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

Daniel Stone
2015-12-02T17:21:44Z

Hi Liviu,

On 2 December 2015 at 12:23, Liviu Dudau <Liviu.Dudau@arm.com> 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