[PATCH 19/38] drm/hisilicon: Implement some semblance of vblank event handling

[Xinliang Liu]

Hi Daniel,

I have tested your David's drm-next branch[1] which including this patch.
In most time it is ok. But when switching modes or disable/re-enable
mode, it will encounter bellow error msg:
--
[  357.940728] [drm:drm_atomic_helper_commit_cleanup_done] *ERROR*
[CRTC:24:crtc-0] flip_done timed out
[  368.004962] [drm:drm_atomic_helper_commit_cleanup_done] *ERROR*
[CRTC:24:crtc-0] flip_done timed out
[  396.064871] INFO: rcu_preempt detected stalls on CPUs/tasks:
[  396.070548]  0-...: (3 GPs behind) idle=f4f/1/0 softirq=4253/4253 fqs=19
[  396.077335]  7-...: (1 GPs behind) idle=71f/140000000000000/0
softirq=2444/2451 fqs=19
[  396.085332]  (detected by 1, t=6028 jiffies, g=3924, c=3923, q=246)
[  396.091600] Task dump for CPU 0:
[  396.094821] swapper/0       R  running task        0     0      0 0x00000002
[  396.101872] Call trace:
[  396.104323] [<ffff000008085bec>] __switch_to+0xa4/0xd4
[  396.109460] [<ffff000008c85000>] __boot_cpu_mode+0x0/0x80
[  396.114852] Task dump for CPU 7:
[  396.118072] Xorg            R  running task        0  1658   1646 0x00000002
[  396.125121] Call trace:
[  396.127562] [<ffff000008085c10>] __switch_to+0xc8/0xd4
[  396.132695] [<ffff800035567110>] 0xffff800035567110
[  396.137569] rcu_preempt kthread starved for 1000 jiffies! g3924
c3923 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x1
[  396.147130] rcu_preempt     S ffff000008085c10     0     7      2 0x00000000
[  396.154180] Call trace:
[  396.156620] [<ffff000008085c10>] __switch_to+0xc8/0xd4
[  396.161758] [<ffff000008810490>] __schedule+0x188/0x590
[  396.166978] [<ffff0000088108d4>] schedule+0x3c/0xa0
[  396.171851] [<ffff00000881368c>] schedule_timeout+0x104/0x1a4
[  396.177595] [<ffff00000810549c>] rcu_gp_kthread+0x54c/0x814
[  396.183164] [<ffff0000080d3e5c>] kthread+0xd4/0xe8
[  396.187951] [<ffff000008084e10>] ret_from_fork+0x10/0x40
--

Then the console stuck. Any tips for addressing this issue?
I am running a debian system.

[1] git://people.freedesktop.org/~airlied/linux drm-next

Thanks,
-xinliang

On 2 June 2016 at 06:06, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
> atomic_flush seems to be the right place, but I'm not entirely sure
> whether this will catch them all. It could be that when disabling the
> crtc we'll miss the vblank.
>
> While at it nuke the dummy functions.
>
> v2: Be more robust and either arm, when the CRTC is on, or just send
> the event out right away.
>
> Cc: Xinliang Liu <xinliang.liu at linaro.org>
> Cc: Xinwei Kong <kong.kongxinwei at hisilicon.com>
> Cc: Archit Taneja <architt at codeaurora.org>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>

Acked-by: Xinliang Liu <xinliang.liu at linaro.org>

> ---
>  drivers/gpu/drm/hisilicon/kirin/kirin_drm_ade.c | 20 ++++++++++++--------
>  1 file changed, 12 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/hisilicon/kirin/kirin_drm_ade.c b/drivers/gpu/drm/hisilicon/kirin/kirin_drm_ade.c
> index fba6372d060e..ed76baad525f 100644
> --- a/drivers/gpu/drm/hisilicon/kirin/kirin_drm_ade.c
> +++ b/drivers/gpu/drm/hisilicon/kirin/kirin_drm_ade.c
> @@ -502,13 +502,6 @@ static void ade_crtc_disable(struct drm_crtc *crtc)
>         acrtc->enable = false;
>  }
>
> -static int ade_crtc_atomic_check(struct drm_crtc *crtc,
> -                                struct drm_crtc_state *state)
> -{
> -       /* do nothing */
> -       return 0;
> -}
> -
>  static void ade_crtc_mode_set_nofb(struct drm_crtc *crtc)
>  {
>         struct ade_crtc *acrtc = to_ade_crtc(crtc);
> @@ -537,6 +530,7 @@ static void ade_crtc_atomic_flush(struct drm_crtc *crtc,
>  {
>         struct ade_crtc *acrtc = to_ade_crtc(crtc);
>         struct ade_hw_ctx *ctx = acrtc->ctx;
> +       struct drm_pending_vblank_event *event = crtc->state->event;
>         void __iomem *base = ctx->base;
>
>         /* only crtc is enabled regs take effect */
> @@ -545,12 +539,22 @@ static void ade_crtc_atomic_flush(struct drm_crtc *crtc,
>                 /* flush ade registers */
>                 writel(ADE_ENABLE, base + ADE_EN);
>         }
> +
> +       if (event) {
> +               crtc->state->event = NULL;
> +
> +               spin_lock_irq(&crtc->dev->event_lock);
> +               if (drm_crtc_vblank_get(crtc) == 0)
> +                       drm_crtc_arm_vblank_event(crtc, event);
> +               else
> +                       drm_crtc_send_vblank_event(crtc, event);
> +               spin_unlock_irq(&crtc->dev->event_lock);
> +       }
>  }
>
>  static const struct drm_crtc_helper_funcs ade_crtc_helper_funcs = {
>         .enable         = ade_crtc_enable,
>         .disable        = ade_crtc_disable,
> -       .atomic_check   = ade_crtc_atomic_check,
>         .mode_set_nofb  = ade_crtc_mode_set_nofb,
>         .atomic_begin   = ade_crtc_atomic_begin,
>         .atomic_flush   = ade_crtc_atomic_flush,
> --
> 2.8.1
>