linux-kernel - Re: [PATCH] ARM: dts: imx6sx-sdb: Remove cpufreq OPP override

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Message-ID: <CAOMZO5CKUsEr1yf5RrsPLipNtLC_6sK0dPjT2M-eN-uo8hEbrQ@mail.gmail.com>
Date:   Tue, 25 Apr 2017 14:02:51 -0300
From:   Fabio Estevam <festevam@...il.com>
To:     Leonard Crestez <leonard.crestez@....com>
Cc:     Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <kernel@...gutronix.de>,
        Peter Chen <Peter.Chen@....com>,
        Anson Huang <Anson.Huang@....com>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Fabio Estevam <fabio.estevam@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Christoph Fritz <chf.fritz@...glemail.com>,
        Marek Vasut <marex@...x.de>
Subject: Re: [PATCH] ARM: dts: imx6sx-sdb: Remove cpufreq OPP override

On Tue, Apr 25, 2017 at 2:02 PM, Fabio Estevam <festevam@...il.com> wrote:
> Hi Leonard,
>
> On Tue, Apr 25, 2017 at 1:57 PM, Leonard Crestez
> <leonard.crestez@....com> wrote:
>> The board file for imx6sx-dbg overrides cpufreq operating points to use
>> higher voltages. This is done because the board has a shared rail for
>> VDD_ARM_IN and VDD_SOC_IN and when using LDO bypass the shared voltage
>> needs to be a value suitable for both ARM and SOC.
>>
>> This was introduced in:
>>
>> commit 54183bd7f766 ("ARM: imx6sx-sdb: add revb board and make it default")
>>
>> This only only applies to LDO bypass mode, a feature not present in
>> upstream. When LDOs are enabled the effect is to use higher voltages than
>> necesarry for no good reason.
>>
>> Setting these higher voltages can make some boards fail to boot with ugly
>> semi-random crashes, reminiscent of memory corruption. These failures
>> happen the first time the lowest idle state is used. Remove the OPP
>> override in order to fix those crashes.
>>
>> Signed-off-by: Leonard Crestez <leonard.crestez@....com>
>>
>> ---
>> It's not clear exactly why the crashes happen. Perhaps waking up from idle
>> draws more power than is available? Removing this override is a correct
>> change anyway so maybe there is no need to investigate deeper.
>
> Marek just sent a similar one a few minutes ago:
> http://lists.infradead.org/pipermail/linux-arm-kernel/2017-April/503230.html

Forgot to add Marek.