linux-kernel - Re: [PATCH v2] cpufreq: sun50i: Fix CPU speed bin detection

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Message-ID: <20191105093717.q5ixjjsnb3aqzxql@vireshk-i7>
Date:   Tue, 5 Nov 2019 15:07:17 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Maxime Ripard <mripard@...nel.org>
Cc:     Ondrej Jirman <megous@...ous.com>, linux-sunxi@...glegroups.com,
        Yangtao Li <tiny.windzz@...il.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Chen-Yu Tsai <wens@...e.org>,
        "open list:ALLWINNER CPUFREQ DRIVER" <linux-pm@...r.kernel.org>,
        "moderated list:ARM/Allwinner sunXi SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] cpufreq: sun50i: Fix CPU speed bin detection

On 03-11-19, 16:59, Maxime Ripard wrote:
> On Fri, Nov 01, 2019 at 05:41:51PM +0100, Ondrej Jirman wrote:
> > I have observed failures to boot on Orange Pi 3, because this driver
> > determined that my SoC is from the normal bin, but my SoC only works
> > reliably with the OPP values for the slowest bin.
> >
> > By querying H6 owners, it was found that e-fuse values found in the wild
> > are in the range of 1-3, value of 7 was not reported, yet. From this and
> > from unused defines in BSP code, it can be assumed that meaning of efuse
> > values on H6 actually is:
> >
> > - 1 = slowest bin
> > - 2 = normal bin
> > - 3 = fastest bin
> >
> > Vendor code actually treats 0 and 2 as invalid efuse values, but later
> > treats all invalid values as a normal bin. This looks like a mistake in
> > bin detection code, that was plastered over by a hack in cpufreq code,
> > so let's not repeat it here. It probably only works because there are no
> > SoCs in the wild with efuse value of 0, and fast bin SoCs are made to
> > use normal bin OPP tables, which is also safe.
> >
> > Let's play it safe and interpret 0 as the slowest bin, but fix detection
> > of other bins to match this research. More research will be done before
> > actual OPP tables are merged.
> >
> > Fixes: f328584f7bff ("cpufreq: Add sun50i nvmem based CPU scaling driver")
> > Signed-off-by: Ondrej Jirman <megous@...ous.com>
> 
> Acked-by: Maxime Ripard <mripard@...nel.org>

Applied. Thanks.

-- 
viresh