linux-kernel - Re: [PATCH V2 2/6] Thermal: make sure cpufreq cooling register after cpufreq driver

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Date:	Mon, 29 Oct 2012 17:12:35 +0530
From:	Amit Kachhap <amit.kachhap@...aro.org>
To:	"hongbo.zhang" <hongbo.zhang@...aro.org>
Cc:	linaro-dev@...ts.linaro.org, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org, STEricsson_nomadik_linux@...t.st.com,
	kernel@...oocommunity.org, linaro-kernel@...ts.linaro.org,
	"hongbo.zhang" <hongbo.zhang@...aro.com>, patches@...aro.org
Subject: Re: [PATCH V2 2/6] Thermal: make sure cpufreq cooling register after
 cpufreq driver

On 24 October 2012 17:28, hongbo.zhang <hongbo.zhang@...aro.org> wrote:
> From: "hongbo.zhang" <hongbo.zhang@...aro.com>
>
> The cpufreq works as a cooling device, so the cooling layer should check if the
> cpufreq driver is initialized or not.
>
> Signed-off-by: hongbo.zhang <hongbo.zhang@...aro.com>
> ---
>  drivers/thermal/cpu_cooling.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c
> index b6b4c2a..7519a0b 100644
> --- a/drivers/thermal/cpu_cooling.c
> +++ b/drivers/thermal/cpu_cooling.c
> @@ -354,6 +354,10 @@ struct thermal_cooling_device *cpufreq_cooling_register(
>         int ret = 0, i;
>         struct cpufreq_policy policy;
>
> +       /* make sure cpufreq driver has been initialized */
> +       if (!cpufreq_frequency_get_table(cpumask_any(clip_cpus)))
> +               return ERR_PTR(-EPROBE_DEFER);
> +
Hi Hongbo,

I am not against this change but this might cause unnecessary delay in
probe thread. I also thought about it but have not put this
restriction. Actually you can put a check in platform_bind for this
condition and defer the binding till the time actual throttling
starts. So basically only after throttling cpufreq_table is needed.
(See my implementation exynos_thermal.c).

Thanks,
Amit Daniel
>         list_for_each_entry(cpufreq_dev, &cooling_cpufreq_list, node)
>                 cpufreq_dev_count++;
>
> --
> 1.7.11.3
>
>
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> linaro-dev@...ts.linaro.org
> http://lists.linaro.org/mailman/listinfo/linaro-dev
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