linux-kernel - Re: [PATCH 5/8] thermal:cpu cooling:tegra: Provide deferred probing for tegra driver

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Date:	Fri, 14 Nov 2014 12:47:33 +0200
From:	Mikko Perttunen <mikko.perttunen@...si.fi>
To:	Lukasz Majewski <l.majewski@...sung.com>,
	Eduardo Valentin <edubezval@...il.com>,
	Zhang Rui <rui.zhang@...el.com>
CC:	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>,
	Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Vincenzo Frascino <vincenzo.frascino@...com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Lukasz Majewski <l.majewski@...ess.pl>,
	Nobuhiro Iwamatsu <iwamatsu@...auri.org>,
	Mikko Perttunen <mperttunen@...dia.com>,
	Stephen Warren <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Alexandre Courbot <gnurou@...il.com>,
	linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/8] thermal:cpu cooling:tegra: Provide deferred probing
 for tegra driver

Tested-by: Mikko Perttunen <mikko.perttunen@...si.fi>

One potential issue I can see is that if the cpufreq driver fails to 
probe then you'll never get the thermal driver either. For example, 
Tegra124 currently has no cpufreq driver, so if CONFIG_CPU_THERMAL was 
enabled, then the soctherm driver would never be able to probe. But I 
don't really have a solution for this either.

Cheers,
Mikko

On 11/13/2014 07:02 PM, Lukasz Majewski wrote:
> When CPU freq is used as a thermal zone cooling device, one needs to wait
> until cpufreq subsystem is properly initialized.
>
> This code is similar to the one already available in imx_thermal.c file.
>
> Signed-off-by: Lukasz Majewski <l.majewski@...sung.com>
> ---
>   drivers/thermal/tegra_soctherm.c | 7 +++++++
>   1 file changed, 7 insertions(+)
>
> diff --git a/drivers/thermal/tegra_soctherm.c b/drivers/thermal/tegra_soctherm.c
> index 70f7e9e..9c5aaa4 100644
> --- a/drivers/thermal/tegra_soctherm.c
> +++ b/drivers/thermal/tegra_soctherm.c
> @@ -26,6 +26,7 @@
>   #include <linux/platform_device.h>
>   #include <linux/reset.h>
>   #include <linux/thermal.h>
> +#include <linux/cpufreq.h>
>
>   #include <soc/tegra/fuse.h>
>
> @@ -346,6 +347,12 @@ static int tegra_soctherm_probe(struct platform_device *pdev)
>
>   	const struct tegra_tsensor *tsensors = t124_tsensors;
>
> +#ifdef CONFIG_CPU_THERMAL
> +	if (!cpufreq_get_current_driver()) {
> +		dev_dbg(&pdev->dev, "no cpufreq driver!");
> +		return -EPROBE_DEFER;
> +	}
> +#endif
>   	tegra = devm_kzalloc(&pdev->dev, sizeof(*tegra), GFP_KERNEL);
>   	if (!tegra)
>   		return -ENOMEM;
>

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