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 5EA9ED6AAF7 for ; Thu, 2 Apr 2026 18:35:38 +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: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=eOTvAcx9xyu6MoZNJTZVQRHp0EHdMKGsrRcpN9zdBJs=; b=xpg3AM5tXK4qG+n5ygRwrRccSy MwyrEEpBRt3fJg6/CVVxY/hUOxibdDoSZyFvJBPqsLuCr5umjDpTXwJ8TZfDOsWzt8H/KEoe7J5NT macJC0s7bAIaYQZYQ9eDmO7HMgi1Y6UFhyU3qY83mQvnuFSDn4gr83FXDv0FN5AbJnp9ZsuXj/MMz K6b/TeOJByU8dGnadBBkPC7YBw/cVX94R0teVovYH9q0/mIVAWcdFG9cUN1dZDPpSixxc86vA0haZ ynw6gzJM4tpHwxrw57xObAiBYVFdU6ulp5D01JNfzkK/VfSYnzyu3WHUj+djhMfWcozkmXxNrF/1V UwlGCmTw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1w8MtA-00000000fTn-2Php; Thu, 02 Apr 2026 18:35:32 +0000 Received: from leonov.paulk.fr ([185.233.101.22]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1w8Mt7-00000000fSY-1lmz for linux-arm-kernel@lists.infradead.org; Thu, 02 Apr 2026 18:35:31 +0000 Received: from laika.paulk.fr (12.234.24.109.rev.sfr.net [109.24.234.12]) by leonov.paulk.fr (Postfix) with ESMTPS id E441B1F80041 for ; Thu, 2 Apr 2026 18:35:26 +0000 (UTC) Received: by laika.paulk.fr (Postfix, from userid 65534) id 4B5FDB40129; Thu, 2 Apr 2026 18:35:26 +0000 (UTC) Received: from shepard (unknown [192.168.1.65]) by laika.paulk.fr (Postfix) with ESMTP id 869C1B40127; Thu, 2 Apr 2026 18:33:52 +0000 (UTC) From: Paul Kocialkowski To: dri-devel@lists.freedesktop.org, imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Cc: Marek Vasut , Stefan Agner , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Frank Li , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , Lucas Stach , =?UTF-8?q?Krzysztof=20Ha=C5=82asa?= , Marco Felsch , Liu Ying , Paul Kocialkowski Subject: [PATCH v2 1/2] drm: lcdif: Set undocumented bit to clear FIFO at vsync Date: Thu, 2 Apr 2026 20:33:50 +0200 Message-ID: <20260402183351.3281123-2-paulk@sys-base.io> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260402183351.3281123-1-paulk@sys-base.io> References: <20260402183351.3281123-1-paulk@sys-base.io> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260402_113529_649762_41DD60E1 X-CRM114-Status: GOOD ( 14.54 ) 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 There is an undocumented bit used in the NXP BSP to clear the FIFO systematically at vsync. In normal operation, the FIFO should already be empty but it doesn't hurt to add it as an extra safety measure. Signed-off-by: Paul Kocialkowski Reviewed-by: Lucas Stach --- drivers/gpu/drm/mxsfb/lcdif_kms.c | 3 ++- drivers/gpu/drm/mxsfb/lcdif_regs.h | 1 + 2 files changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/mxsfb/lcdif_kms.c b/drivers/gpu/drm/mxsfb/lcdif_kms.c index ef3250a5c54f..a00c4f6d63f4 100644 --- a/drivers/gpu/drm/mxsfb/lcdif_kms.c +++ b/drivers/gpu/drm/mxsfb/lcdif_kms.c @@ -338,7 +338,8 @@ static void lcdif_set_mode(struct lcdif_drm_private *lcdif, u32 bus_flags) * Downstream set it to 256B burst size to improve the memory * efficiency so set it here too. */ - ctrl = CTRLDESCL0_3_P_SIZE(2) | CTRLDESCL0_3_T_SIZE(2) | + ctrl = CTRLDESCL0_3_STATE_CLEAR_VSYNC | + CTRLDESCL0_3_P_SIZE(2) | CTRLDESCL0_3_T_SIZE(2) | CTRLDESCL0_3_PITCH(lcdif->crtc.primary->state->fb->pitches[0]); writel(ctrl, lcdif->base + LCDC_V8_CTRLDESCL0_3); } diff --git a/drivers/gpu/drm/mxsfb/lcdif_regs.h b/drivers/gpu/drm/mxsfb/lcdif_regs.h index c55dfb236c1d..17882c593d27 100644 --- a/drivers/gpu/drm/mxsfb/lcdif_regs.h +++ b/drivers/gpu/drm/mxsfb/lcdif_regs.h @@ -190,6 +190,7 @@ #define CTRLDESCL0_1_WIDTH(n) ((n) & 0xffff) #define CTRLDESCL0_1_WIDTH_MASK GENMASK(15, 0) +#define CTRLDESCL0_3_STATE_CLEAR_VSYNC BIT(23) #define CTRLDESCL0_3_P_SIZE(n) (((n) << 20) & CTRLDESCL0_3_P_SIZE_MASK) #define CTRLDESCL0_3_P_SIZE_MASK GENMASK(22, 20) #define CTRLDESCL0_3_T_SIZE(n) (((n) << 16) & CTRLDESCL0_3_T_SIZE_MASK) -- 2.53.0