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From:   Jon Hunter <jonathanh@nvidia.com>
Subject: Re: [PATCH v2] cpuidle: tegra: Correctly handle result of
 arm_cpuidle_simple_enter()
To:     Dmitry Osipenko <digetx@gmail.com>,
        Thierry Reding <thierry.reding@gmail.com>,
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On 02/07/2020 01:13, Dmitry Osipenko wrote:
> The enter() callback of CPUIDLE drivers returns index of the entered idle
> state on success or a negative value on failure. The negative value could
> any negative value, i.e. it doesn't necessarily needs to be a error code.
> That's because CPUIDLE core only cares about the fact of failure and not
> about the reason of the enter() failure.
> 
> Like every other enter() callback, the arm_cpuidle_simple_enter() returns
> the entered idle-index on success. Unlike some of other drivers, it never
> fails. It happened that TEGRA_C1=index=err=0 in the code of cpuidle-tegra
> driver, and thus, there is no problem for the cpuidle-tegra driver created
> by the typo in the code which assumes that the arm_cpuidle_simple_enter()
> returns a error code.
> 
> The arm_cpuidle_simple_enter() also may return a -ENODEV error if CPU_IDLE
> is disabled in a kernel's config, but all CPUIDLE drivers are disabled if
> CPU_IDLE is disabled, including the cpuidle-tegra driver. So we can't ever
> see the error code from arm_cpuidle_simple_enter() today.
> 
> Of course the code may get some changes in the future and then the typo
> may transform into a real bug, so let's correct the typo in the code by
> making tegra_cpuidle_enter() to directly return the index returned by the
> arm_cpuidle_simple_enter().

Are you suggesting that arm_cpuidle_simple_enter() could be updated to
actually return an error? Sorry it is not clear to me what you are implying.

Cheers
Jon

-- 
nvpublic