linux-kernel - Re: [PATCH] thermal/idle_inject: Support 100% idle injection

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Message-ID: <2608bee3-7571-dc82-caa9-0aab2735512e@linaro.org>
Date:   Wed, 18 Jan 2023 09:18:47 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        rafael@...nel.org
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        rui.zhang@...el.com
Subject: Re: [PATCH] thermal/idle_inject: Support 100% idle injection

On 17/01/2023 19:22, Srinivas Pandruvada wrote:
> The users of idle injection framework allow 100% idle injection. For
> example: thermal/cpuidle_cooling.c driver. When the ratio set to 100%,
> the runtime_duration becomes zero.
> 
> In the function idle_inject_set_duration() in idle injection framework
> run_duration_us == 0 is silently ignored, without any error (it is a
> void function). So, the caller will assume that everything is fine and
> 100% idle is effective. But in reality the idle inject will be whatever
> set before.
> 
> There are two options:
> - The caller change their max state to 99% instead of 100% and
> document that 100% is not supported by idle inject framework
> - Support 100% idle support in idle inject framework
> 
> Since there are other protections via RT throttling, this framework can
> allow 100% idle. The RT throttling will be activated at 95% idle by
> default. The caller disabling RT throttling and injecting 100% idle,
> should be aware that CPU can't be used at all.
> 
> The idle inject timer is started for (run_duration_us + idle_duration_us)
> duration. Hence replace (run_duration_us && idle_duration_us) with
> (run_duration_us + idle_duration_us) in the function
> idle_inject_set_duration(). Also check for !(run_duration_us +
> idle_duration_us) to return -EINVAL in the function idle_inject_start().
> 
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
> ---

Acked-by: Daniel Lezcano <daniel.lezcano@...aro.org>

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