linux-kernel - Re: [PATCH -next] PM / OPP: Fix crash seen if CPU clock has no voltage regulator

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Message-ID: <20160216004639.GF6334@vireshk-i7>
Date:	Tue, 16 Feb 2016 06:16:39 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] PM / OPP: Fix crash seen if CPU clock has no
 voltage regulator

On 15-02-16, 11:34, Guenter Roeck wrote:
> omap3 overo boots crash with
> 
> Unable to handle kernel NULL pointer dereference at virtual address 00000030
> pgd = c0204000
> [00000030] *pgd=00000000
> Internal error: Oops: 17 [#1] SMP ARM
> ...
> [] (regulator_set_voltage) from [] (_set_opp_voltage+0x34/0x90)
> [] (_set_opp_voltage) from [] (dev_pm_opp_set_rate+0x19c/0x288)
> [] (dev_pm_opp_set_rate) from [] (__cpufreq_driver_target+0x17c/0x29c)
> [] (__cpufreq_driver_target) from [] (dbs_check_cpu+0x19c/0x1e4)
> [] (dbs_check_cpu) from [] (cpufreq_governor_dbs+0x308/0x5c4)
> [] (cpufreq_governor_dbs) from [] (__cpufreq_governor+0x20c/0x24c)
> [] (__cpufreq_governor) from [] (cpufreq_init_policy+0x60/0x8c)
> [] (cpufreq_init_policy) from [] (cpufreq_online+0x2cc/0x6d8)
> [] (cpufreq_online) from [] (subsys_interface_register+0x80/0xc4)
> [] (subsys_interface_register) from [] (cpufreq_register_driver+0x144/0x1a0)
> [] (cpufreq_register_driver) from [] (dt_cpufreq_probe+0x64/0xe8)
> [] (dt_cpufreq_probe) from [] (platform_drv_probe+0x50/0xb0)
> [] (platform_drv_probe) from [] (driver_probe_device+0x1f4/0x2b0)
> ...
> 
> Analysis shows that regulator==NULL in regulator_set_voltage().
> Code around _set_opp_voltage() suggests that having no voltage regulator
> attached to a CPU clock is valid, so do not attempt to set a voltage
> in that case.
> 
> Fixes: 6a0712f6f199e ("PM / OPP: Add dev_pm_opp_set_rate()"
> Cc: Viresh Kumar <viresh.kumar@...aro.org>
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
> ---
>  drivers/base/power/opp/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Sorry about that, a separate fix for the same is pushed by Rafael in
pm/linux-next now.

-- 
viresh