linux-kernel - Re: [PATCH 1/3] thermal: exynos: Fix NULL pointer exception during kernel booting

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Message-id: <20150216160633.29eac148@amdc2363>
Date:	Mon, 16 Feb 2015 16:06:33 +0100
From:	Lukasz Majewski <l.majewski@...sung.com>
To:	Chanwoo Choi <cw00.choi@...sung.com>
Cc:	rui.zhang@...el.com, edubezval@...il.com, kgene@...nel.org,
	b.zolnierkie@...sung.com, kyungmin.park@...sung.com,
	amit.daniel@...sung.com, a.kesavan@...sung.com,
	inki.dae@...sung.com, linux-pm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] thermal: exynos: Fix NULL pointer exception during
 kernel booting

Hi Chanwoo,

> This patch fixes the NULL pointer exception during kernel booting.
> The thermal_zone _of_sensor_register() registers a sensor to DT
> thermal zone and then read the current temperature by '.get_temp'
> callback. The callback function of exynos thermal driver is
> exynos_get_temp() which must need the 'pdata' instance of exynos_tmu
> _platform_data structure.
> - exynos_get_temp() -> code_to_temp() -> Must need the 'pdata'
> instance
> 
> But, exynos thermal driver is executed before getting the 'pdata'
> instance. To avoid the kernel panic, have to get the platform data by
> executing the exynos_map_dt_data() before calling
> thermal_zone_of_sensor_register() .

I've already prepared patch for this (unfortunately it isn't yet
applied to mainline):

"[PATCH] thermal: exynos: fix: Check if data->tmu_read callback is
present before read"

http://www.spinics.net/lists/linux-samsung-soc/msg42245.html

Does applying this patch help?

BTW: How can I reproduce this error? Could you point me the SHA1 and
repository?

> 
> - kernel panic log
> [ 4211.324346] PC is at 0x0
> [ 4211.326867] LR is at exynos_get_temp+0x3c/0xe4
> [ 4211.331289] pc : [<0000000000000000>] lr : [<ffffffc0004df460>]
> [snip]
> [ 4211.940625] [<          (null)>]           (null)
> [ 4211.945315] [<ffffffc0004de6d8>] of_thermal_get_temp+0x1c/0x30
> [ 4211.951132] [<ffffffc0004db86c>] thermal_zone_get_temp+0x48/0x7c
> [ 4211.957118] [<ffffffc0004dd278>]
> thermal_zone_device_update+0x20/0x110 [ 4211.963627]
> [<ffffffc0004de9c8>] of_thermal_set_mode+0x44/0x68 [ 4211.969443]
> [<ffffffc0004decb8>] thermal_zone_of_sensor_register+0x15c/0x1d8
> [ 4211.976475] [<ffffffc0004dfbe4>] exynos_tmu_probe+0x6c/0x814
> [ 4211.982120] [<ffffffc0003ef808>] platform_drv_probe+0x48/0xb8
> [ 4211.987846] [<ffffffc0003edb28>] driver_probe_device+0x8c/0x244
> [ 4211.993747] [<ffffffc0003eddcc>] __driver_attach+0x98/0xa0
> [ 4211.999216] [<ffffffc0003ebea0>] bus_for_each_dev+0x54/0x98
> [ 4212.004771] [<ffffffc0003ed66c>] driver_attach+0x1c/0x28
> [ 4212.010066] [<ffffffc0003ed2e8>] bus_add_driver+0x150/0x208
> [ 4212.015622] [<ffffffc0003ee6a4>] driver_register+0x5c/0x11c
> [ 4212.021178] [<ffffffc0003ef73c>]
> __platform_driver_register+0x5c/0x68 [ 4212.027600]
> [<ffffffc000b64eb8>] exynos_tmu_driver_init+0x14/0x20 [ 4212.033678]
> [<ffffffc0000828d4>] do_one_initcall+0x88/0x1a0 [ 4212.039235]
> [<ffffffc000b34b34>] kernel_init_freeable+0x1bc/0x260 [ 4212.045311]
> [<ffffffc0007e9fd4>] kernel_init+0xc/0xd8
> 
> Cc: Zhang Rui <rui.zhang@...el.com>
> Cc: Eduardo Valentin <edubezval@...il.com>
> Signed-off-by: Chanwoo Choi <cw00.choi@...sung.com>
> ---
>  drivers/thermal/samsung/exynos_tmu.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/thermal/samsung/exynos_tmu.c
> b/drivers/thermal/samsung/exynos_tmu.c index fbeedc0..b8846f1 100644
> --- a/drivers/thermal/samsung/exynos_tmu.c
> +++ b/drivers/thermal/samsung/exynos_tmu.c
> @@ -1147,17 +1147,17 @@ static int exynos_tmu_probe(struct
> platform_device *pdev) platform_set_drvdata(pdev, data);
>  	mutex_init(&data->lock);
>  
> +	ret = exynos_map_dt_data(pdev);
> +	if (ret)
> +		return ret;
> +	pdata = data->pdata;
> +
>  	data->tzd = thermal_zone_of_sensor_register(&pdev->dev, 0,
> data, &exynos_sensor_ops);
>  	if (IS_ERR(data->tzd)) {
>  		pr_err("thermal: tz: %p ERROR\n", data->tzd);
>  		return PTR_ERR(data->tzd);
>  	}
> -	ret = exynos_map_dt_data(pdev);
> -	if (ret)
> -		goto err_sensor;
> -
> -	pdata = data->pdata;
>  
>  	INIT_WORK(&data->irq_work, exynos_tmu_work);
>  



-- 
Best regards,

Lukasz Majewski

Samsung R&D Institute Poland (SRPOL) | Linux Platform Group
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