On Tue, Apr 25, 2023 at 06:02:20PM +0200, Paweł Anikiel wrote:
On Fri, Apr 14, 2023 at 7:35 PM Mark Brown broonie@kernel.org wrote:
On Fri, Apr 14, 2023 at 04:01:59PM +0200, Paweł Anikiel wrote:
Apply a workaround for what seems to be a hardware quirk: when using an external MCLK signal, powering on Output and DAC for the first time produces output distortions unless they're powered together with whole chip power.
This doesn't seem coherent, these are multiple register writes so clearly can't be done at the same moment as initial power on. Clearly there's some other constraint here.
The "at the same time" part is done by writing multiple bits at once to SSM2602_PWR. But before that, SSM2602_ACTIVE has to be set, and then the chip is reset (SSM2602_RESET) to power everything down again.
So you need to power up the chip then do a register write sequence - that's noticably different to what the description says.
Here are some sequences run at the very start before a sw reset (and later using one of the NOT OK sequences from above):
ssmset 0x09 0x01 # core ssmset 0x06 0x07 # chip, out, dac OK
I can't tell what any of this is trying to say, especially given all the magic numbers, and obviously no actual use of the driver should be writing directly to the register map.
These are shell commands run from userspace (with no ssm2602 driver present in the kernel). ssmset is a wrapper for the i2cset command: ssmset() { i2cset -y 0 0x1a $(($1*2)) $2 } I definitely should have made that more clear.
Do you think these logs are worth adding? If so, I'll improve the explanation what these mean.
Probably? Since I couldn't really follow what these were trying to tell me it's a bit hard to say. It looks like you worked this out yourself rather than using an erratum so documenting where the workaround comes from seems useful.