On 1/27/23 10:51, Stefan Binding wrote: > From: Richard Fitzgerald <rf@xxxxxxxxxxxxxxxxxxxxx> > > This adds support for using CS42L42 as a SoundWire device. > > SoundWire-specifics are kept separate from the I2S implementation as > much as possible, aiming to limit the risk of breaking the I2C+I2S > support. > > There are some important differences in the silicon behaviour between > I2S and SoundWire mode that are reflected in the implementation: > > - ASP (I2S) most not be used in SoundWire mode because the two interfaces > share pins. > > - The SoundWire capture (record) port only supports 1 channel. It does > not have left-to-right duplication like the ASP. > > - DP2 can only be prepared if the HP has powered-up. DP1 can only be > prepared if the ADC has powered-up. (This ordering restriction does > not exist for ASPs.) The SoundWire core port-prepare step is > triggered by the DAI-link prepare(). This happens before the > codec DAI prepare() or the DAPM sequence so these cannot be used > to enable HP/ADC. Instead the HP/ADC enable/disable are done during > the port_prep callback. > > - The SRCs are an integral part of the audio chain but in silicon their > power control is linked to the ASP. There is no equivalent power link > to SoundWire DPs so the driver must take "manual" control of SRC power. > > - The SoundWire control registers occupy the lower part of the SoundWire > address space so cs42l42 registers are offset by 0x8000 (non-paged) in > SoundWire mode. > > - Register addresses are 8-bit paged in I2C mode but 16-bit unpaged in > SoundWire. > > - Special procedures are needed on register read/writes to (a) ensure > that the previous internal bus transaction has completed, and > (b) handle delayed read results, when the read value could not be > returned within the SoundWire read command. > > There are also some differences in driver implementation between I2S > and SoundWire operation: > > - CS42L42 I2S does not runtime_suspend, but runtime_suspend/resume support > has been added into the driver in SoundWire mode as the most convenient > way to power-up the bus manager and to handle the unattach_request > condition, though the CS42L42 chip does not itself suspend or resume. > > - Intel SoundWire host controllers have a low-power clock-stop mode that > requires resetting all peripherals when resuming. This means that the > interrupt registers will be reset in between the interrupt being > generated and the interrupt being handled, and since the interrupt > status is debounced, these values may not be accurate immediately, > and may cause spurious unplug events before settling. > > - As in I2S mode, the PLL is only used while audio is active because > of clocking quirks in the silicon. For SoundWire the cs42l42_pll_config() > is deferred until the DAI prepare(), to allow the cs42l42_bus_config() > callback to set the SCLK. > > Signed-off-by: Richard Fitzgerald <rf@xxxxxxxxxxxxxxxxxxxxx> > Signed-off-by: Stefan Binding <sbinding@xxxxxxxxxxxxxxxxxxxxx> Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx> > +static int cs42l42_sdw_dai_set_sdw_stream(struct snd_soc_dai *dai, void *sdw_stream, > + int direction) > +{ > + if (!sdw_stream) > + return 0; > + > + if (direction == SNDRV_PCM_STREAM_PLAYBACK) > + dai->playback_dma_data = sdw_stream; > + else > + dai->capture_dma_data = sdw_stream; This may need to be updated to snd_soc_dai_dma_data_set(dai, direction, stream); which is being introduced by Morimoto-san To avoid dependencies this could be updated later.