[PATCH] ASoC: Intel: haswell: Power transition refactor

[Ross Zwisler]

On Mon, Mar 30, 2020 at 09:45:20PM +0200, Cezary Rojewski wrote:
> Update D0 <-> D3 sequence to correctly transition hardware and DSP core
> from and to D3. On top of that, set SHIM registers to their recommended
> defaults during D0 and D3 proceduces as HW does not reset registers for
> us.
> 
> Connected to:
> [alsa-devel][BUG] bdw-rt5650 DSP boot timeout
> https://mailman.alsa-project.org/pipermail/alsa-devel/2019-July/153098.html
> 
> Github issue ticket reference:
> https://github.com/thesofproject/linux/pull/1842
> 
> Tested on:
> - BDW-Y RVP with rt286
> - SAMUS with rt5677
> 
> Proposed solution (both in July 2019 and on github):
> 'Revert "ASoC: Intel: Work around to fix HW d3 potential crash issue"'
> is NAKed as it only covers the problem up and actually brings back the
> undefined behavior: some registers (e.g.: APLLSE) are describing LPT
> offsets rather than WPT ones. In consequence, during power-transitions
> driver issues incorrect writes and leaves the regs of interest alone.
> 
> Existing patch - the non-revert - does not resolve the HW D3 issue at
> all as it ignores the recommended sequence and does not initialize
> hardware registers as expected. And thus, leaving things as are is also
> unacceptable.
> 
> Signed-off-by: Cezary Rojewski <cezary.rojewski at intel.com>

Tested-by: Ross Zwisler <zwisler at google.com>