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SubjectRe: [PATCH] clk: qcom: gdsc: Ensure regulator init state matches GDSC state
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Quoting Bjorn Andersson (2021-06-25 15:54:14)
> As GDSCs are registered and found to be already enabled
> gdsc_toggle_logic() will be invoked for votable GDSCs and ensure that
> the vote is matching the hardware state. Part of this the related
> regulator will be enabled.
>
> But for non-votable GDSCs the regulator and GDSC status will be out of
> sync and as the GDSC is later disabled regulator_disable() will face an
> unbalanced enable-count, or something might turn off the supply under
> the feet of the GDSC.
>
> So ensure that the regulator is enabled even for non-votable GDSCs.
>
> Cc: stable@vger.kernel.org
> Fixes: 37416e554961 ("clk: qcom: gdsc: Handle GDSC regulator supplies")
> Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
> ---
> drivers/clk/qcom/gdsc.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/clk/qcom/gdsc.c b/drivers/clk/qcom/gdsc.c
> index 51ed640e527b..f7e7759cdb90 100644
> --- a/drivers/clk/qcom/gdsc.c
> +++ b/drivers/clk/qcom/gdsc.c
> @@ -359,10 +359,17 @@ static int gdsc_init(struct gdsc *sc)
>
> /*
> * Votable GDSCs can be ON due to Vote from other masters.
> - * If a Votable GDSC is ON, make sure we have a Vote.
> + * If a Votable GDSC is ON, make sure we have a Vote. If
> + * non-votable, ensure that the supply is kept enabled (as
> + * is done by gdsc_enable).
> */
> - if ((sc->flags & VOTABLE) && on)
> + if ((sc->flags & VOTABLE) && on) {
> gdsc_enable(&sc->pd);
> + } else if (on) {
> + ret = regulator_enable(sc->rsupply);
> + if (ret < 0)
> + return ret;

Looking at this makes me think we've messed something up with
gdsc_enable() being called or cherry-picking the regulator enable (and
other stuff in this gdsc_init()) out of the enable path. Maybe we should
have a followup patch that replaces the gdsc_enable() with
gdsc_toggle_logic(sc, GDSC_ON) so that we know it isn't doing anything
else during init like asserting a reset when presumably all we want to
do is toggle the enable bit to assert our vote.

And I notice that we already call gdsc_toggle_logic() in gdsc_init(), so
then we'll have a double regulator_enable() in the case of PWRSTS_ON?
And then if the flag is ALWAYS_ON we'll call regulator_enable() yet
again, but luckily only if it isn't on initially, phew! This code is
quite twisted.

It would be super nice to make it more like

if (on) {
/* It was on in hardware, sync kernel state */
regulator_enable();

if (votable)
write bit, why do any wait?

if (retain ff)
write bit
} else if (always_on) {
/* Force on */
gdsc_enable();
on = true;
}

if (on || ...)

> + }
>
> /*
> * Make sure the retain bit is set if the GDSC is already on, otherwise

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