linux-kernel - Re: [PATCH v9 2/5] drm/sun4i: sun6i_mipi

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Message-ID: <20190304154320.uledvwz5jhzt22o3@flea>
Date:   Mon, 4 Mar 2019 16:43:20 +0100
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Jagan Teki <jagan@...rulasolutions.com>
Cc:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Chen-Yu Tsai <wens@...e.org>, dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-amarula@...rulasolutions.com,
        Michael Trimarchi <michael@...rulasolutions.com>,
        linux-sunxi@...glegroups.com
Subject: Re: [PATCH v9 2/5] drm/sun4i: sun6i_mipi_dsi: Fix TCON DRQ set bits

On Sun, Mar 03, 2019 at 11:05:24PM +0530, Jagan Teki wrote:
> TCON DRQ for non-burst DSI mode can computed based on horizontal
> front porch value, but the current driver trying to include sync
> timings along with front porch resulting wrong drq.
> 
> This patch is trying to update the drq by subtracting hsync_start
> with hdisplay, which is horizontal front porch.
> 
> Current code:
> ------------
> mode->hsync_end - mode->hdisplay => horizontal front porch + sync
> 
> With this patch:
> ----------------
> mode->hsync_start - mode->hdisplay => horizontal front porch
> 
> BSP code form BPI-M64-bsp is computing TCON DRQ set bits
> for non-burts as (from linux-sunxi/
> drivers/video/sunxi/disp2/disp/de/lowlevel_sun50iw1/de_dsi.c)
> 
> => panel->lcd_ht -    panel->lcd_x - panel->lcd_hbp
> => (timmings->hor_front_porch + panel->lcd_hbp + panel->lcd_x)
                                  ^ + sync length +          
>    - panel->lcd_x - panel->hbp
> => timmings->hor_front_porch
                               ^ + sync
> => mode->hsync_start - mode->hdisplay

s/hsync_start/hsync_end/

Did you encounter any panel where this was fixing something? If so,
which one, and what is the matching timings and / or datasheet?

Maxime

-- 
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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