[alsa-devel] [PATCH 7/8] ASoC: tegra: config fifos on hw_param changes

[Ben Dooks]

On 2019-09-18 10:14, Jon Hunter wrote:
> On 17/09/2019 19:12, Ben Dooks wrote:
>> If the hw_params uses a different bit or channel count, then we
>> need to change both the I2S unit's CIF configuration as well as
>> the APBIF one.
>> 
>> To allow changing the APBIF, add a call to reconfigure the RX or
>> TX FIFO without changing the DMA or allocation, and get the I2S
>> driver to call it once the hw params have been calculate.
>> 
>> Signed-off-by: Ben Dooks <ben.dooks at codethink.co.uk>
>> ---
>>  sound/soc/tegra/tegra30_ahub.c | 114 
>> ++++++++++++++++++---------------
>>  sound/soc/tegra/tegra30_ahub.h |   5 ++
>>  sound/soc/tegra/tegra30_i2s.c  |   2 +
>>  3 files changed, 69 insertions(+), 52 deletions(-)
>> 
>> diff --git a/sound/soc/tegra/tegra30_ahub.c 
>> b/sound/soc/tegra/tegra30_ahub.c
>> index 952381260dc3..58e05ceb86da 100644
>> --- a/sound/soc/tegra/tegra30_ahub.c
>> +++ b/sound/soc/tegra/tegra30_ahub.c
>> @@ -84,12 +84,40 @@ static int tegra30_ahub_runtime_resume(struct 
>> device *dev)
>>  	return 0;
>>  }
>> 
>> +int tegra30_ahub_setup_rx_fifo(enum tegra30_ahub_rxcif rxcif,
>> +			       struct tegra30_ahub_cif_conf *cif_conf)
>> +{
>> +	int channel = rxcif - TEGRA30_AHUB_RXCIF_APBIF_RX0;
>> +	u32 reg, val;
>> +
>> +	pm_runtime_get_sync(ahub->dev);
>> +
>> +	reg = TEGRA30_AHUB_CHANNEL_CTRL +
>> +	      (channel * TEGRA30_AHUB_CHANNEL_CTRL_STRIDE);
>> +	val = tegra30_apbif_read(reg);
>> +	val &= ~(TEGRA30_AHUB_CHANNEL_CTRL_RX_THRESHOLD_MASK |
>> +		 TEGRA30_AHUB_CHANNEL_CTRL_RX_PACK_MASK);
>> +	val |= (7 << TEGRA30_AHUB_CHANNEL_CTRL_RX_THRESHOLD_SHIFT) |
>> +	       TEGRA30_AHUB_CHANNEL_CTRL_RX_PACK_EN |
>> +	       TEGRA30_AHUB_CHANNEL_CTRL_RX_PACK_16;
>> +	tegra30_apbif_write(reg, val);
> 
> Aren't you just programming the same value to the APBIF here that was
> previously programmed by the allocate function? I don't see the point 
> in
> moving this? What am I missing here?

IIRC, this was due to trying different types of playback with a 4ch 
32bit
sound output. The ahub and the i2s unit don't have to agreet.