linux-kernel - Re: [PATCH] soc: qcom: rpmh-rsc: Don't use ktime for timeout in write_tcs_reg

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Date:   Thu, 18 Jun 2020 14:52:32 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Maulik Shah <mkshah@...eaurora.org>,
        Stephen Boyd <swboyd@...omium.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] soc: qcom: rpmh-rsc: Don't use ktime for timeout in write_tcs_reg_sync()

Bjorn and Andy,

On Thu, May 28, 2020 at 7:48 AM Douglas Anderson <dianders@...omium.org> wrote:
>
> The write_tcs_reg_sync() may be called after timekeeping is suspended
> so it's not OK to use ktime.  The readl_poll_timeout_atomic() macro
> implicitly uses ktime.  This was causing a warning at suspend time.
>
> Change to just loop 1000000 times with a delay of 1 us between loops.
> This may give a timeout of more than 1 second but never less and is
> safe even if timekeeping is suspended.
>
> NOTE: I don't have any actual evidence that we need to loop here.
> It's possibly that all we really need to do is just read the value
> back to ensure that the pipes are cleaned and the looping/comparing is
> totally not needed.  I never saw the loop being needed in my tests.
> However, the loop shouldn't hurt.
>
> Fixes: 91160150aba0 ("soc: qcom: rpmh-rsc: Timeout after 1 second in write_tcs_reg_sync()")
> Reported-by: Maulik Shah <mkshah@...eaurora.org>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
>
>  drivers/soc/qcom/rpmh-rsc.c | 18 +++++++++++++-----
>  1 file changed, 13 insertions(+), 5 deletions(-)

Is it a good time to land this change now that -rc1 has come out?
It'd be nice to get this resolved.

Thanks!

-Doug