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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id C623B108E1F2 for ; Thu, 19 Mar 2026 11:45:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:MIME-Version:Message-ID:Date:Subject:Cc:To:From:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References:List-Owner; bh=w3fIGi3nO3mbAcAspJa31NZf3Lp/D1S+4Ye959hPyNw=; b=wZQEEQ72w0+4k0rLYGYOm9uQA5 AZ3ItczgYnOGRHHTVecPIyvkFsBiPe5EvDJr6MH7J82WAKYEqs556qvpi0inNzRcXH3uTCfyxge6T WTAKY51pOijRzDJrG0/r0yjuKiVvq9ogZMK6hJeImX7ioTWD9Uv8qCAB8ydZ/9JtjMj2E2O9Z9RpW ZL3eVeJUNDDQ+HvCDV9vvh2Q+4Xx4fallTnJlfMJQnr7EFRu85f7LqrsEAv+Db0q0g7tCb0oVQfer Kxt9bBsiugWboBJlSLNg6vF5efI8uSG3e7qyrP/IlDqIKsJ46ukUgPxMUYyOPHpf0xKFi6sJzRPvh ViPUAMpg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1w3Bp2-0000000AZ6R-13Wi; Thu, 19 Mar 2026 11:45:52 +0000 Received: from [195.187.100.5] (helo=ni.piap.pl) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1w3Boz-0000000AZ5h-0cJy for linux-arm-kernel@lists.infradead.org; Thu, 19 Mar 2026 11:45:51 +0000 Received: from t19.piap.pl (OSB1819.piap.pl [10.0.9.19]) by ni.piap.pl (Postfix) with ESMTPS id 10210C3EEAC9; Thu, 19 Mar 2026 12:45:41 +0100 (CET) DKIM-Filter: OpenDKIM Filter v2.11.0 ni.piap.pl 10210C3EEAC9 From: =?utf-8?Q?Krzysztof_Ha=C5=82asa?= To: Marek Vasut , Stefan Agner Cc: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Frank Li , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , dri-devel@lists.freedesktop.org, imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: i.MX8MP: Fix HDMI LCDIF FIFO underruns Date: Thu, 19 Mar 2026 12:45:40 +0100 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260319_044549_364539_013C6FEB X-CRM114-Status: UNSURE ( 5.47 ) X-CRM114-Notice: Please train this message. X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Running (and terminating) Weston on i.MX8MP sometimes produced black or grey screens. The LCDIF3 INT_STATUS_D0 register showed a FIFO underrun: 32FC6024: 1000002 The PANIC0_THRES register was set to: 32FC6238: AA0154 which apparently meant low =3D 2736 bytes (0xAA * 16 + 16), high =3D 5456 b= ytes (0x154 * 16 + 16). With this patch (based on NXP's driver) the watermarks are only 16 bytes higher (register values increased by 1) and the underruns are gone. Tested on Solidrun Hummingboard Mate with a 1080p60 HDMI display. Signed-off-by: Krzysztof Ha=C5=82asa --- a/drivers/gpu/drm/mxsfb/lcdif_kms.c +++ b/drivers/gpu/drm/mxsfb/lcdif_kms.c @@ -353,8 +353,8 @@ static void lcdif_enable_controller(struct lcdif_drm_pr= ivate *lcdif) u32 reg; =20 /* Set FIFO Panic watermarks, low 1/3, high 2/3 . */ - writel(FIELD_PREP(PANIC0_THRES_LOW_MASK, 1 * PANIC0_THRES_MAX / 3) | - FIELD_PREP(PANIC0_THRES_HIGH_MASK, 2 * PANIC0_THRES_MAX / 3), + writel(FIELD_PREP(PANIC0_THRES_LOW_MASK, DIV_ROUND_UP(1 * PANIC0_THRES_MA= X, 3)) | + FIELD_PREP(PANIC0_THRES_HIGH_MASK, DIV_ROUND_UP(2 * PANIC0_THRES_M= AX, 3)), lcdif->base + LCDC_V8_PANIC0_THRES); =20 /* --=20 Krzysztof "Chris" Ha=C5=82asa Sie=C4=87 Badawcza =C5=81ukasiewicz Przemys=C5=82owy Instytut Automatyki i Pomiar=C3=B3w PIAP Al. Jerozolimskie 202, 02-486 Warszawa