[alsa-devel] [RFC 00/10] Enable HDA Codec support on Intel Platforms (Series2)

[Vinod Koul]

On Sun, Dec 03, 2017 at 09:44:56PM -0600, Pierre-Louis Bossart wrote:
> On 12/3/17 9:22 PM, Vinod Koul wrote:
> >On Sun, Dec 03, 2017 at 09:15:21PM -0600, Pierre-Louis Bossart wrote:
> >>On 12/3/17 11:20 AM, Vinod Koul wrote:
> >>>On Fri, Dec 01, 2017 at 09:03:25PM +0100, Takashi Iwai wrote:
> >>>>>>>FIXME:
> >>>>>>>- KConfig changes does not look right, but I could not think of any proper
> >>>>>>>    way without making changes into legacy HDA codec driver. So need some
> >>>>>>>    help on this topic.
> >>>>>>
> >>>>>>And this is another big issue.  As long as you don't allow build both,
> >>>>>>it never flies with distros, and it means no dramatic improvement of
> >>>>>>the situation, either.
> >>>>>>
> >>>>>>IOW, we have to make the codec driver working on both controller/bus
> >>>>>>implementations, and it essentially means to rewrite the HD-audio
> >>>>>>codec plumbing code.  Currently, it's a kind of half-baked state, and
> >>>>>>we need to cast to unified form.
> >>>>>
> >>>>>Before going into codec support, should we first deal with the
> >>>>>selection of the ASoC/Legacy mode for the controller side of things?
> >>>>>Even with basic HDMI/iDisp cases, we don't have a clean solution
> >>>>>today. When I worked on the late Joule platform, there was no fallback
> >>>>>mode which forced a recompilation depending on BIOS settings.
> >>>>>My understanding is that there is no support for multiple drivers
> >>>>>registering for the same PCI ID, I believe we'll have to define a
> >>>>>top-level wrapper which arbitrates internally based on BIOS settings
> >>>>>and user/distro preferences which mode is selected.
> >>>>
> >>>>True, we need to sort out that.  But the selection of the card-level
> >>>>driver can be relatively easily done in a manual way, either via
> >>>>blacklisting or by common module options.  Currently AMDGPU and radeon
> >>>>drivers are in such situation, for example.
> >>>>
> >>>>A common single switch, or at best the automatic arbitration would be
> >>>>preferred, of course, though.
> >>>
> >>>The switch is again short term as we should progress and move towards one
> >>>solution whilst deprecating the other, so that way this makes a simple
> >>>solution and helps in transition, change flag defaults and deprecate.
> >>
> >>Sorry, I don't get your point. Are you saying the legacy would be
> >>deprecated? that was never my understanding, Rakesh's patches only make it
> >>easier to use the DSP in combination with an HDaudio codec, but if the DSP
> >>is not present the legacy is the fallback, no?
> >
> >for now yes, but what prevents us from supporting coupled mode when DSP is
> >disabled :)
> 
> That gets complicated. you'd have
> 1. DSP-based ASoC driver for SKL+ w/ DSP
> 2. coupled-mode ASoC driver for SKL+ w/o DSP
> 3. legacy for pre-SKL platforms.
> 
> I don't see what simplification this brings, it's complicated enough with 1.
> and 3, and legacy is not going away.

in long term we _need_ to converge. 1 and 2 should be same driver detecting
presence of DSP dynamically and doing DSP based or coupled mode.

3 would be separate drivers for different PCI IDs so no conflict.

Thanks
-- 
~Vinod