linux-kernel - Re: [PATCH 5.2 048/215] drm/omap: dont check dispc timings for DSI

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Message-ID: <20190730113751.GB21815@amd>
Date:   Tue, 30 Jul 2019 13:37:51 +0200
From:   Pavel Machek <pavel@...x.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Tony Lindgren <tony@...mide.com>,
        Sebastian Reichel <sebastian.reichel@...labora.com>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 5.2 048/215] drm/omap: dont check dispc timings for DSI

On Mon 2019-07-29 21:20:44, Greg Kroah-Hartman wrote:
> [ Upstream commit ad9df7d91b4a6e8f4b20c2bf539ac09b3b2ad6eb ]
> 
> While most display types only forward their VM to the DISPC, this
> is not true for DSI. DSI calculates the VM for DISPC based on its
> own, but it's not identical. Actually the DSI VM is not even a valid
> DISPC VM making this check fail. Let's restore the old behaviour
> and avoid checking the DISPC VM for DSI here.
> 
> Fixes: 7c27fa57ef31 ("drm/omap: Call dispc timings check operation directly")
> Acked-by: Pavel Machek <pavel@....cz>
> Tested-by: Tony Lindgren <tony@...mide.com>
> Tested-by: Pavel Machek <pavel@....cz>
> Signed-off-by: Sebastian Reichel <sebastian.reichel@...labora.com>
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...com>
> Signed-off-by: Sasha Levin <sashal@...nel.org>

Not sure if this is good idea for stable. IIRC there's series of
patches to enable display on droid4 (etc), which is useful, but this
patch is not going to do any good on its own.

								Pavel

>  drivers/gpu/drm/omapdrm/omap_crtc.c | 18 ++++++++++++++----
>  1 file changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/omapdrm/omap_crtc.c b/drivers/gpu/drm/omapdrm/omap_crtc.c
> index 8712af79a49c..4c43dd282acc 100644
> --- a/drivers/gpu/drm/omapdrm/omap_crtc.c
> +++ b/drivers/gpu/drm/omapdrm/omap_crtc.c
> @@ -384,10 +384,20 @@ static enum drm_mode_status omap_crtc_mode_valid(struct drm_crtc *crtc,
>  	int r;
>  
>  	drm_display_mode_to_videomode(mode, &vm);
> -	r = priv->dispc_ops->mgr_check_timings(priv->dispc, omap_crtc->channel,
> -					       &vm);
> -	if (r)
> -		return r;
> +
> +	/*
> +	 * DSI might not call this, since the supplied mode is not a
> +	 * valid DISPC mode. DSI will calculate and configure the
> +	 * proper DISPC mode later.
> +	 */
> +	if (omap_crtc->pipe->output->next == NULL ||
> +	    omap_crtc->pipe->output->next->type != OMAP_DISPLAY_TYPE_DSI) {
> +		r = priv->dispc_ops->mgr_check_timings(priv->dispc,
> +						       omap_crtc->channel,
> +						       &vm);
> +		if (r)
> +			return r;
> +	}
>  
>  	/* Check for bandwidth limit */
>  	if (priv->max_bandwidth) {

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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