linux-kernel - Re: [PATCH 13/23] drm: omapdrm: crtc: update plane fifos on lcd config change

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Message-ID: <3716864.g0dovaDAJW@avalon>
Date:	Sat, 26 Mar 2016 19:00:53 +0200
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Sebastian Reichel <sre@...nel.org>
Cc:	Tony Lindgren <tony@...mide.com>,
	Aaro Koskinen <aaro.koskinen@....fi>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	David Airlie <airlied@...ux.ie>, linux-omap@...r.kernel.org,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 13/23] drm: omapdrm: crtc: update plane fifos on lcd config change

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@...nel.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