Re: [PATCH v3 2/4] drm: Add support for ARM's HDLCD controller.

[Daniel Stone]

Hi Liviu,

On 2 December 2015 at 12:23, Liviu Dudau <Liviu.Dudau@xxxxxxx> wrote:
> +       if (irq_status & HDLCD_INTERRUPT_VSYNC) {
> +               unsigned long flags;
> +
> +               drm_handle_vblank(drm, 0);
> +
> +               spin_lock_irqsave(&drm->event_lock, flags);
> +               if (hdlcd->event) {
> +                       drm_send_vblank_event(drm, hdlcd->event->pipe, hdlcd->event);
> +                       drm_crtc_vblank_put(&hdlcd->crtc);
> +                       hdlcd->event = NULL;
> +               }
> +               spin_unlock_irqrestore(&drm->event_lock, flags);
> +       }

As with VC4 and Rockchip, you're missing a ->preclose handler in your
drm_drv, to make sure that you don't try to send events to a dead
client (which causes an OOPS):
https://git.collabora.com/cgit/user/daniels/linux.git/commit/?h=wip/4.4.x/rockchip-drm-fixes&id=d14f21bcd7
(and its parent)

Also, is there anything preventing clients from submitting multiple
pageflips before the event is sent? I couldn't see anything from a
quick look, so you could have the situation of:
  - client submits pageflip, event 1 stored to hdlcd->event
  - client submits pageflip, event 2 stored to hdlcd->event
  - vblank arrives, event 2 is sent
  - event 1 has disappeared and been leaked

Cheers,
Daniel
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