Re: [PATCH 5.15.y] ALSA: hda: Add missing NVIDIA HDA codec IDs

[Sasha Levin <sashal@kernel.org>]

On Wed, Jul 23, 2025 at 11:46:21AM -0500, Daniel Dadap wrote:
>On Wed, Jul 23, 2025 at 10:10:42AM -0400, Sasha Levin wrote:
>> From: Daniel Dadap <ddadap@nvidia.com>
>>
>> [ Upstream commit e0a911ac86857a73182edde9e50d9b4b949b7f01 ]
>>
>> Add codec IDs for several NVIDIA products with HDA controllers to the
>> snd_hda_id_hdmi[] patch table.
>>
>> Signed-off-by: Daniel Dadap <ddadap@nvidia.com>
>> Cc: <stable@vger.kernel.org>
>> Link: https://patch.msgid.link/aF24rqwMKFWoHu12@ddadap-lakeline.nvidia.com
>> Signed-off-by: Takashi Iwai <tiwai@suse.de>
>> [ change patch_tegra234_hdmi function calls to patch_tegra_hdmi ]
>> Signed-off-by: Sasha Levin <sashal@kernel.org>
>> ---
>>  sound/pci/hda/patch_hdmi.c | 19 +++++++++++++++++++
>>  1 file changed, 19 insertions(+)
>>
>> diff --git a/sound/pci/hda/patch_hdmi.c b/sound/pci/hda/patch_hdmi.c
>> index 81025d45306d3..fcd7d94afc5d5 100644
>> --- a/sound/pci/hda/patch_hdmi.c
>> +++ b/sound/pci/hda/patch_hdmi.c
>> @@ -4364,6 +4364,8 @@ HDA_CODEC_ENTRY(0x10de002d, "Tegra186 HDMI/DP0", patch_tegra_hdmi),
>>  HDA_CODEC_ENTRY(0x10de002e, "Tegra186 HDMI/DP1", patch_tegra_hdmi),
>>  HDA_CODEC_ENTRY(0x10de002f, "Tegra194 HDMI/DP2", patch_tegra_hdmi),
>>  HDA_CODEC_ENTRY(0x10de0030, "Tegra194 HDMI/DP3", patch_tegra_hdmi),
>> +HDA_CODEC_ENTRY(0x10de0033, "SoC 33 HDMI/DP",	patch_tegra_hdmi),
>> +HDA_CODEC_ENTRY(0x10de0035, "SoC 35 HDMI/DP",	patch_tegra_hdmi),
>
>I tested a modified snd-hda-codec-hdmi.ko which patched one of these to
>patch_tegra_hdmi instead of patch_tegra234_hdmi, and it still worked
>correctly as far as I could tell with a few brief checks. However, it
>seems like patch_nvhdmi might be a better match, at least based on how
>it seems to behave with DP MST, so if we don't decide to drop the codec
>entries for 0x10de0033 and 0x10de0035 in the older branches it might be
>good to use patch_nvhdmi.

Hmm...

I've used patch_tegra_hdmi because from my understanding of the code,
Tegra SoCs require explicit format notification through NVIDIA AFG
scratch registers. The key mechanism is in tegra_hdmi_set_format() which
writes the HDA format to NVIDIA_SET_SCRATCH0_BYTE[0-1] and toggles
NVIDIA_SCRATCH_VALID (bit 30) in NVIDIA_SET_SCRATCH0_BYTE3.

patch_nvhdmi doesn't seem to deal with this at all.

>It probably does make more sense to drop the SoC codec entries for the
>backports, the more I think about it. It makes sense to backport dGPU
>codec entries since somebody could put an add-in-board into an existing
>system running an LTS kernel, but for new SoCs you'd want the kernel to
>be recent enough to support all of the hardware on the system. Notably,
>we don't seem to have backported HDA codec entries for other SoCs like
>the T234 that patch_tegra234_hdmi was added for in the first place.

On our end we'd prefer to keep this align with upstream as much as
possible: it will make future patches easier to apply without manual
modifications.

If leaving them in there is harmless (and only unnecessary), I'd rather
just leave it there.

-- 
Thanks,
Sasha