From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0DEC5606A321 for ; Wed, 11 Nov 2026 12:10:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=sang-engineering.com header.i=@sang-engineering.com header.a=rsa-sha256 header.s=k1 header.b=WkRCID3y Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 2CC7610F752; Wed, 11 Nov 2026 12:10:02 +0000 (UTC) Received: from mail.zeus03.de (zeus03.de [194.117.254.33]) by gabe.freedesktop.org (Postfix) with ESMTPS id 49F2110F752 for ; Wed, 11 Nov 2026 12:09:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= sang-engineering.com; h=date:from:to:cc:subject:message-id :references:mime-version:content-type:in-reply-to; s=k1; bh=+EtG 8CyQ59kAhcLxDyXRX3sibsUSs2m78jp4eyjdC+8=; b=WkRCID3yVbwXRqKJohqV Reen4BzE0JuLOnYgLguV7+HYnRrzpAXfIcBbRX96w++mby2m5tXCx1HDPKfe5h8S hYeryuP54O9NrT6zZuJ6doM03pKU63M6lGkx16WzhowviJL3RcZuQuBiQOgBnsC/ SRGHu1jk8X2SaH888i79a1juIRyiO7+PN/0IOB9GRp9ZJYbrU+906ocm/EwlmOY/ jgN7rvBoLKMNGifpiOSCBUe/JUyXdQT6fU14rtUCk8Z4IFT2PEToJXjIJQUEQJOc mgXe68JCGLRUNnoYHip9McVi4UmUgYXLxCErHQToQ74EMUZzUoqaENnGtaEpx3ya jg== Received: (qmail 603641 invoked from network); 11 Nov 2026 13:09:52 +0100 Received: by mail.zeus03.de with ESMTPSA (TLS_AES_256_GCM_SHA384 encrypted, authenticated); 11 Nov 2026 13:09:52 +0100 X-UD-Smtp-Session: l3s3148p1@fXCIEv9fKq0ujnun Date: Wed, 11 Nov 2026 13:09:52 +0100 From: Wolfram Sang To: phucduc.bui@gmail.com Cc: Laurent Pinchart , Geert Uytterhoeven , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Simona Vetter , dri-devel@lists.freedesktop.org, linux-renesas-soc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4] drm: shmobile: Fix white screen after resume when LCDC is stopped Message-ID: References: <20260707093004.987846-1-phucduc.bui@gmail.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260707093004.987846-1-phucduc.bui@gmail.com> X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "dri-devel" X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Tue, Jul 07, 2026 at 04:30:04PM +0700, phucduc.bui@gmail.com wrote: > From: bui duc phuc > > The LCDC on R8A7740 may show a completely white screen after resuming > from suspend (s2idle or s2ram). > > After resume, both Set A and Set B registers are reset to 0. As the > Frame End interrupt is not generated while the controller is stopped > (DO=0), the hardware register switching mechanism is not triggered. > Consequently, Set A remains at 0x00000000 even though a valid Start > Address is written to Set B, resulting in a white screen. > > This is a timing-dependent race condition. In some configurations, > debug options slow down the resume path enough for a Frame End > interrupt to occur, which can mask the issue. > > Fix this by priming both register sets with the Start Address while the > controller is stopped, ensuring a valid base address is available > immediately after resume. > > Tested-by: Geert Uytterhoeven > Reviewed-by: Geert Uytterhoeven > Signed-off-by: bui duc phuc > --- > > Note: > It was originally posted in March and has already received both > Reviewed-by and Tested-by tags. I'm resending it to bring it back > to attention in case it was overlooked. > > Changes in v4: > - No functional changes. > - Resend. Still not upstream? Who is the person to pick this up? This is a valuable fix we surely want to have.