Re: [PATCH] clk: qcom: gdsc: Keep RETAIN_FF bit set if gdsc is already on

[Doug Anderson]

Hi,

On Fri, Oct 16, 2020 at 7:01 PM Stephen Boyd <sboyd@xxxxxxxxxx> wrote:
>
> If the GDSC is enabled out of boot but doesn't have the retain ff bit
> set we will get confusing results where the registers that are powered
> by the GDSC lose their contents on the first power off of the GDSC but
> thereafter they retain their contents. This is because gdsc_init() fails
> to make sure the RETAIN_FF bit is set when it probes the GDSC the first
> time and thus powering off the GDSC causes the register contents to be
> reset. We do set the RETAIN_FF bit the next time we power on the GDSC,
> see gdsc_enable(), so that subsequent GDSC power off's don't lose
> register contents state.
>
> Forcibly set the bit at device probe time so that the kernel's assumed
> view of the GDSC is consistent with the state of the hardware. This
> fixes a problem where the audio PLL doesn't work on sc7180 when the
> bootloader leaves the lpass_core_hm GDSC enabled at boot (e.g. to make a
> noise) but critically doesn't set the RETAIN_FF bit.
>
> Cc: Douglas Anderson <dianders@xxxxxxxxxxxx>
> Cc: Taniya Das <tdas@xxxxxxxxxxxxxx>
> Cc: Rajendra Nayak <rnayak@xxxxxxxxxxxxxx>
> Fixes: 173722995cdb ("clk: qcom: gdsc: Add support to enable retention of GSDCR")
> Signed-off-by: Stephen Boyd <sboyd@xxxxxxxxxx>
> ---
>  drivers/clk/qcom/gdsc.c | 8 ++++++++
>  1 file changed, 8 insertions(+)

Reviewed-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
Tested-by: Douglas Anderson <dianders@xxxxxxxxxxxx>