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Subject: Re: [PATCH] PM / devfreq: try_then_request_governor should not
 return NULL
To:     Rob Clark <robdclark@gmail.com>, linux-arm-msm@vger.kernel.org
Cc:     Rob Clark <robdclark@chromium.org>,
        MyungJoo Ham <myungjoo.ham@samsung.com>,
        Kyungmin Park <kyungmin.park@samsung.com>,
        linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org
From:   Chanwoo Choi <cw00.choi@samsung.com>
Organization: Samsung Electronics
Message-ID: <9c63ac15-9917-7adc-3ef8-3e44060797bd@samsung.com>
Date:   Fri, 24 May 2019 16:15:16 +0900
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References: <CGME20190523215902epcas5p40e3aca0efb342c8d778529fef416c3fd@epcas5p4.samsung.com>
        <20190523215853.16622-1-robdclark@gmail.com>
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Hi,

This issue[1] is already fixed on latest linux.git 
You can check it. Thanks.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b53b0128052ffd687797d5f4deeb76327e7b5711

Regards,
Chanwoo Choi


On 19. 5. 24. 오전 6:58, Rob Clark wrote:
> From: Rob Clark <robdclark@chromium.org>
> 
> The two spots it is called expect either an IS_ERR() or a valid pointer,
> but not NULL.
> 
> Fixes this crash that I came across:
> 
>    Unable to handle kernel NULL pointer dereference at virtual address 0000000000000030
>    Mem abort info:
>      ESR = 0x96000005
>      Exception class = DABT (current EL), IL = 32 bits
>      SET = 0, FnV = 0
>      EA = 0, S1PTW = 0
>    Data abort info:
>      ISV = 0, ISS = 0x00000005
>      CM = 0, WnR = 0
>    [0000000000000030] user address but active_mm is swapper
>    Internal error: Oops: 96000005 [#1] PREEMPT SMP
>    Modules linked in:
>    Process kworker/2:1 (pid: 212, stack limit = 0x(____ptrval____))
>    CPU: 2 PID: 212 Comm: kworker/2:1 Not tainted 5.1.0-43338-g460e6984675c-dirty #54
>    Hardware name: Google Cheza (rev3+) (DT)
>    Workqueue: events deferred_probe_work_func
>    pstate: 00c00009 (nzcv daif +PAN +UAO)
>    pc : devfreq_add_device+0x2e4/0x410
>    lr : devfreq_add_device+0x2d4/0x410
>    sp : ffffff8013d93740
>    x29: ffffff8013d93790 x28: ffffffc0f54f8670
>    x27: 0000000000000001 x26: 0000000000000007
>    x25: ffffff80124abfd8 x24: 0000000000000000
>    x23: ffffffc0fabc4048 x22: ffffffc0fabc4388
>    x21: ffffffc0fabc4010 x20: ffffffc0fa243010
>    x19: ffffffc0fabc4000 x18: 0000000091c3d373
>    x17: 0000000000000400 x16: 000000000000001a
>    x15: 000000019e06d400 x14: 0000000000000001
>    x13: 0000000000000000 x12: 00000000000006b6
>    x11: 0000000000000000 x10: 0000000000000000
>    x9 : ffffffc0fa18ba00 x8 : 0000000000000000
>    x7 : 0000000000000000 x6 : ffffff80127a3d9a
>    x5 : ffffff8013d93550 x4 : 0000000000000000
>    x3 : 0000000000000000 x2 : 0000000000000000
>    x1 : 00000000000000fe x0 : 0000000000000000
>    Call trace:
>     devfreq_add_device+0x2e4/0x410
>     devm_devfreq_add_device+0x64/0xac
>     msm_gpu_init+0x320/0x5c0
>     adreno_gpu_init+0x21c/0x274
>     a6xx_gpu_init+0x68/0xf4
>     adreno_bind+0x158/0x284
>     component_bind_all+0x110/0x204
>     msm_drm_bind+0x118/0x5b8
>     try_to_bring_up_master+0x15c/0x19c
>     component_master_add_with_match+0xb4/0xec
>     msm_pdev_probe+0x1f0/0x27c
>     platform_drv_probe+0x90/0xb0
>     really_probe+0x120/0x298
>     driver_probe_device+0x64/0xfc
>     __device_attach_driver+0x8c/0xa4
>     bus_for_each_drv+0x88/0xd0
>     __device_attach+0xac/0x134
>     device_initial_probe+0x20/0x2c
>     bus_probe_device+0x34/0x90
>     deferred_probe_work_func+0x74/0xac
>     process_one_work+0x210/0x428
>     worker_thread+0x278/0x3e4
>     kthread+0x120/0x130
>     ret_from_fork+0x10/0x18
>    Code: aa0003f8 b13ffc1f 54000762 f901c278 (f9401b08)
>    ---[ end trace a6ecc18ce5894375 ]---
>    Kernel panic - not syncing: Fatal exception
> 
> Signed-off-by: Rob Clark <robdclark@chromium.org>
> ---
>  drivers/devfreq/devfreq.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 0ae3de76833b..d29f66f0e52a 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -254,7 +254,7 @@ static struct devfreq_governor *try_then_request_governor(const char *name)
>  		/* Restore previous state before return */
>  		mutex_lock(&devfreq_list_lock);
>  		if (err)
> -			return NULL;
> +			return ERR_PTR(err);
>  
>  		governor = find_devfreq_governor(name);
>  	}
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics