[PATCH v2] media: platform: fix a kernel warning on clk control
Jae Hyun Yoo
jae.hyun.yoo at linux.intel.com
Sat Apr 13 02:26:28 AEST 2019
On 4/12/2019 7:33 AM, Eddie James wrote:
>
> On 4/12/19 7:17 AM, Herrenschmidt, Benjamin wrote:
>> On Fri, 2019-04-12 at 13:00 +0200, Hans Verkuil wrote:
>>> Eddie, can you review this?
>
>
> Yes, this looks good.
>
> Thanks,
>
> Reviewed-by: Eddie James <eajames at linux.ibm.com>
Thanks Eddie!
I'll submit a new patch on top of your upstreaming patch. It would be
better to match the merge order with our downstream tree.
Regards,
Jae
>>>
>>> Jae Hyun Yoo, for future reference: please add the driver name in the
>>> subject.
>>> I.e. something like this: [PATCH v2] media: aspeed: fix a kernel
>>> warning on clk control
>>>
>>> That helps maintainers figuring out who should look at which patch.
>> test_bit/clear_bit/set_bit are atomic. The way they are used here is
>> either a waste of cycles (there's already a lock) or racy. Not too sure
>
>
> Yes, it's conceivable that this could be done locklessly, but I'm fine
> with being cautious. I asked Jae to use the bit functions and flag for
> code cleanliness instead of an additional bool... are the additional
> cycles that bad here?
>
>
>> :)
>>
>> Cheers,
>> Ben.
>>
>>> Regards,
>>>
>>> Hans
>>>
>>> On 3/29/19 10:27 PM, Jae Hyun Yoo wrote:
>>>> video_on and video_off functions in the Aspeed video engine driver
>>>> are
>>>> being called from multiple contexts without any protection so video
>>>> clocks
>>>> can be disabled twice and eventually it causes a kernel warning
>>>> with stack
>>>> dump printing out like below:
>>>>
>>>> [ 120.034729] WARNING: CPU: 0 PID: 1334 at drivers/clk/clk.c:684
>>>> clk_core_unprepare+0x13c/0x170
>>>> [ 120.043252] eclk-gate already unprepared
>>>> [ 120.047283] CPU: 0 PID: 1334 Comm: obmc-ikvm Tainted:
>>>> G W 5.0.3-b94b74e8b52db91fe4e99e0bb481ec8bf2b5b47c
>>>> #1
>>>> [ 120.058417] Hardware name: Generic DT based system
>>>> [ 120.063219] Backtrace:
>>>> [ 120.065787] [<80107cdc>] (dump_backtrace) from [<80107f10>]
>>>> (show_stack+0x20/0x24)
>>>> [ 120.073371] r7:803a4ff0 r6:00000009 r5:00000000 r4:96197e1c
>>>> [ 120.079152] [<80107ef0>] (show_stack) from [<8068f7d8>]
>>>> (dump_stack+0x20/0x28)
>>>> [ 120.086479] [<8068f7b8>] (dump_stack) from [<8011604c>]
>>>> (__warn.part.3+0xb4/0xdc)
>>>> [ 120.094068] [<80115f98>] (__warn.part.3) from [<801160e0>]
>>>> (warn_slowpath_fmt+0x6c/0x90)
>>>> [ 120.102164] r6:000002ac r5:8080c0b8 r4:80a07008
>>>> [ 120.106893] [<80116078>] (warn_slowpath_fmt) from [<803a4ff0>]
>>>> (clk_core_unprepare+0x13c/0x170)
>>>> [ 120.115686] r3:8080cf8c r2:8080c17c
>>>> [ 120.119276] r7:97d68e58 r6:9df23200 r5:9668c260 r4:96459260
>>>> [ 120.125046] [<803a4eb4>] (clk_core_unprepare) from [<803a707c>]
>>>> (clk_unprepare+0x34/0x3c)
>>>> [ 120.133226] r5:9668c260 r4:96459260
>>>> [ 120.136932] [<803a7048>] (clk_unprepare) from [<804f34bc>]
>>>> (aspeed_video_off+0x44/0x48)
>>>> [ 120.145031] r5:9668c260 r4:9668cbc0
>>>> [ 120.148647] [<804f3478>] (aspeed_video_off) from [<804f3fd0>]
>>>> (aspeed_video_release+0x94/0x118)
>>>> [ 120.157435] r5:966a0cb8 r4:966a0800
>>>> [ 120.161049] [<804f3f3c>] (aspeed_video_release) from
>>>> [<804d2c58>] (v4l2_release+0xd4/0xe8)
>>>> [ 120.169404] r7:97d68e58 r6:9d087810 r5:9df23200 r4:966a0b20
>>>> [ 120.175168] [<804d2b84>] (v4l2_release) from [<80236224>]
>>>> (__fput+0x98/0x1c4)
>>>> [ 120.182316] r5:96698e78 r4:9df23200
>>>> [ 120.185994] [<8023618c>] (__fput) from [<802363b8>]
>>>> (____fput+0x18/0x1c)
>>>> [ 120.192712] r9:80a0700c r8:801011e4 r7:00000000 r6:80a64bbc
>>>> r5:961dd560 r4:961dd89c
>>>> [ 120.200562] [<802363a0>] (____fput) from [<80131c08>]
>>>> (task_work_run+0x7c/0xa4)
>>>> [ 120.207994] [<80131b8c>] (task_work_run) from [<80106884>]
>>>> (do_work_pending+0x4a8/0x578)
>>>> [ 120.216163] r7:801011e4 r6:80a07008 r5:96197fb0 r4:ffffe000
>>>> [ 120.221856] [<801063dc>] (do_work_pending) from [<8010106c>]
>>>> (slow_work_pending+0xc/0x20)
>>>> [ 120.230116] Exception stack(0x96197fb0 to 0x96197ff8)
>>>> [ 120.235254] 7fa0: 00000000
>>>> 76ccf094 00000000 00000000
>>>> [ 120.243438] 7fc0: 00000008 00a11978 7eab3c30 00000006 00000000
>>>> 00000000 475b0fa4 00000000
>>>> [ 120.251692] 7fe0: 00000002 7eab3a40 00000000 47720e38 80000010
>>>> 00000008
>>>> [ 120.258396] r10:00000000 r9:96196000 r8:801011e4 r7:00000006
>>>> r6:7eab3c30 r5:00a11978
>>>> [ 120.266291] r4:00000008
>>>>
>>>> To prevent this issue, this commit adds spinlock protection and
>>>> clock
>>>> status checking logic into the Aspeed video engine driver.
>>>>
>>>> Fixes: d2b4387f3bdf ("media: platform: Add Aspeed Video Engine
>>>> driver")
>>>> Signed-off-by: Jae Hyun Yoo<jae.hyun.yoo at linux.intel.com>
>>>> Cc: Eddie James<eajames at linux.ibm.com>
>>>> Cc: Mauro Carvalho Chehab<mchehab at kernel.org>
>>>> Cc: Joel Stanley<joel at jms.id.au>
>>>> Cc: Andrew Jeffery<andrew at aj.id.au>
>>>> ---
>>>> drivers/media/platform/aspeed-video.c | 32
>>>> ++++++++++++++++++++++++---
>>>> 1 file changed, 29 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/media/platform/aspeed-video.c
>>>> b/drivers/media/platform/aspeed-video.c
>>>> index 692e08ef38c0..744d22ecc620 100644
>>>> --- a/drivers/media/platform/aspeed-video.c
>>>> +++ b/drivers/media/platform/aspeed-video.c
>>>> @@ -188,6 +188,7 @@ enum {
>>>> VIDEO_STREAMING,
>>>> VIDEO_FRAME_INPRG,
>>>> VIDEO_STOPPED,
>>>> + VIDEO_CLOCKS_ON,
>>>> };
>>>> struct aspeed_video_addr {
>>>> @@ -495,20 +496,30 @@ static void aspeed_video_reset(struct
>>>> aspeed_video *video)
>>>> static void aspeed_video_off(struct aspeed_video *video)
>>>> {
>>>> + if (!test_bit(VIDEO_CLOCKS_ON, &video->flags))
>>>> + return;
>>>> +
>>>> aspeed_video_reset(video);
>>>> /* Turn off the relevant clocks */
>>>> clk_disable_unprepare(video->vclk);
>>>> clk_disable_unprepare(video->eclk);
>>>> +
>>>> + clear_bit(VIDEO_CLOCKS_ON, &video->flags);
>>>> }
>>>> static void aspeed_video_on(struct aspeed_video *video)
>>>> {
>>>> + if (test_bit(VIDEO_CLOCKS_ON, &video->flags))
>>>> + return;
>>>> +
>>>> /* Turn on the relevant clocks */
>>>> clk_prepare_enable(video->eclk);
>>>> clk_prepare_enable(video->vclk);
>>>> aspeed_video_reset(video);
>>>> +
>>>> + set_bit(VIDEO_CLOCKS_ON, &video->flags);
>>>> }
>>>> static void aspeed_video_bufs_done(struct aspeed_video *video,
>>>> @@ -526,12 +537,14 @@ static void aspeed_video_bufs_done(struct
>>>> aspeed_video *video,
>>>> static void aspeed_video_irq_res_change(struct aspeed_video
>>>> *video)
>>>> {
>>>> + spin_lock(&video->lock);
>>>> dev_dbg(video->dev, "Resolution changed; resetting\n");
>>>> set_bit(VIDEO_RES_CHANGE, &video->flags);
>>>> clear_bit(VIDEO_FRAME_INPRG, &video->flags);
>>>> aspeed_video_off(video);
>>>> + spin_unlock(&video->lock);
>>>> aspeed_video_bufs_done(video, VB2_BUF_STATE_ERROR);
>>>> schedule_delayed_work(&video->res_work,
>>>> RESOLUTION_CHANGE_DELAY);
>>>> @@ -951,9 +964,13 @@ static void aspeed_video_init_regs(struct
>>>> aspeed_video *video)
>>>> static void aspeed_video_start(struct aspeed_video *video)
>>>> {
>>>> + unsigned long flags;
>>>> +
>>>> + spin_lock_irqsave(&video->lock, flags);
>>>> aspeed_video_on(video);
>>>> aspeed_video_init_regs(video);
>>>> + spin_unlock_irqrestore(&video->lock, flags);
>>>> /* Resolution set to 640x480 if no signal found */
>>>> aspeed_video_get_resolution(video);
>>>> @@ -969,6 +986,9 @@ static void aspeed_video_start(struct
>>>> aspeed_video *video)
>>>> static void aspeed_video_stop(struct aspeed_video *video)
>>>> {
>>>> + unsigned long flags;
>>>> +
>>>> + spin_lock_irqsave(&video->lock, flags);
>>>> set_bit(VIDEO_STOPPED, &video->flags);
>>>> cancel_delayed_work_sync(&video->res_work);
>>>> @@ -982,6 +1002,7 @@ static void aspeed_video_stop(struct
>>>> aspeed_video *video)
>>>> video->v4l2_input_status = V4L2_IN_ST_NO_SIGNAL;
>>>> video->flags = 0;
>>>> + spin_unlock_irqrestore(&video->lock, flags);
>>>> }
>>>> static int aspeed_video_querycap(struct file *file, void *fh,
>>>> @@ -1319,16 +1340,21 @@ static void
>>>> aspeed_video_resolution_work(struct work_struct *work)
>>>> struct delayed_work *dwork = to_delayed_work(work);
>>>> struct aspeed_video *video = container_of(dwork, struct
>>>> aspeed_video,
>>>> res_work);
>>>> - u32 input_status = video->v4l2_input_status;
>>>> + unsigned long flags;
>>>> + u32 input_status;
>>>> + spin_lock_irqsave(&video->lock, flags);
>>>> + input_status = video->v4l2_input_status;
>>>> aspeed_video_on(video);
>>>> /* Exit early in case no clients remain */
>>>> - if (test_bit(VIDEO_STOPPED, &video->flags))
>>>> + if (test_bit(VIDEO_STOPPED, &video->flags)) {
>>>> + spin_unlock_irqrestore(&video->lock, flags);
>>>> goto done;
>>>> + }
>>>> aspeed_video_init_regs(video);
>>>> -
>>>> + spin_unlock_irqrestore(&video->lock, flags);
>>>> aspeed_video_get_resolution(video);
>>>> if (video->detected_timings.width != video-
>>>>> active_timings.width ||
>
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