Re: [PATCH v2 2/2] ASoC: Intel: Skylake: Add Cometlake PCI IDs - Pierre-Louis Bossart

From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
To: Evan Green <evgreen@chromium.org>
Cc: Liam Girdwood <liam.r.girdwood@linux.intel.com>,
	Mark Brown <broonie@kernel.org>, Naveen M <naveen.m@intel.com>,
	Sathya Prakash <sathya.prakash.m.r@intel.com>,
	Ben Zhang <benzh@chromium.org>, Rajat Jain <rajatja@chromium.org>,
	Jaroslav Kysela <perex@perex.cz>,
	alsa-devel@alsa-project.org,
	Rakesh Ughreja <rakesh.a.ughreja@intel.com>,
	Guenter Roeck <groeck@chromium.org>, Yu Zhao <yuzhao@google.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Takashi Iwai <tiwai@suse.com>, Jenny TC <jenny.tc@intel.com>,
	Jie Yang <yang.jie@linux.intel.com>
Subject: Re: [PATCH v2 2/2] ASoC: Intel: Skylake: Add Cometlake PCI IDs
Date: Wed, 8 May 2019 12:04:27 -0500	[thread overview]
Message-ID: <6fd9ca2b-dcf6-801f-209e-11eba59203fe@linux.intel.com> (raw)
In-Reply-To: <CAE=gft4sDo1cLeU8Cm1CRZu2PzVG0iu-b7UaWxWVrsUeZ=SYhQ@mail.gmail.com>

On 5/8/19 11:51 AM, Evan Green wrote:
> On Tue, May 7, 2019 at 3:31 PM Pierre-Louis Bossart
> <pierre-louis.bossart@linux.intel.com> wrote:
>>
>> On 5/7/19 4:53 PM, Evan Green wrote:
>>> Add PCI IDs for Intel CometLake platforms, which from a software
>>> point of view are extremely similar to Cannonlake platforms.
>>
>> Humm, I have mixed feelings here.
>>
>> Yes the hardware is nearly identical, with the exception of one detail
>> that's not visible to the kernel, but there is no support for DMICs with
>> the Skylake driver w/ HDaudio, and Chrome platforms are only going with
>> SOF, so is it wise to add these two CometLake platforms to the default
>> SND_SOC_INTEL_SKYLAKE selector, which is used by a number of distributions?
>>
>> I don't mind if we add those PCI IDs and people use this driver if they
>> wish to, but it may be time for an explicit opt-in? The
>> SND_SOC_INTEL_SKYLAKE definition should even be pruned to mean SKL, APL,
>> KBL and GLK, and we can add DMI-based quirks for e.g. the Up2 board and
>> GLK Chromebooks which work with SOF.
> 
> I don't have the context here, so feel free to ignore me. But it seems
> like such a tiny amount of extra bits to add to make Cometlake work,
> and then there's no hassle for the distributions when Cometlake
> devices start showing up in the wild. So while things are more or less
> the same, why not continue piggypacking off the default?
> Or are you saying that the lack of DMIC support means the default
> should be to use a different driver?

Yes, it's the latter case, SOF will be the only driver supporting DMICs 
on CometLake, so it'd be better to avoid creating a conflict with SOF or 
enabling a configuration by default which is known to have restrictions. 
It's fine to add the CML IDs, but better avoid adding CML under the 
SKYLAKE all-you-can-eat selector.