10 Feb
2022
10 Feb
'22
5:04 p.m.
On Wed, 9 Feb 2022, Mark Brown wrote:
In this case it was the ADAU1761 driver and it was several years ago and I don't know if it still is an issue. Basically the sequence was something like:
- System boots up.
- Codec is configured (I think it was the sample rate, but it could have been the format or some other I2S parameter) to something that is non default.
- System reboots. Since the codec has no means of getting reset, it retains all its register values.
- This time, an attempt is made to configure the codec with the default sample rate. Since the driver believes the default is already set it does not attempt to write anything, although looking at regmap_write() now I'm not sure how this could be the case.
update_bits() could also trigger this if it thinks the value didn't change, but that's at a higher level before it ever gets as far as trying to do the write and unrelated to the cache (it will also suppress redundant writes with no cache present).
Right, that sound even more familiar.
/Ricard
--
Ricard Wolf Wanderlof ricardw(at)axis.com
Axis Communications AB, Lund, Sweden www.axis.com
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