Re: [PATCH 4/5] i2c: qcom-cci: Add OPP table support and enforce FAST_PLUS requirements

Stephan Gerhold
2025-09-08T08:37:02Z

On Thu, Sep 04, 2025 at 04:31:23PM +0200, Konrad Dybcio wrote:
> From: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
>
> The CCI clock has voltage requirements, which need to be described
> through an OPP table.
>
> The 1 MHz FAST_PLUS mode requires the CCI core clock runs at 37,5 MHz
> (which is a value common across all SoCs), since it's not possible to
> reach the required timings with the default 19.2 MHz rate.
>
> Address both issues by introducing an OPP table and using it to vote
> for the faster rate.
>
> Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>

Using an OPP table for a single static rate that remains the same over
the whole lifetime of the driver feels like overkill to me. Couldn't you
just put the "required-opps" directly into the device node so that it is
automatically applied when the device goes in/out of runtime suspend?

And since you need to make DT additions anyway, couldn't you just use
"assigned-clock-rates" to avoid the need for a driver patch entirely? We
use that for e.g. USB clocks as well.

Thanks,
Stephan