Re: Fedora 34 Change: SOF as default audio driver for Intel LPE hardware (Self-Contained Change proposal)

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On Mon, Jan 18, 2021 at 03:49:58PM +0000, Peter Robinson wrote:
> On Mon, Jan 18, 2021 at 3:20 PM Ben Cotton <bcotton@xxxxxxxxxx> wrote:
> >
> > https://fedoraproject.org/wiki/Changes/SofDefaultForIntelLpe
> >
> >
> > == Summary ==
> > Intel LPE audio hardware has 2 drivers in the mainline kernel the SST
> > driver and the SOF driver, switch the default driver from SST to SOF.
> >
> > == Owner ==
> > * Name: [[User:jwrdegoede| Hans de Goede]]
> > * Email: hdegoede@xxxxxxxxxx
> >
> >
> > == Detailed Description ==
> >
> > Intel x86 hardware based on the Bay Trail-T and Cherry Trails SoCs
> > does not come with the standard Intel HDA audio hardware. Instead it
> > has an audio block called the Low Power Engine or LPE. The LPE block
> > needs to have firmware loaded into it to function. There are 2
> > firmwares available the old proprietary SST firmware and recently the
> > open source SOF firmware has been released for the LPE engine.
> >
> > There are also 2 kernel drivers for the LPE block, one for each
> > firmware, so we have a SST driver and a SOF driver. The upstream Intel
> > developers of these drivers, who are also part of the SOF team want to
> > deprecate and eventually remove the old SST driver in favor of the SOF
> > driver. Starting with the 5.11 kernel it is possible to build both
> > drivers into a single kernel and select which one will actually bind
> > to the LPE block using a kernel commandline parameter.
> >
> > ATM the upstream default is the old SST driver, to avoid regressions.
> > This Fedora change will entail carrying a downstream patch which flips
> > the default to the SOF driver. This is being done in conclave with the
> > upstream devs who would like to see more testing of the SOF driver.
> > The upstream devs believe that the SOF driver is ready to replace the
> > SST driver, but they would appreciate this being tested by Fedora
> > first, before they flip the default for everyone.
> >
> >
> > == Benefit to Fedora ==
> >
> > By consciously making the switch now, with extensive testing and
> > monitoring the situation we can safely make the switch without
> > regressions hitting users of the Fedora stable releases. Whereas if we
> > just wait for upstream to flip the default, then this may very well
> > land in the middle of a stable release when we rebase the kernel.
> >
> > This helps strengthen our relationship with the upstream developers
> > and falls under the "First" part of the "Four Foundations".
> >
> > This stops us from depending in the proprietary SST firmware-blobs,
> > replacing them with the Open Source SOF firmware, matching the
> > "Freedom" part of the "Four Foundations".
> >
> > == Scope ==
> > * Proposal owners: This will require a small downstream kernel patch
> > to change the default driver when both are built (or an upstream patch
> > to make the default configurable). That's it, no other changes are
> > required.
> > * Other developers: N/A (not a System Wide Change)
> > * Release engineering: N/A (not a System Wide Change)
> > * Policies and guidelines: N/A (not a System Wide Change)
> > * Trademark approval: N/A (not needed for this Change)
> > * Alignment with Objectives: This falls under the "First" part of the
> > "Four Foundations".
> >
> > == Upgrade/compatibility impact ==
> > The switch will automatically be made when booting a Fedora 34 kernel.
> >
> > == How To Test ==
> > I (Hans de Goede) have an extensive collection of affected hardware.
> > The audio setup on these devices consists of the LPE block itself
> > combined with an external audio-codec. There are a number of
> > audio-codecs used / supported on these boards. The LPE block has 2
> > audio-links (called SSP0 and SSP2) and some of the codecs have 2
> > audio-links (called AIF1 and AIF2) not each board uses the same
> > audio-link on each side.
> >
> > I plan to run the below test-plan on devices with the following SoC /
> > codec / link combinations:
> >
> > * Bay Trail (CR) / RT5640  / SSP0<->AIF1
> > * Bay Trail (CR) / RT5640  / SSP0<->AIF2
> > * Bay Trail      / RT5640  / SSP2<->AIF1
> > * Cherry Trail   / RT5640  / SSP2<->AIF1
> > * Cherry Trail   / RT5645  / SSP2
> > * Bay Trail (CR) / RT5651  / SSP0<->AIF1
> > * Cherry Trail   / RT5651  / SSP2<->AIF1
> > * Bay Trail      / RT5672  / SSP2
> > * Bay Trail (CR) / ESS8316 / SSP0
> > * Cherry Trail   / ESS8316 / SSP2
> > * Cherry Trail   / NAU8824 / SSP2
> 
> Does this cover newer generations like Apollo Lake?

Also: is there some easy command (something bar grep something) that
users could execute to test if they have the affected hardware?
Please put it in the Change page.

> > Each of these will be tested according to the following test-plan:
> >
> > # Test speakers.
> > # Test internal mic.
> > # Plugin headset, test headphones.
> > # Test headset-mic
> > # Stop all audio, suspend + resume, test speakers.
> > # suspend + resume while playing audio, audio should resume playing
> > after resume.
> >
> > Users who want to test this and who have the affected hardware can
> > also use this test-plan to test.
> >
> > == User Experience ==
> > The SST driver has some suspend/resume problems around suspending with
> > audio playing. The SOF driver resolves these. Other then that the
> > user-experience should be unchanged.
> >
> > == Dependencies ==
> > N/A (not a System Wide Change)
> >
> > == Contingency Plan ==
> > We can simply drop the patch flipping the default to get back to the
> > F33 state of things.
> >
> > * Contingency mechanism: Revert the change
> > * Contingency deadline: Beta release
> > * Blocks release? No
> >
> > == Documentation ==
> > N/A (not a System Wide Change)
> >
> > == Release Notes ==
> > FIXME: TODO

Zbyszek
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