From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxime Ripard Subject: Re: [PATCH 07/12] drm/sun4i: sun6i_mipi_dsi: Fix TCON DRQ set bits Date: Thu, 27 Sep 2018 18:58:53 +0200 Message-ID: <20180927165853.dpluekbqzat663q7@flea> References: <20180927114850.24565-1-jagan@amarulasolutions.com> <20180927114850.24565-8-jagan@amarulasolutions.com> Reply-To: maxime.ripard-LDxbnhwyfcJBDgjK7y7TUQ@public.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: Sender: linux-sunxi-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org Content-Disposition: inline In-Reply-To: <20180927114850.24565-8-jagan-dyjBcgdgk7Pe9wHmmfpqLFaTQe2KTcn/@public.gmane.org> List-Post: , List-Help: , List-Archive: , List-Unsubscribe: , To: Jagan Teki Cc: Chen-Yu Tsai , Icenowy Zheng , Jernej Skrabec , Vasily Khoruzhick , Rob Herring , Mark Rutland , Catalin Marinas , Will Deacon , David Airlie , dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org, Michael Turquette , Stephen Boyd , linux-clk-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Michael Trimarchi , linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-sunxi-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org List-Id: devicetree@vger.kernel.org On Thu, Sep 27, 2018 at 05:18:45PM +0530, Jagan Teki wrote: > TCON DRQ set bits for non-burst DSI mode can computed via > horizontal front porch instead of front porch + sync timings. > > Since there no documentation for TCON_DRQ_REG(0x7c) register > this change is taken as reference from BPI-M64-bsp. Detailing more what the issue is would be great. > Signed-off-by: Jagan Teki > --- > drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c > index 599284971ab6..9918fdb990ff 100644 > --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c > +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c > @@ -367,9 +367,9 @@ static void sun6i_dsi_setup_burst(struct sun6i_dsi *dsi, > struct mipi_dsi_device *device = dsi->device; > u32 val = 0; The computation here is in the A64 driver: if ((panel->lcd_ht - panel->lcd_x - panel->lcd_hbp) < 21) { dsi_dev[sel]->dsi_tcon_drq.bits.drq_mode = 0; } else { dsi_dev[sel]->dsi_tcon_drq.bits.drq_set = (panel->lcd_ht-panel->lcd_x-panel->lcd_hbp-20) * dsi_pixel_bits[panel->lcd_dsi_format]/(8*4); } It is testing that the sync + front porch is smaller than 21, and otherwise sets the drq. > - if ((mode->hsync_end - mode->hdisplay) > 20) { My code here is testing that the difference between hsync_end and hdisplay is superior to 20, and sets the DRQ if true. The condition is reversed, but otherwise, that difference is the front porch plus the sync length. > + if ((mode->hsync_start - mode->hdisplay) > 20) { However, you are testing for just the front porch, unlike what your commit log is saying, and unlike what allwinner's code is saying. So this deserves some explanation. Maxime -- Maxime Ripard, Bootlin Embedded Linux and Kernel engineering https://bootlin.com