linux-kernel - Re: [PATCH 12/16] clk: qcom: clk-krait: add 8064 errata workaround

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Message-Id: <20220315213431.DB6C4C340EE@smtp.kernel.org>
Date:   Tue, 15 Mar 2022 14:34:30 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Ansuel Smith <ansuelsmth@...il.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        Prashant Gaikwad <pgaikwad@...dia.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-tegra@...r.kernel.org
Subject: Re: [PATCH 12/16] clk: qcom: clk-krait: add 8064 errata workaround

Quoting Ansuel Smith (2022-03-14 05:43:20)
> On Mon, Mar 14, 2022 at 11:20:21AM +0300, Dmitry Baryshkov wrote:
> > On 13/03/2022 22:04, Ansuel Smith wrote:
> > > Add 8064 errata workaround where the sec_src clock gating needs to be
> > 
> > Could you please be more specific whether the errata applies only to the
> > ipq8064 or to the apq8064 too? 8064 is not specific enough.
> >
> 
> That's a good question... Problem is that we really don't know the
> answer. This errata comes from qsdk on an old sourcecode. I assume this
> is specific to ipq8064 and apq8064 have different mux configuration.
> 

I think it was some glitch that happened when the automatic clk gating
was enabled during a switch. The automatic clk gating didn't know that
software was running and switching the input so it killed the CPU and
stopped the clk. That lead to hangs and super badness. I assume it was
applicable to apq8064 as well because ipq8064 is basically apq8064 with
the multimedia subsystem replaced by the networking subsystem. Also I
wouldn't remember all these details because I worked on apq8064 but not
so much on ipq8064 :)