->adev->dev);
+		pm_runtime_put_autosuspend(&pl022->adev->dev);
+	} else {
+		pm_runtime_put(&pl022->adev->dev);
 	}
 
-	if (!list_empty(&pl022->queue) || pl022->busy)
-		status = -EBUSY;
-	else
-		pl022->running = false;
-
-	spin_unlock_irqrestore(&pl022->queue_lock, flags);
-
-	return status;
-}
-
-static int destroy_queue(struct pl022 *pl022)
-{
-	int status;
-
-	status = stop_queue(pl022);
-
-	/*
-	 * We are unloading the module or failing to load (only two calls
-	 * to this routine), and neither call can handle a return value.
-	 * However, flush_kthread_worker will block until all work is done.
-	 * If the reason that stop_queue timed out is that the work will never
-	 * finish, then it does no good to call flush/stop thread, so
-	 * return anyway.
-	 */
-	if (status != 0)
-		return status;
-
-	flush_kthread_worker(&pl022->kworker);
-	kthread_stop(pl022->kworker_task);
-
 	return 0;
 }
 
@@ -1803,38 +1646,6 @@ static int verify_controller_parameters(struct pl022 *pl022,
 	return 0;
 }
 
-/**
- * pl022_transfer - transfer function registered to SPI master framework
- * @spi: spi device which is requesting transfer
- * @msg: spi message which is to handled is queued to driver queue
- *
- * This function is registered to the SPI framework for this SPI master
- * controller. It will queue the spi_message in the queue of driver if
- * the queue is not stopped and return.
- */
-static int pl022_transfer(struct spi_device *spi, struct spi_message *msg)
-{
-	struct pl022 *pl022 = spi_master_get_devdata(spi->master);
-	unsigned long flags;
-
-	spin_lock_irqsave(&pl022->queue_lock, flags);
-
-	if (!pl022->running) {
-		spin_unlock_irqrestore(&pl022->queue_lock, flags);
-		return -ESHUTDOWN;
-	}
-	msg->actual_length = 0;
-	msg->status = -EINPROGRESS;
-	msg->state = STATE_START;
-
-	list_add_tail(&msg->queue, &pl022->queue);
-	if (pl022->running && !pl022->busy)
-		queue_kthread_work(&pl022->kworker, &pl022->pump_messages);
-
-	spin_unlock_irqrestore(&pl022->queue_lock, flags);
-	return 0;
-}
-
 static inline u32 spi_rate(u32 rate, u16 cpsdvsr, u16 scr)
 {
 	return rate / (cpsdvsr * (1 + scr));
@@ -2197,7 +2008,10 @@ pl022_probe(struct amba_device *adev, const struct amba_id *id)
 	master->num_chipselect = platform_info->num_chipselect;
 	master->cleanup = pl022_cleanup;
 	master->setup = pl022_setup;
-	master->transfer = pl022_transfer;
+	master->prepare_transfer_hardware = pl022_prepare_transfer_hardware;
+	master->transfer_one_message = pl022_transfer_one_message;
+	master->unprepare_transfer_hardware = pl022_unprepare_transfer_hardware;
+	master->rt = platform_info->rt;
 
 	/*
 	 * Supports mode 0-3, loopback, and active low CS. Transfers are
@@ -2241,6 +2055,10 @@ pl022_probe(struct amba_device *adev, const struct amba_id *id)
 		goto err_no_clk_en;
 	}
 
+	/* Initialize transfer pump */
+	tasklet_init(&pl022->pump_transfers, pump_transfers,
+		     (unsigned long)pl022);
+
 	/* Disable SSP */
 	writew((readw(SSP_CR1(pl022->virtbase)) & (~SSP_CR1_MASK_SSE)),
 	       SSP_CR1(pl022->virtbase));
@@ -2260,17 +2078,6 @@ pl022_probe(struct amba_device *adev, const struct amba_id *id)
 			platform_info->enable_dma = 0;
 	}
 
-	/* Initialize and start queue */
-	status = init_queue(pl022);
-	if (status != 0) {
-		dev_err(&adev->dev, "probe - problem initializing queue\n");
-		goto err_init_queue;
-	}
-	status = start_queue(pl022);
-	if (status != 0) {
-		dev_err(&adev->dev, "probe - problem starting queue\n");
-		goto err_start_queue;
-	}
 	/* Register with the SPI framework */
 	amba_set_drvdata(adev, pl022);
 	status = spi_register_master(master);
@@ -2296,9 +2103,6 @@ pl022_probe(struct amba_device *adev, const struct amba_id *id)
 	return 0;
 
  err_spi_register:
- err_start_queue:
- err_init_queue:
-	destroy_queue(pl022);
 	if (platform_info->enable_dma)
 		pl022_dma_remove(pl022);
 
@@ -2334,9 +2138,6 @@ pl022_remove(struct amba_device *adev)
 	 */
 	pm_runtime_get_noresume(&adev->dev);
 
-	/* Remove the queue */
-	if (destroy_queue(pl022) != 0)
-		dev_err(&adev->dev, "queue remove failed\n");
 	load_ssp_default_config(pl022);
 	if (pl022->master_info->enable_dma)
 		pl022_dma_remove(pl022);
@@ -2358,12 +2159,12 @@ pl022_remove(struct amba_device *adev)
 static int pl022_suspend(struct device *dev)
 {
 	struct pl022 *pl022 = dev_get_drvdata(dev);
-	int status = 0;
+	int ret;
 
-	status = stop_queue(pl022);
-	if (status) {
-		dev_warn(dev, "suspend cannot stop queue\n");
-		return status;
+	ret = spi_master_suspend(pl022->master);
+	if (ret) {
+		dev_warn(dev, "cannot suspend master\n");
+		return ret;
 	}
 
 	dev_dbg(dev, "suspended\n");
@@ -2373,16 +2174,16 @@ static int pl022_suspend(struct device *dev)
 static int pl022_resume(struct device *dev)
 {
 	struct pl022 *pl022 = dev_get_drvdata(dev);
-	int status = 0;
+	int ret;
 
 	/* Start the queue running */
-	status = start_queue(pl022);
-	if (status)
-		dev_err(dev, "problem starting queue (%d)\n", status);
+	ret = spi_master_resume(pl022->master);
+	if (ret)
+		dev_err(dev, "problem starting queue (%d)\n", ret);
 	else
 		dev_dbg(dev, "resumed\n");
 
-	return status;
+	return ret;
 }
 #endif	/* CONFIG_PM */