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

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Date:   Sun, 3 Nov 2019 16:59:01 +0100
From:   Maxime Ripard <mripard@...nel.org>
To:     Ondrej Jirman <megous@...ous.com>
Cc:     linux-sunxi@...glegroups.com, Yangtao Li <tiny.windzz@...il.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        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 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>

Maxime

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