[media] saa7164: use an MSI interrupt when available

Enhances driver to use an MSI interrupt when available.

Adds the module option 'enable_msi' (type bool) which by default is
enabled. Can be set to 'N' to disable.

Fixes (or can reduce the occurrence of) a crash which is most commonly
reported when both digital tuners of the saa7164 chip is in use. A
reported example can be found here:
http://permalink.gmane.org/gmane.linux.drivers.video-input-infrastructure/83948

Reviewed-by: Steven Toth <stoth@kernellabs.com>
Signed-off-by: Brendan McGrath <redmcg@redmandi.dyndns.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

diff --git a/drivers/media/pci/saa7164/saa7164-core.c b/drivers/media/pci/saa7164/saa7164-core.c
index 90de807..3206a82 100644 (file)
--- a/drivers/media/pci/saa7164/saa7164-core.c
+++ b/drivers/media/pci/saa7164/saa7164-core.c
@@ -85,6 +85,11 @@ module_param(guard_checking, int, 0644);
 MODULE_PARM_DESC(guard_checking,
        "enable dma sanity checking for buffer overruns");
 
+static bool enable_msi = true;
+module_param(enable_msi, bool, 0444);
+MODULE_PARM_DESC(enable_msi,
+               "enable the use of an msi interrupt if available");
+
 static unsigned int saa7164_devcount;
 
 static DEFINE_MUTEX(devlist);
@@ -1186,6 +1191,39 @@ static int saa7164_thread_function(void *data)
        return 0;
 }
 
+static bool saa7164_enable_msi(struct pci_dev *pci_dev, struct saa7164_dev *dev)
+{
+       int err;
+
+       if (!enable_msi) {
+               printk(KERN_WARNING "%s() MSI disabled by module parameter 'enable_msi'"
+                      , __func__);
+               return false;
+       }
+
+       err = pci_enable_msi(pci_dev);
+
+       if (err) {
+               printk(KERN_ERR "%s() Failed to enable MSI interrupt."
+                       " Falling back to a shared IRQ\n", __func__);
+               return false;
+       }
+
+       /* no error - so request an msi interrupt */
+       err = request_irq(pci_dev->irq, saa7164_irq, 0,
+                                               dev->name, dev);
+
+       if (err) {
+               /* fall back to legacy interrupt */
+               printk(KERN_ERR "%s() Failed to get an MSI interrupt."
+                      " Falling back to a shared IRQ\n", __func__);
+               pci_disable_msi(pci_dev);
+               return false;
+       }
+
+       return true;
+}
+
 static int saa7164_initdev(struct pci_dev *pci_dev,
                           const struct pci_device_id *pci_id)
 {
@@ -1232,13 +1270,22 @@ static int saa7164_initdev(struct pci_dev *pci_dev,
                goto fail_irq;
        }
 
-       err = request_irq(pci_dev->irq, saa7164_irq,
-               IRQF_SHARED, dev->name, dev);
-       if (err < 0) {
-               printk(KERN_ERR "%s: can't get IRQ %d\n", dev->name,
-                       pci_dev->irq);
-               err = -EIO;
-               goto fail_irq;
+       /* irq bit */
+       if (saa7164_enable_msi(pci_dev, dev)) {
+               dev->msi = true;
+       } else {
+               /* if we have an error (i.e. we don't have an interrupt)
+                        or msi is not enabled - fallback to shared interrupt */
+
+               err = request_irq(pci_dev->irq, saa7164_irq,
+                               IRQF_SHARED, dev->name, dev);
+
+               if (err < 0) {
+                       printk(KERN_ERR "%s: can't get IRQ %d\n", dev->name,
+                              pci_dev->irq);
+                       err = -EIO;
+                       goto fail_irq;
+               }
        }
 
        pci_set_drvdata(pci_dev, dev);
@@ -1441,6 +1488,11 @@ static void saa7164_finidev(struct pci_dev *pci_dev)
        /* unregister stuff */
        free_irq(pci_dev->irq, dev);
 
+       if (dev->msi) {
+               pci_disable_msi(pci_dev);
+               dev->msi = false;
+       }
+
        pci_disable_device(pci_dev);
 
        mutex_lock(&devlist);

diff --git a/drivers/media/pci/saa7164/saa7164.h b/drivers/media/pci/saa7164/saa7164.h
index 138f7f9..18906e0 100644 (file)
--- a/drivers/media/pci/saa7164/saa7164.h
+++ b/drivers/media/pci/saa7164/saa7164.h
@@ -464,6 +464,7 @@ struct saa7164_dev {
        /* Interrupt status and ack registers */
        u32 int_status;
        u32 int_ack;
+       bool msi;
 
        struct cmd                      cmds[SAA_CMD_MAX_MSG_UNITS];
        struct mutex                    lock;