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Date:	Fri, 05 Jun 2015 15:09:48 +1000
From:	Brendan McGrath <redmcg@...mandi.dyndns.org>
To:	Kyle Sanderson <kyle.leet@...il.com>
CC:	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	Hans Verkuil <hans.verkuil@...co.com>,
	Linux-Media <linux-media@...r.kernel.org>,
	Linux-Kernal <linux-kernel@...r.kernel.org>,
	torvalds@...ux-foundation.org
Subject: Re: [PATCHv5] [media] saa7164: use an MSI interrupt when available

Hi Kyle,

Great to hear you haven't had any problems since applying this patch! 
I'm looking forward to seeing it in the Linux master branch too.

Version 5 of the patch has been accepted and committed to the media tree 
by Mauro:
http://git.linuxtv.org/cgit.cgi/media_tree.git/commit/?id=77978089ddc90347644cc057e6b6cd169ac9abd4

I'm guessing it will therefore go in to the main Linux tree with the 
release of kernel version v4.2? (or it can be submitted as a fix for 
v4.1 - but I have no idea how a patch is selected on that criteria).

Hopefully someone can confirm or elaborate.

Regards,
Brendan McGrath


On 05/06/15 14:42, Kyle Sanderson wrote:
> 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@...mandi.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@...nellabs.com>
>> Signed-off-by: Brendan McGrath <redmcg@...mandi.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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