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	<1449058982-18595-3-git-send-email-Liviu.Dudau@arm.com>
Date: Wed, 2 Dec 2015 17:21:44 +0000
Message-ID: <CAPj87rNFFGeL8z9GBXxyVri1RyhVpMGS0yz7opgCYamHYV1Yow@mail.gmail.com>
Subject: Re: [PATCH v3 2/4] drm: Add support for ARM's HDLCD controller.
From: Daniel Stone <daniel@fooishbar.org>
To: Liviu Dudau <Liviu.Dudau@arm.com>
Cc: David Airlie <airlied@linux.ie>, Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>, Rob Herring <robh+dt@kernel.org>,
        Sudeep Holla <sudeep.holla@arm.com>, Jon Medhurst <tixy@linaro.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Ian Campbell <ijc+devicetree@hellion.org.uk>,
        Kumar Gala <galak@codeaurora.org>, Rob Herring <robh@kernel.org>,
        Russell King <rmk+kernel@arm.linux.org.uk>,
        devicetree <devicetree@vger.kernel.org>,
        Pawel Moll <pawel.moll@arm.com>, Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Punit Agrawal <punit.agrawal@arm.com>,
        LKML <linux-kernel@vger.kernel.org>,
        DRI devel <dri-devel@lists.freedesktop.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Robin Murphy <robin.murphy@arm.com>,
        LAKML <linux-arm-kernel@lists.infradead.org>
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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
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