From nobody Wed Apr 8 10:33:07 2026 Received: from mail-pl1-f179.google.com (mail-pl1-f179.google.com [209.85.214.179]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A017A3A2576 for ; Thu, 19 Mar 2026 08:32:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.179 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773909145; cv=none; b=XEmgwd9iaGFFbgRAbxaZLDBMfTPUmnRqJISJ8es/EysXfYPZcbPJUJdMU81nxJ/VqhIMXEddXuPv06FGnN+rR9C9AfsU9nRhOrIXavxgMtnLG8u1bEWeL5TMBRcihKpy4AnPD2VNOhCBy1Ti1p1fr2OtGkmaavHJaxhiohaKTm0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773909145; c=relaxed/simple; bh=SC29zW4VcpmHk7y/5BpagzpL5n5QvsDOhzfIPZ3UGHs=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=sgRO8PAfv3OIPKUFU14AHNe7vAVDvnKBUHblJvKwvrcj9lfDPOqlJAhFq1ISK2BpJVfwUn99YiIxMwKj+Y+mHY+nyBmr93Q+TF6HUzaBKm4z/KrqirAbACH71F0pwVkURRxnmaZ4qQoq/BIYrEEUeZELePkgcEo25cuhsBxk8L8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=SIWLP6Qc; arc=none smtp.client-ip=209.85.214.179 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="SIWLP6Qc" Received: by mail-pl1-f179.google.com with SMTP id d9443c01a7336-2ad21f437eeso5754215ad.0 for ; Thu, 19 Mar 2026 01:32:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1773909144; x=1774513944; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=VqOOQO8G00f+NnUwp116p4eShMIJWuolK06DttQTATw=; b=SIWLP6Qc8cqRmSVKnQTObKCJLsrPFrOEN0Qv8L0Gya6B8W1VAJC2jKtyTfeBwQJCvO RnDCMLrFWulv6vTxu7sE/x22vKMEx9MY5vAJlXSm/Zdx0ksfSOjZOHhMdrsdHZ0r2foz tBq1FjcGdAdm5y5ciqLExIomDezUH9QR/9WylKaSkQ/6+xfHIXu7Smrrl0WzRtnXEIGt EUIKCo7GZGzxhC9h1/Rf8tfHA8znJ692mtevFnLC3qCIkNynflLOcahfqNWDRBPQnFmC Q69F3xgUI5uWlyuw05m2txsVnED5EETKuDuuNneglmh2c0+JCyucagJlI2U9ggoxSjUt ePaA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1773909144; x=1774513944; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=VqOOQO8G00f+NnUwp116p4eShMIJWuolK06DttQTATw=; b=LhSR0/N4BQ0NVXDmYI0PUJ5GOIo3BRCJSeUjkT6puXvAzTs1p/uU/YiMy2WiqfVcs+ mMSNuyhZRhrBahycK7cVLChUs0eA5fzksxQ9IzMFPAe9JPyQVOSBxe+Buh94WLktGuV6 K0y1op+yysYPYnZ+icgZhxP7HJtRbPMQ1qCTnZwXhicZ4qocTChGtq4ZOUfZwvVaz6s6 qEe0MLVxcuPvjgyDlK9wkZN0vF2qGTC91Gd4jQic6jGS1Z9uwlTaXlGRJgWrBUOY3bRk mn0QMpYH0vOK0Y+OKsatL83NfYmFdgNA09VkJfw6zp5kFIM4Iq12vyFKp5B4fH8o09eD 5w4g== X-Forwarded-Encrypted: i=1; AJvYcCU3U3jVMMw6xpm7mDZzzQyoKfJSeDKMvaD8gnIW1UTlOR4Fw2dhA0GsSayxghXnX+Rb8a/FfPW2T7nA5RY=@vger.kernel.org X-Gm-Message-State: AOJu0Ywe+SonI5Puz3VK6/x1dr95zkqzPwMcop0Ip4oQdbpxZ8wMX/KJ HcsTj8JzCjRRfcWLaa8KYy+yYw3jUvWV+NNxyMlU4J/Fw9e4VIvzWrLXbif/pw== X-Gm-Gg: ATEYQzwi2ieHLnTDteS8GRN1G66xqK5JkytQrpEBWm6M+OExWr2B/HVI2zOdwjYEmjD ihY4XE6TCzDLhVUy00DhZOLwXRiNK9bNjz+yk98sV0NBVIjCdSPi74wFZ0WRfjHvjBYQJOrBwkD QnBXqoK45tFawzm+Q3DQKcpS0HcHJsnHAjrBn3fBl2BkeaQ0bwqi8BtPN5g307pYhdFdDt15zB3 HttTUgzvRXBM2MQyAUvU8ElmocIDKMlQmRVlgZLkr3gY25MMsT1fhCbjIl8No+tUf+alJZD9/Ir xm8/ubaOhXmVk7xtTRidIc7S/9kV4rbeCwFo4NQ7w2qIlfEwWIcp9WXvCHUilxh8oHpHfbgABbY SERKdwDCx1v2McgyShgjPT376A7FvpsM4pyZnv3YEO3gmw18Be+p3LSVOylrTEK7vQ/0SxNE7uW VvRNs6866cDy8lKTQQH+RPliw/dMiBaTP3cU9bCEGvmn8bdl3Ngl4eeyrmQA== X-Received: by 2002:a17:903:38c5:b0:2b0:6ba2:3d32 with SMTP id d9443c01a7336-2b07716eb19mr29493095ad.2.1773909143843; Thu, 19 Mar 2026 01:32:23 -0700 (PDT) Received: from phuc-desktop.. ([183.91.15.56]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b06e603b2asm53581615ad.55.2026.03.19.01.32.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Mar 2026 01:32:23 -0700 (PDT) From: phucduc.bui@gmail.com To: Cc: phucduc.bui@gmail.com, airlied@gmail.com, dri-devel@lists.freedesktop.org, geert@linux-m68k.org, laurent.pinchart@ideasonboard.com, linux-kernel@vger.kernel.org, linux-renesas-soc@vger.kernel.org, maarten.lankhorst@linux.intel.com, mripard@kernel.org, simona@ffwll.ch, tzimmermann@suse.de, wsa+renesas@sang-engineering.com, Geert Uytterhoeven Subject: [PATCH v3] drm: shmobile: Fix white screen after resume when LCDC is stopped Date: Thu, 19 Mar 2026 15:31:49 +0700 Message-ID: <20260319083207.17195-1-phucduc.bui@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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=3D0), 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 --- Changes: - v3=20 Update commit message, add Tested-by and Reviewed-by tags=20 - v2=20 Fix incorrect use of lcdc_write_mirror() for LDSA2R in the DO=3D0 path; use lcdc_write() to update both register sets as intended. .../gpu/drm/renesas/shmobile/shmob_drm_plane.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/renesas/shmobile/shmob_drm_plane.c b/drivers/g= pu/drm/renesas/shmobile/shmob_drm_plane.c index b61fda52d17a..23c8489dba71 100644 --- a/drivers/gpu/drm/renesas/shmobile/shmob_drm_plane.c +++ b/drivers/gpu/drm/renesas/shmobile/shmob_drm_plane.c @@ -70,6 +70,7 @@ static void shmob_drm_primary_plane_setup(struct shmob_dr= m_plane *splane, struct shmob_drm_plane_state *sstate =3D to_shmob_plane_state(state); struct shmob_drm_device *sdev =3D to_shmob_device(splane->base.dev); struct drm_framebuffer *fb =3D state->fb; + u32 ldcnt2r; =20 /* TODO: Handle YUV colorspaces. Hardcode REC709 for now. */ lcdc_write(sdev, LDDFR, sstate->format->lddfr | LDDFR_CF1); @@ -78,11 +79,19 @@ static void shmob_drm_primary_plane_setup(struct shmob_= drm_plane *splane, /* Word and long word swap. */ lcdc_write(sdev, LDDDSR, sstate->format->ldddsr); =20 - lcdc_write_mirror(sdev, LDSA1R, sstate->dma[0]); - if (shmob_drm_format_is_yuv(sstate->format)) - lcdc_write_mirror(sdev, LDSA2R, sstate->dma[1]); + ldcnt2r =3D lcdc_read(sdev, LDCNT2R); + + if (ldcnt2r & LDCNT2R_DO) { + lcdc_write_mirror(sdev, LDSA1R, sstate->dma[0]); + if (shmob_drm_format_is_yuv(sstate->format)) + lcdc_write_mirror(sdev, LDSA2R, sstate->dma[1]); =20 - lcdc_write(sdev, LDRCNTR, lcdc_read(sdev, LDRCNTR) ^ LDRCNTR_MRS); + lcdc_write(sdev, LDRCNTR, lcdc_read(sdev, LDRCNTR) ^ LDRCNTR_MRS); + } else { + lcdc_write(sdev, LDSA1R, sstate->dma[0]); + if (shmob_drm_format_is_yuv(sstate->format)) + lcdc_write(sdev, LDSA2R, sstate->dma[1]); + } } =20 static void shmob_drm_overlay_plane_setup(struct shmob_drm_plane *splane, --=20 2.43.0