[PATCH v2] media: platform: fix a kernel warning on clk control
Herrenschmidt, Benjamin
benh at amazon.com
Fri Apr 12 22:18:47 AEST 2019
On Fri, 2019-04-12 at 13:00 +0200, Hans Verkuil wrote:
> Eddie, can you review this?
>
> 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
:)
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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