From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxime Ripard Subject: Re: [PATCH v8 01/15] drm/sun4i: dsi: Fix video start delay computation Date: Mon, 11 Mar 2019 16:37:34 +0100 Message-ID: <20190311153734.izg44ijwqqh2vpxc@flea> References: <20190311133637.18334-1-jagan@amarulasolutions.com> <20190311133637.18334-2-jagan@amarulasolutions.com> Reply-To: maxime.ripard-LDxbnhwyfcJBDgjK7y7TUQ@public.gmane.org Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="gkffxe7wlup45xq3" Return-path: Sender: linux-sunxi-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org Content-Disposition: inline In-Reply-To: <20190311133637.18334-2-jagan-dyjBcgdgk7Pe9wHmmfpqLFaTQe2KTcn/@public.gmane.org> List-Post: , List-Help: , List-Archive: , List-Unsubscribe: , To: Jagan Teki Cc: David Airlie , Daniel Vetter , Chen-Yu Tsai , Michael Turquette , Rob Herring , Mark Rutland , linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-clk-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Michael Trimarchi , linux-amarula-dyjBcgdgk7Pe9wHmmfpqLFaTQe2KTcn/@public.gmane.org, linux-sunxi-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org List-Id: dri-devel@lists.freedesktop.org --gkffxe7wlup45xq3 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline On Mon, Mar 11, 2019 at 07:06:23PM +0530, Jagan Teki wrote: > Vertical video start delay is computed by excluding vertical front > porch value from total vertical timings. > > This clearly confirmed from BSP code and here how it computed, > > (drivers/video/sunxi/disp2/disp/de/lowlevel_sun50iw1/de_dsi.c) > u32 vfp = panel->lcd_vt - panel->lcd_y - panel->lcd_vbp; > => (panel->lcd_vt) - panel->lcd_y - (panel->lcd_vbp) > => (timmings->ver_front_porch + panel->lcd_vbp + panel->lcd_y) > - panel->lcd_y - (panel->lcd_vbp) > => timmings->ver_front_porch + panel->lcd_vbp + panel->lcd_y > - panel->lcd_y - panel->lcd_vbp > => timmings->ver_front_porch > > But the current driver is assuming it can exclude vertical front > porch along with vertical sync values from total vertical timings, > which resulting wrong start delay indeed wrong picture rendering > in the panel. Same story here: which panel, which datasheet, which "wrong picture rendering"? > Example: timings, where it produces the issue. > { > .vdisplay = 600, > .vsync_start = 600 + 12, > .vsync_end = 600 + 12 + 2, > .vtotal = 600 + 12 + 2 + 21, > } Can you 100% trust those timings? > It produces the desired start delay value as 19 but the correct working > value should be 513. > > So, Fix it by computing proper video start delay. > > Fixes: 69006ef0ecb1 ("drm/sun4i: dsi: Change the start delay calculation") > Signed-off-by: Jagan Teki > --- > drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c > index 62a508420227..8d6292c0158b 100644 > --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c > +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c > @@ -364,8 +364,14 @@ static void sun6i_dsi_inst_init(struct sun6i_dsi *dsi, > static u16 sun6i_dsi_get_video_start_delay(struct sun6i_dsi *dsi, > struct drm_display_mode *mode) > { > - u16 start = clamp(mode->vtotal - mode->vdisplay - 10, 8, 100); > - u16 delay = mode->vtotal - (mode->vsync_end - mode->vdisplay) + start; > + u16 delay = mode->vtotal - (mode->vsync_start - mode->vdisplay); > + > + /** > + * BSP comment: > + * put start_delay to tcon. set ready sync early to dramfreq, > + * so set start_delay 1 > + */ That doesn't make any sense to me... What does it mean? Maxime -- Maxime Ripard, Bootlin Embedded Linux and Kernel engineering https://bootlin.com --gkffxe7wlup45xq3--