linux-kernel - Re: [PATCH] clk: qcom: clk-rpmh: Wait for completion when enabling clocks

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Date:   Wed, 12 Aug 2020 06:52:05 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Stephen Boyd <sboyd@...nel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Cc:     Mike Tipton <mdtipton@...eaurora.org>,
        Taniya Das <tdas@...eaurora.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        Andy Gross <agross@...nel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] clk: qcom: clk-rpmh: Wait for completion when enabling clocks

Hi,

On Mon, Mar 9, 2020 at 2:11 PM Stephen Boyd <sboyd@...nel.org> wrote:
>
> Quoting Mike Tipton (2020-02-14 18:12:32)
> > The current implementation always uses rpmh_write_async, which doesn't
> > wait for completion. That's fine for disable requests since there's no
> > immediate need for the clocks and they can be disabled in the
> > background. However, for enable requests we need to ensure the clocks
> > are actually enabled before returning to the client. Otherwise, clients
> > can end up accessing their HW before the necessary clocks are enabled,
> > which can lead to bus errors.
> >
> > Use the synchronous version of this API (rpmh_write) for enable requests
> > in the active set to ensure completion.
> >
> > Completion isn't required for sleep/wake sets, since they don't take
> > effect until after we enter sleep. All rpmh requests are automatically
> > flushed prior to entering sleep.
> >
> > Fixes: 9c7e47025a6b ("clk: qcom: clk-rpmh: Add QCOM RPMh clock driver")
> > Signed-off-by: Mike Tipton <mdtipton@...eaurora.org>
> > ---
>
> Applied to clk-next but I squashed in some changes to make it easier for
> me to read.

This landed upstream as commit dad4e7fda4bd ("clk: qcom: clk-rpmh:
Wait for completion when enabling clocks") but seemed to have missed
stable.  Can stable pick it up?  It has a Fixes tag so presumably it
should be easy to track down where it needs to go.

Thanks!

-Doug