Re: [PATCHv5] [media] saa7164: use an MSI interrupt when available

[Kyle Sanderson <kyle.leet@gmail.com>]

This has been plaguing users for years (there's a number of threads on
the Ubuntu board). I've been using revision 1 of the patch without
issue since early February. This is from having to constantly reboot
the system to flawless recording. If something has been outstanding
from Brendan, please let me know and I'll happily make the requested
changes.

Can we please merge this? There are at-least three consumers in this
thread alone that have confirmed this fixes the saa7164 driver for the
HVR-2250 device.
Kyle.

PS: I can't seem to source out who owns this in the MAINTAINERS file?

On Thu, Apr 9, 2015 at 11:39 PM, Brendan McGrath
<redmcg@redmandi.dyndns.org> wrote:
> 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>
> ---
> Changes since v4:
>   - improved readability by taking on suggestions made by Mauro
>   - the msi variable in the saa7164_dev structure is now a bool
>
> Thanks Mauro - good suggestions and I think I've taken on board all of them.
>
>  drivers/media/pci/saa7164/saa7164-core.c | 66 ++++++++++++++++++++++++++++----
>  drivers/media/pci/saa7164/saa7164.h      |  1 +
>  2 files changed, 60 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/media/pci/saa7164/saa7164-core.c b/drivers/media/pci/saa7164/saa7164-core.c
> index 9cf3c6c..5e4a9f0 100644
> --- 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);
> @@ -1184,6 +1189,39 @@ 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)
>  {
> @@ -1230,13 +1268,22 @@ 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);
> @@ -1439,6 +1486,11 @@ 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 cd1a07c..75a3f51 100644
> --- a/drivers/media/pci/saa7164/saa7164.h
> +++ b/drivers/media/pci/saa7164/saa7164.h
> @@ -459,6 +459,7 @@ 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;
> --
> 1.9.1
>
> --
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