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SubjectRe: [PATCH v2 2/9] ALSA: hda/i915: Allow override of gpu binding.
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Hey,

On 2023-07-24 12:25, Pierre-Louis Bossart wrote:
>
>
> On 7/21/23 14:19, Péter Ujfalusi wrote:
>>
>>
>> On 19/07/2023 19:41, Maarten Lankhorst wrote:
>>> Selecting CONFIG_DRM selects CONFIG_VIDEO_NOMODESET, which exports
>>> video_firmware_drivers_only(). This can be used as a first
>>> approximation on whether i915 will be available. It's safe to use as
>>> this is only built when CONFIG_SND_HDA_I915 is selected by CONFIG_I915.
>>>
>>> It's not completely fool proof, as you can boot with "nomodeset
>>> i915.modeset=1" to make i915 load regardless, or use
>>> "i915.force_probe=!*" to never load i915, but the common case of
>>> booting with nomodeset to disable all GPU drivers this will work as
>>> intended.
>>>
>>> Because of this, we add an extra module parameter,
>>> snd_hda_core.gpu_bind that can be used to signal users intent.
>>> -1 follows nomodeset, 0 disables binding, 1 forces wait/-EPROBE_DEFER
>>> on binding.
>>
>> Reviewed-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
>>
>>> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
>>> ---
>>> sound/hda/hdac_i915.c | 10 ++++++++++
>>> 1 file changed, 10 insertions(+)
>>>
>>> diff --git a/sound/hda/hdac_i915.c b/sound/hda/hdac_i915.c
>>> index 161a9711cd63e..c32709fa4115f 100644
>>> --- a/sound/hda/hdac_i915.c
>>> +++ b/sound/hda/hdac_i915.c
>>> @@ -11,6 +11,13 @@
>>> #include <sound/hda_i915.h>
>>> #include <sound/hda_register.h>
>>>
>>> +#include <video/nomodeset.h>
>>> +
>>> +static int gpu_bind = -1;
>>> +module_param(gpu_bind, int, 0644);
>>> +MODULE_PARM_DESC(gpu_bind, "Whether to bind sound component to GPU "
>>> + "(1=always, 0=never, -1=on nomodeset(default))");
>>> +
>>> #define IS_HSW_CONTROLLER(pci) (((pci)->device == 0x0a0c) || \
>>> ((pci)->device == 0x0c0c) || \
>>> ((pci)->device == 0x0d0c) || \
>>> @@ -121,6 +128,9 @@ static int i915_gfx_present(struct pci_dev *hdac_pci)
>>> {
>>> struct pci_dev *display_dev = NULL;
>>>
>>> + if (!gpu_bind || (gpu_bind < 0 && video_firmware_drivers_only()))
>>> + return false;
>
>
> Bear with me since I am just going back to work mode but I can't figure
> out what the second part of the test does
>
> bool video_firmware_drivers_only(void)
> {
> return video_nomodeset;
> }
> EXPORT_SYMBOL(video_firmware_drivers_only);
>
> and video_nomodeset=1 by default, so why would we return false when
> gpu_bind = -1?
>
> This seems to be a change of functionality, what am I missing?
video_nomodeset is 0 by default, only when nomodeset is given as
argument is it set to 1. :-)

Cheers,
~Maarten

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