linux-kernel - Re: [PATCH 4/5] Thermal: make sure cpufreq cooling register after cpufreq driver

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Date:	Wed, 17 Oct 2012 20:06:11 +0530
From:	Viresh Kumar <viresh.kumar@...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 4/5] Thermal: make sure cpufreq cooling register after
 cpufreq driver

On 16 October 2012 17:14, 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 and wait until the cpufreq driver is initialized.

Idea is good.

> Signed-off-by: hongbo.zhang <hongbo.zhang@...aro.com>
> ---
>  drivers/thermal/cpu_cooling.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c
> index d196230..01aba58 100644
> --- a/drivers/thermal/cpu_cooling.c
> +++ b/drivers/thermal/cpu_cooling.c
> @@ -29,6 +29,7 @@
>  #include <linux/slab.h>
>  #include <linux/cpu.h>
>  #include <linux/cpu_cooling.h>
> +#include <linux/delay.h>

Would be better if we add them alphabetically. That makes there maintenance
easier. I know the list is already mismanaged. :)

If you can add another patch here to fix that, would be good.

>  /**
>   * struct cpufreq_cooling_device
> @@ -352,9 +353,18 @@ struct thermal_cooling_device *cpufreq_cooling_register(
>         struct cpufreq_cooling_device *cpufreq_dev = NULL;
>         unsigned int cpufreq_dev_count = 0, min = 0, max = 0;
>         char dev_name[THERMAL_NAME_LENGTH];
> -       int ret = 0, i;
> +       int ret = 0, to = 1000, i;
>         struct cpufreq_policy policy;
>
> +       /* make sure cpufreq driver is initialized */
> +       while (!cpufreq_frequency_get_table(0) && --to)
> +               mdelay(10);
> +
> +       if (!to) {
> +               pr_err("No cpufreq driver act as cooling device.\n");
> +               return ERR_PTR(-ENOSYS);
> +       }

I understand that you want cpufreq to be there before this thing, but
i didn't like the idea here. There should be something else like
returning -EPROBE_DEFER, so that driver can be pinged again.

--
viresh
--
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