From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Sebastian Reichel <sre@kernel.org>
Cc: Tony Lindgren <tony@atomide.com>, Aaro Koskinen <aaro.koskinen@iki.fi>,
        Tomi Valkeinen <tomi.valkeinen@ti.com>,
        David Airlie <airlied@linux.ie>, linux-omap@vger.kernel.org,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 13/23] drm: omapdrm: crtc: update plane fifos on lcd config change
Date: Sat, 26 Mar 2016 19:00:53 +0200
Message-ID: <3716864.g0dovaDAJW@avalon>
User-Agent: KMail/4.14.10 (Linux/4.1.15-gentoo-r1; KDE/4.14.16; x86_64; ; )
In-Reply-To: <1457455195-1938-14-git-send-email-sre@kernel.org>
References: <1457455195-1938-1-git-send-email-sre@kernel.org> <1457455195-1938-14-git-send-email-sre@kernel.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 7Bit
Content-Type: text/plain; charset="us-ascii"
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1301
Lines: 44

Hi Sebastian,

Thank you for the patch.

On Tuesday 08 Mar 2016 17:39:45 Sebastian Reichel wrote:
> Due to a hardware bug, FIFOs thresholds must be
> configured very carefully for manually updated
> displays.

Could you please provide more information about the bug and how the code 
handles it ?

> Signed-off-by: Sebastian Reichel <sre@kernel.org>
> ---
>  drivers/gpu/drm/omapdrm/omap_crtc.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/gpu/drm/omapdrm/omap_crtc.c
> b/drivers/gpu/drm/omapdrm/omap_crtc.c index 8967013c1fb5..094e89a2fa94
> 100644
> --- a/drivers/gpu/drm/omapdrm/omap_crtc.c
> +++ b/drivers/gpu/drm/omapdrm/omap_crtc.c
> @@ -253,6 +253,10 @@ static void omap_crtc_dss_set_lcd_config(struct
> omap_overlay_manager *mgr, omap_crtc->manually_updated =
> dss_lcd_mgr_config_get_stallmode(config);
> 
>  	dispc_mgr_set_lcd_config(omap_crtc->channel, config);
> +
> +	drm_for_each_plane(plane, dev) {
> +		omap_plane_update_fifo(plane);
> +	}

This seems fishy :-/ To start with you shouldn't touch planes that don't 
belong to this CRTC. Then, updating the FIFO thresholds here in addition to 
omap_plane_atomic_update() makes me wonder if both are needed, and if so, why.

>  }
> 
>  static int omap_crtc_dss_register_framedone(

-- 
Regards,

Laurent Pinchart