On Thu, 2019-05-02 at 12:13 -0700, Jae Hyun Yoo wrote:
> Video engine clock control functions in the Aspeed video engine
> driver are being called from multiple context without any
> protection so video clocks can be double disabled and eventually
> it causes a kernel warning with stack dump printing out like below:
I already objected to the use of set_bit, clear_bit etc...
Either you are protected by a spinlock, in which case you don't need
them, use either the __ versions (non atomic) or just a bloody bool
flag which is a lot clearer and will generated better code. Or you
aren't protected in which case the code seems racy.
> [ 515.540498] ------------[ cut here ]------------
> [ 515.545174] WARNING: CPU: 0 PID: 1310 at drivers/clk/clk.c:684
> clk_core_unprepare+0x13c/0x170
> [ 515.553806] vclk-gate already unprepared
> [ 515.557841] CPU: 0 PID: 1310 Comm: obmc-ikvm Tainted:
> G W 5.0.6-df66fbc97853fbba90a0bfa44de32f3d5f7602b4 #1
> [ 515.568973] Hardware name: Generic DT based system
> [ 515.573777] Backtrace:
> [ 515.576272] [<80107cdc>] (dump_backtrace) from [<80107f10>]
> (show_stack+0x20/0x24)
> [ 515.583930] r7:803a5614 r6:00000009 r5:00000000 r4:9d88fe1c
> [ 515.589712] [<80107ef0>] (show_stack) from [<80690184>]
> (dump_stack+0x20/0x28)
> [ 515.597053] [<80690164>] (dump_stack) from [<80116044>]
> (__warn.part.3+0xb4/0xdc)
> [ 515.604557] [<80115f90>] (__warn.part.3) from [<801160d8>]
> (warn_slowpath_fmt+0x6c/0x90)
> [ 515.612734] r6:000002ac r5:8080befc r4:80a07008
> [ 515.617463] [<80116070>] (warn_slowpath_fmt) from [<803a5614>]
> (clk_core_unprepare+0x13c/0x170)
> [ 515.626167] r3:8080cdf4 r2:8080bfc0
> [ 515.629834] r7:98d682a8 r6:9d8a9200 r5:9e5151a0 r4:97abd620
> [ 515.635530] [<803a54d8>] (clk_core_unprepare) from [<803a76a4>]
> (clk_unprepare+0x34/0x3c)
> [ 515.643812] r5:9e5151a0 r4:97abd620
> [ 515.647529] [<803a7670>] (clk_unprepare) from [<804f36ec>]
> (aspeed_video_off+0x38/0x50)
> [ 515.655539] r5:9e5151a0 r4:9e504000
> [ 515.659242] [<804f36b4>] (aspeed_video_off) from [<804f4358>]
> (aspeed_video_release+0x90/0x114)
> [ 515.668036] r5:9e5044b0 r4:9e504000
> [ 515.671643] [<804f42c8>] (aspeed_video_release) from [<804d302c>]
> (v4l2_release+0xd4/0xe8)
> [ 515.679999] r7:98d682a8 r6:9d087810 r5:9d8a9200 r4:9e504318
> [ 515.685695] [<804d2f58>] (v4l2_release) from [<80236454>]
> (__fput+0x98/0x1c4)
> [ 515.692914] r5:9e51b608 r4:9d8a9200
> [ 515.696597] [<802363bc>] (__fput) from [<802365e8>]
> (____fput+0x18/0x1c)
> [ 515.703315] r9:80a0700c r8:801011e4 r7:00000000 r6:80a64b9c
> r5:9d8e35a0 r4:9d8e38dc
> [ 515.711167] [<802365d0>] (____fput) from [<80131ca4>]
> (task_work_run+0x7c/0xa0)
> [ 515.718596] [<80131c28>] (task_work_run) from [<80106884>]
> (do_work_pending+0x4a8/0x578)
> [ 515.726777] r7:801011e4 r6:80a07008 r5:9d88ffb0 r4:ffffe000
> [ 515.732466] [<801063dc>] (do_work_pending) from [<8010106c>]
> (slow_work_pending+0xc/0x20)
> [ 515.740727] Exception stack(0x9d88ffb0 to 0x9d88fff8)
> [ 515.745840] ffa0: 00000000
> 76f18094 00000000 00000000
> [ 515.754122] ffc0: 00000007 00176778 7eda4c20 00000006 00000000
> 00000000 48e20fa4 00000000
> [ 515.762386] ffe0: 00000002 7eda4b08 00000000 48f91efc 80000010
> 00000007
> [ 515.769097] r10:00000000 r9:9d88e000 r8:801011e4 r7:00000006
> r6:7eda4c20 r5:00176778
> [ 515.777006] r4:00000007
> [ 515.779558] ---[ end trace 12c04aadef8afbbb ]---
> [ 515.784176] ------------[ cut here ]------------
> [ 515.788817] WARNING: CPU: 0 PID: 1310 at drivers/clk/clk.c:825
> clk_core_disable+0x18c/0x204
> [ 515.797161] eclk-gate already disabled
> [ 515.800916] CPU: 0 PID: 1310 Comm: obmc-ikvm Tainted:
> G W 5.0.6-df66fbc97853fbba90a0bfa44de32f3d5f7602b4 #1
> [ 515.811945] Hardware name: Generic DT based system
> [ 515.816730] Backtrace:
> [ 515.819210] [<80107cdc>] (dump_backtrace) from [<80107f10>]
> (show_stack+0x20/0x24)
> [ 515.826782] r7:803a5900 r6:00000009 r5:00000000 r4:9d88fe04
> [ 515.832454] [<80107ef0>] (show_stack) from [<80690184>]
> (dump_stack+0x20/0x28)
> [ 515.839687] [<80690164>] (dump_stack) from [<80116044>]
> (__warn.part.3+0xb4/0xdc)
> [ 515.847170] [<80115f90>] (__warn.part.3) from [<801160d8>]
> (warn_slowpath_fmt+0x6c/0x90)
> [ 515.855247] r6:00000339 r5:8080befc r4:80a07008
> [ 515.859868] [<80116070>] (warn_slowpath_fmt) from [<803a5900>]
> (clk_core_disable+0x18c/0x204)
> [ 515.868385] r3:8080cdd0 r2:8080c00c
> [ 515.871957] r7:98d682a8 r6:9d8a9200 r5:97abd560 r4:97abd560
> [ 515.877615] [<803a5774>] (clk_core_disable) from [<803a59a0>]
> (clk_core_disable_lock+0x28/0x34)
> [ 515.886301] r7:98d682a8 r6:9d8a9200 r5:97abd560 r4:a0000013
> [ 515.891960] [<803a5978>] (clk_core_disable_lock) from [<803a7714>]
> (clk_disable+0x2c/0x30)
> [ 515.900216] r5:9e5151a0 r4:9e515f60
> [ 515.903816] [<803a76e8>] (clk_disable) from [<804f36f8>]
> (aspeed_video_off+0x44/0x50)
> [ 515.911656] [<804f36b4>] (aspeed_video_off) from [<804f4358>]
> (aspeed_video_release+0x90/0x114)
> [ 515.920341] r5:9e5044b0 r4:9e504000
> [ 515.923921] [<804f42c8>] (aspeed_video_release) from [<804d302c>]
> (v4l2_release+0xd4/0xe8)
> [ 515.932184] r7:98d682a8 r6:9d087810 r5:9d8a9200 r4:9e504318
> [ 515.937851] [<804d2f58>] (v4l2_release) from [<80236454>]
> (__fput+0x98/0x1c4)
> [ 515.944980] r5:9e51b608 r4:9d8a9200
> [ 515.948559] [<802363bc>] (__fput) from [<802365e8>]
> (____fput+0x18/0x1c)
> [ 515.955257] r9:80a0700c r8:801011e4 r7:00000000 r6:80a64b9c
> r5:9d8e35a0 r4:9d8e38dc
> [ 515.963008] [<802365d0>] (____fput) from [<80131ca4>]
> (task_work_run+0x7c/0xa0)
> [ 515.970333] [<80131c28>] (task_work_run) from [<80106884>]
> (do_work_pending+0x4a8/0x578)
> [ 515.978421] r7:801011e4 r6:80a07008 r5:9d88ffb0 r4:ffffe000
> [ 515.984086] [<801063dc>] (do_work_pending) from [<8010106c>]
> (slow_work_pending+0xc/0x20)
> [ 515.992247] Exception stack(0x9d88ffb0 to 0x9d88fff8)
> [ 515.997296] ffa0: 00000000
> 76f18094 00000000 00000000
> [ 516.005473] ffc0: 00000007 00176778 7eda4c20 00000006 00000000
> 00000000 48e20fa4 00000000
> [ 516.013642] ffe0: 00000002 7eda4b08 00000000 48f91efc 80000010
> 00000007
> [ 516.020257] r10:00000000 r9:9d88e000 r8:801011e4 r7:00000006
> r6:7eda4c20 r5:00176778
> [ 516.028072] r4:00000007
> [ 516.030606] ---[ end trace 12c04aadef8afbbc ]---
>
> To prevent this issue, this commit adds spinlock protection and
> clock status checking logic into the Aspeed video engine driver.
>
> Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@xxxxxxxxxxxxxxx>
> Reviewed-by: Eddie James <eajames@xxxxxxxxxxxxx>
> ---
> 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 55c55a68b016..2dac6d20b180 100644
> --- a/drivers/media/platform/aspeed-video.c
> +++ b/drivers/media/platform/aspeed-video.c
> @@ -187,6 +187,7 @@ enum {
> VIDEO_STREAMING,
> VIDEO_FRAME_INPRG,
> VIDEO_STOPPED,
> + VIDEO_CLOCKS_ON,
> };
>
> struct aspeed_video_addr {
> @@ -483,19 +484,29 @@ static void
> aspeed_video_enable_mode_detect(struct aspeed_video *video)
>
> static void aspeed_video_off(struct aspeed_video *video)
> {
> + if (!test_bit(VIDEO_CLOCKS_ON, &video->flags))
> + return;
> +
> /* Disable interrupts */
> aspeed_video_write(video, VE_INTERRUPT_CTRL, 0);
>
> /* 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);
> +
> + set_bit(VIDEO_CLOCKS_ON, &video->flags);
> }
>
> static void aspeed_video_bufs_done(struct aspeed_video *video,
> @@ -513,12 +524,14 @@ 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);
> @@ -938,9 +951,13 @@ 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);
> @@ -956,6 +973,9 @@ 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);
>
> @@ -969,6 +989,7 @@ 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,
> @@ -1306,16 +1327,21 @@ 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 ||
