linux-kernel - Re: [PATCH v2 2/9] ALSA: hda/i915: Allow override of gpu binding.

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Message-ID: <9b285ede-eaeb-40a2-086d-30cf74185784@linux.intel.com>
Date:   Fri, 21 Jul 2023 15:19:53 +0300
From:   Péter Ujfalusi <peter.ujfalusi@...ux.intel.com>
To:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        alsa-devel@...a-project.org
Cc:     sound-open-firmware@...a-project.org, linux-kernel@...r.kernel.org,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Cezary Rojewski <cezary.rojewski@...el.com>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Liam Girdwood <liam.r.girdwood@...ux.intel.com>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
        Mark Brown <broonie@...nel.org>,
        Daniel Baluta <daniel.baluta@....com>
Subject: Re: [PATCH v2 2/9] ALSA: hda/i915: Allow override of gpu binding.



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@...ux.intel.com>

> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@...ux.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;
> +
>  	for_each_pci_dev(display_dev) {
>  		if (display_dev->vendor == PCI_VENDOR_ID_INTEL &&
>  		    (display_dev->class >> 16) == PCI_BASE_CLASS_DISPLAY &&

-- 
Péter