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From: Jingoo Han <jg1.han@samsung.com>
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In-reply-to: <1383022663-22315-1-git-send-email-sachin.kamat@linaro.org>
Subject: Re: [PATCH 1/1] pwm: samsung: Fix kernel warning while unexporting a
 channel
Date: Tue, 29 Oct 2013 14:04:48 +0900
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To: 'Sachin Kamat' <sachin.kamat@linaro.org>, 'Thierry Reding' <thierry.reding@gmail.com>
Cc: linux-pwm@vger.kernel.org, linux-samsung-soc@vger.kernel.org, 'Tomasz Figa' <tomasz.figa@gmail.com>, 'Jingoo Han' <jg1.han@samsung.com>

On Tuesday, October 29, 2013 1:58 PM, Sachin Kamat wrote:
> 
> PWM channel data was set to NULL before freeing it. This caused the
> following kernel warning while unexporting the channel. Set the channel
> data to NULL after freeing it.
> 
> [   70.495000] WARNING: CPU: 0 PID: 1 at drivers/base/devres.c:805 pwm_put+0x48/0x80()
> [   70.505000] Modules linked in:
> [   70.505000] CPU: 0 PID: 1 Comm: sh Not tainted 3.12.0-rc6-next-20131024-00012-gd4aec04-dirty #58
> [   70.515000] [<c0014ddc>] (unwind_backtrace+0x0/0xf4) from [<c0011784>] (show_stack+0x10/0x14)
> [   70.525000] [<c0011784>] (show_stack+0x10/0x14) from [<c03a3cbc>] (dump_stack+0x7c/0xb0)
> [   70.530000] [<c03a3cbc>] (dump_stack+0x7c/0xb0) from [<c001de68>] (warn_slowpath_common+0x6c/0x88)
> [   70.540000] [<c001de68>] (warn_slowpath_common+0x6c/0x88) from [<c001df20>]
> (warn_slowpath_null+0x1c/0x24)
> [   70.550000] [<c001df20>] (warn_slowpath_null+0x1c/0x24) from [<c01d1af8>] (pwm_put+0x48/0x80)
> [   70.560000] [<c01d1af8>] (pwm_put+0x48/0x80) from [<c01d21c8>] (pwm_unexport_store+0x94/0xac)
> [   70.565000] [<c01d21c8>] (pwm_unexport_store+0x94/0xac) from [<c010991c>]
> (sysfs_write_file+0x148/0x1d8)
> [   70.575000] [<c010991c>] (sysfs_write_file+0x148/0x1d8) from [<c00b2a80>] (vfs_write+0xb4/0x1a0)
> [   70.585000] [<c00b2a80>] (vfs_write+0xb4/0x1a0) from [<c00b3068>] (SyS_write+0x3c/0x78)
> [   70.595000] [<c00b3068>] (SyS_write+0x3c/0x78) from [<c000e2e0>] (ret_fast_syscall+0x0/0x30)
> 
> Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>

Reviewed-by: Jingoo Han <jg1.han@samsung.com>

Best regards,
Jingoo Han

> ---
>  drivers/pwm/pwm-samsung.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/pwm/pwm-samsung.c b/drivers/pwm/pwm-samsung.c
> index b2c54c8..6d23eb3 100644
> --- a/drivers/pwm/pwm-samsung.c
> +++ b/drivers/pwm/pwm-samsung.c
> @@ -226,8 +226,8 @@ static int pwm_samsung_request(struct pwm_chip *chip, struct pwm_device *pwm)
> 
>  static void pwm_samsung_free(struct pwm_chip *chip, struct pwm_device *pwm)
>  {
> -	pwm_set_chip_data(pwm, NULL);
>  	devm_kfree(chip->dev, pwm_get_chip_data(pwm));
> +	pwm_set_chip_data(pwm, NULL);
>  }
> 
>  static int pwm_samsung_enable(struct pwm_chip *chip, struct pwm_device *pwm)
> --
> 1.7.9.5