linux-kernel - Re: [PATCH v4 3/3] clk: qcom: lpasscc-sc7180: Re-configure the PLL in case lost

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Message-ID: <CAD=FV=WAVoZ59p51HxBwBNXsXcirRbUAjeGuZ4T9G-O7Tvzqfw@mail.gmail.com>
Date:   Fri, 16 Oct 2020 20:17:56 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Stephen Boyd <sboyd@...nel.org>
Cc:     Taniya Das <tdas@...eaurora.org>,
        David Brown <david.brown@...aro.org>,
        "open list:ARM/QUALCOMM SUPPORT" <linux-soc@...r.kernel.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        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 v4 3/3] clk: qcom: lpasscc-sc7180: Re-configure the PLL in
 case lost

Hi,

On Fri, Oct 16, 2020 at 7:01 PM Stephen Boyd <sboyd@...nel.org> wrote:
>
> Quoting Stephen Boyd (2020-10-15 20:16:27)
> > Quoting Douglas Anderson (2020-10-14 17:13:29)
> > > From: Taniya Das <tdas@...eaurora.org>
> > >
> > > In the case where the PLL configuration is lost, then the pm runtime
> > > resume will reconfigure before usage.
> >
> > Taniya, this commit needs a lot more describing than one sentence. I see
> > that the PLL's L value is reset at boot, but only once. That seems to be
> > because the bootloader I have doesn't set bit 11 for the RETAIN_FF bit
> > on the lpass_core_hm_gdsc. Once the gdsc is turned off the first time,
> > the PLL settings are lost and the L val is reset to 0. That makes sense
> > because RETAIN_FF isn't set. This also means the other register writes
> > during probe are lost during the first suspend of the lpass core clk
> > controller. Then when the GDSC is turned on the next time for this clk
> > controller  being runtime resumed we will set the retain bit and then
> > configure the PLL again. BTW, I see that runtime PM is called for this
> > clk controller for all the clk operations. Maybe there should be some
> > auto suspend timeout so that we're not toggling the gdsc constantly?
> >
> > I hacked up the GDSC code to set the bit at gdsc registration time and
> > it seems to fix the problem I'm seeing (i.e. that the PLL is stuck,
> > which should also be in the commit text here). When I try to set the bit
> > in the bootloader though my kernel won't boot. I guess something is
> > hanging the system if I enable the retain bit in the GDSC?
> >
>
> After hacking on this for some time it looks like we can apply this
> patch instead and things are good. The first two patches in this series
> look mostly good to me minus some nitpicks so please resend.

By this you mean the two newlines you mentioned on
<https://crrev.com/c/2473610>, right?  I think all the rest of your
comments were on patch #3 (this patch) which I think we're dropping.

I'm happy to repost a v5 of just patches #1 and #2 with the newlines
fixed next week, or I'm happy if you want to fix them when applying as
you alluded to on the Chrome OS gerrit.  Just let me know.  I just
want to make sure I'm not missing some other nits before I post the
v5.  ;-)

-Doug