dmaengine: pxa_dma: implement device_synchronize

Implement the function which wait until a dma channel is stopped to have
a synchronization point.

This also protects the pxad_remove() from races, such as spurious
interrupts while removing the driver, because :
 - as long as there is one dma channel requested, ie. dma_chan_get() but
   no dma_chan_put(), the try_module_get() of dma_chan_get() prevents
   the remove() routine from running
 - when the last channel is released, ie. the last dma_chan_put() is
   called, if there is a running DMA, pxad_synchronize() is called
 - pxad_synchronize() waits for the channel to stop, which in turn
   ensures on pxa architecture that the interrupt cannot be fired anymore

Reported-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

diff --git a/drivers/dma/pxa_dma.c b/drivers/dma/pxa_dma.c
index 1966c526fdbcb65cf681deb900a6e5668d58d625..dc7850a422b8d4212495d067c4ea31c26e0af8a2 100644 (file)
--- a/drivers/dma/pxa_dma.c
+++ b/drivers/dma/pxa_dma.c
@@ -21,6 +21,7 @@
 #include <linux/of_device.h>
 #include <linux/of_dma.h>
 #include <linux/of.h>
+#include <linux/wait.h>
 #include <linux/dma/pxa-dma.h>
 
 #include "dmaengine.h"
@@ -118,6 +119,8 @@ struct pxad_chan {
        struct pxad_phy         *phy;
        struct dma_pool         *desc_pool;     /* Descriptors pool */
        dma_cookie_t            bus_error;
+
+       wait_queue_head_t       wq_state;
 };
 
 struct pxad_device {
@@ -571,6 +574,7 @@ static void pxad_launch_chan(struct pxad_chan *chan,
         */
        phy_writel(chan->phy, desc->first, DDADR);
        phy_enable(chan->phy, chan->misaligned);
+       wake_up(&chan->wq_state);
 }
 
 static void set_updater_desc(struct pxad_desc_sw *sw_desc,
@@ -716,6 +720,7 @@ static irqreturn_t pxad_chan_handler(int irq, void *dev_id)
                }
        }
        spin_unlock_irqrestore(&chan->vc.lock, flags);
+       wake_up(&chan->wq_state);
 
        return IRQ_HANDLED;
 }
@@ -1267,6 +1272,14 @@ static enum dma_status pxad_tx_status(struct dma_chan *dchan,
        return ret;
 }
 
+static void pxad_synchronize(struct dma_chan *dchan)
+{
+       struct pxad_chan *chan = to_pxad_chan(dchan);
+
+       wait_event(chan->wq_state, !is_chan_running(chan));
+       vchan_synchronize(&chan->vc);
+}
+
 static void pxad_free_channels(struct dma_device *dmadev)
 {
        struct pxad_chan *c, *cn;
@@ -1371,6 +1384,7 @@ static int pxad_init_dmadev(struct platform_device *op,
        pdev->slave.device_tx_status = pxad_tx_status;
        pdev->slave.device_issue_pending = pxad_issue_pending;
        pdev->slave.device_config = pxad_config;
+       pdev->slave.device_synchronize = pxad_synchronize;
        pdev->slave.device_terminate_all = pxad_terminate_all;
 
        if (op->dev.coherent_dma_mask)
@@ -1388,6 +1402,7 @@ static int pxad_init_dmadev(struct platform_device *op,
                        return -ENOMEM;
                c->vc.desc_free = pxad_free_desc;
                vchan_init(&c->vc, &pdev->slave);
+               init_waitqueue_head(&c->wq_state);
        }
 
        return dma_async_device_register(&pdev->slave);