From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_NEOMUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2115AC4360F for ; Tue, 19 Mar 2019 10:19:13 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E2B7C20857 for ; Tue, 19 Mar 2019 10:19:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="tefR54o4" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E2B7C20857 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=bootlin.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender:Content-Type:Cc: List-Subscribe:List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id: In-Reply-To:MIME-Version:References:Message-ID:Subject:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=FckucfdNusFIL5Z0ltD+VK7XUy8MW7D099rBy+WVq7w=; b=tefR54o4dUlmFqSxVgzdWTS5n Kehb6BEtE6BSiz5bj5VXdRWzTtky8LgmT2Ng6AYsieFZq6O7955Es6SPFxfC2OkapRsAD+dFITDoP QhXmn4da5NXWtEqW8kj/tNFiGIEkQx+rOfKYVzVOgKgYD5jXsTZKWNwTod6CbkDwQITiayoR0qQVh LNiL2FCy+PPnTVAsms/zD25JbjBfXYmHSwm2996GG1P3a91NcXhlbocq/PgNsCdi+laUdZQJh3a5I L/9xk8qjP9lL8lOESe0CnzbNgkI78YAzKlup4AkzIVZ3Btf4l1te7zddCCIGYAMcdV7IstMbiG88K Nd1TmEIRQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1h6Bpr-0002vi-73; Tue, 19 Mar 2019 10:19:07 +0000 Received: from relay1-d.mail.gandi.net ([217.70.183.193]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1h6Bpm-0002vB-LI for linux-arm-kernel@lists.infradead.org; Tue, 19 Mar 2019 10:19:04 +0000 X-Originating-IP: 90.88.22.102 Received: from localhost (aaubervilliers-681-1-80-102.w90-88.abo.wanadoo.fr [90.88.22.102]) (Authenticated sender: maxime.ripard@bootlin.com) by relay1-d.mail.gandi.net (Postfix) with ESMTPSA id C53FD24000B; Tue, 19 Mar 2019 10:18:49 +0000 (UTC) Date: Tue, 19 Mar 2019 11:18:49 +0100 From: Maxime Ripard To: Jagan Teki Subject: Re: [PATCH v2 3/9] drm/sun4i: dsi: Change the start delay calculation Message-ID: <20190319101849.a5vzwfkm7sg7wh2l@flea> References: <6e5f72e68f47ca0223877464bf12f0c3f3978de8.1549619502.git-series.maxime.ripard@bootlin.com> <20190311141211.uhxtrrdkp3q3dvt5@flea> MIME-Version: 1.0 In-Reply-To: User-Agent: NeoMutt/20180716 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190319_031902_996681_84AF8D48 X-CRM114-Status: GOOD ( 27.69 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: bbrezillon@kernel.org, Maarten Lankhorst , dri-devel , Paul Kocialkowski , Chen-Yu Tsai , Sean Paul , Thomas Petazzoni , Jagan Teki , linux-arm-kernel Content-Type: multipart/mixed; boundary="===============9091126294740675851==" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org --===============9091126294740675851== Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="xkiqhrup7ntr6amd" Content-Disposition: inline --xkiqhrup7ntr6amd Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Mon, Mar 11, 2019 at 08:07:29PM +0530, Jagan Teki wrote: > On Mon, Mar 11, 2019 at 7:42 PM Maxime Ripard wrote: > > > > On Thu, Mar 07, 2019 at 11:24:01PM +0530, Jagan Teki wrote: > > > Hi Maxime, > > > > > > On Fri, Feb 8, 2019 at 3:23 PM Maxime Ripard wrote: > > > > > > > > The current calculation for the video start delay in the current DSI driver > > > > is that it is the total vertical size, minus the front porch and sync length, > > > > plus 1. This equals to the active vertical size plus the back porch plus 1. > > > > > > > > That 1 is coming in the Allwinner BSP from an variable that is set to 1. > > > > However, if we look at the Allwinner BSP more closely, and especially in > > > > the "legacy" code for the display (in drivers/video/sunxi/legacy/), we can > > > > see that this variable is actually computed from the porches and the sync > > > > minus 10, clamped between 8 and 100. > > > > > > > > This fixes the start delay symptom we've seen on some panels (vblank > > > > timeouts with vertical white stripes at the bottom of the panel). > > > > > > > > Signed-off-by: Maxime Ripard > > > > --- > > > > drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 4 +++- > > > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c > > > > index 380fc527a707..9471fa695ec7 100644 > > > > --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c > > > > +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c > > > > @@ -357,7 +357,9 @@ 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) > > > > { > > > > - return mode->vtotal - (mode->vsync_end - mode->vdisplay) + 1; > > > > + u16 start = clamp(mode->vtotal - mode->vdisplay - 10, 8, 100); > > > > + > > > > + return mode->vtotal - (mode->vsync_end - mode->vdisplay) + start; > > > > } > > > > > > As you stated in commit message about result as "active vertical size > > > + Back porch" which indeed correct in reverse way of previous code. > > > but the change seems incorrect to me. > > > > > > => mode->vtotal - (mode->vsync_end - mode->vdisplay) + start > > > => mode->vtotal - (mode->vsync_end - mode->vdisplay) + (mode->vtotal - > > > mode->vdisplay) # bypass 10 for now > > > => mode->vtotal - mode->vsync_end + mode->vdisplay + mode->vtotal - > > > mode->vdisplay > > > => (mode->vtotal - mode->vsync_end) + mode->vtotal > > > => Back porch + mode->vtotal > > > > > > but not > > > => Back porch + mode->vdisplay > > > > Why do you think it should be this result? > > This is what the commit messages mentioned. which indeed true. > > "The current calculation for the video start delay in the current DSI driver > is that it is the total vertical size, minus the front porch and sync length, > plus 1. This equals to the active vertical size plus the back porch plus 1." > > But the result of the logic is > => Back porch + mode->vtotal Again, that commit was assuming that the back porch contained the sync period, which doesn't seem to be the case. So I'll ask again, what makes you say this isn't true? Maxime -- Maxime Ripard, Bootlin Embedded Linux and Kernel engineering https://bootlin.com --xkiqhrup7ntr6amd Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQRcEzekXsqa64kGDp7j7w1vZxhRxQUCXJDCCQAKCRDj7w1vZxhR xYNiAQDrmJ/NvycNpJ+wyTQDibA4L1b7QYU9OjaX8aFRzT22awD+MG1+tbeq93G5 PnpvUUfuSDI3+OZEHxeW13I1nC2Vhgs= =HnxR -----END PGP SIGNATURE----- --xkiqhrup7ntr6amd-- --===============9091126294740675851== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel --===============9091126294740675851==--