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From:   Robert Chiras <robert.chiras@nxp.com>
To:     =?UTF-8?q?Guido=20G=C3=BCnther?= <agx@sigxcpu.org>,
        Marek Vasut <marex@denx.de>, Stefan Agner <stefan@agner.ch>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Shawn Guo <shawnguo@kernel.org>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Fabio Estevam <festevam@gmail.com>
Cc:     Pengutronix Kernel Team <kernel@pengutronix.de>,
        NXP Linux Team <linux-imx@nxp.com>,
        dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: [PATCH v4 12/14] drm/mxsfb: Clear OUTSTANDING_REQS bits
Date:   Thu, 29 Aug 2019 14:30:13 +0300
Message-Id: <1567078215-31601-13-git-send-email-robert.chiras@nxp.com>
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Bit 21 can alter the CTRL2_OUTSTANDING_REQS value right after the eLCDIF
is enabled, since it comes up with default value of 1 (this behaviour
has been seen on some imx8 platforms).
In order to fix this, clear CTRL2_OUTSTANDING_REQS bits before setting
its value.

Signed-off-by: Robert Chiras <robert.chiras@nxp.com>
Tested-by: Guido Günther <agx@sigxcpu.org>
---
 drivers/gpu/drm/mxsfb/mxsfb_crtc.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
index e727f5e..a12f53d 100644
--- a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
+++ b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
@@ -225,6 +225,13 @@ static void mxsfb_enable_controller(struct mxsfb_drm_private *mxsfb)
 	clk_prepare_enable(mxsfb->clk);
 
 	if (mxsfb->devdata->ipversion >= 4) {
+		/*
+		 * On some platforms, bit 21 is defaulted to 1, which may alter
+		 * the below setting. So, to make sure we have the right setting
+		 * clear all the bits for CTRL2_OUTSTANDING_REQS.
+		 */
+		writel(CTRL2_OUTSTANDING_REQS(0x7),
+		       mxsfb->base + LCDC_V4_CTRL2 + REG_CLR);
 		writel(CTRL2_OUTSTANDING_REQS(REQ_16),
 		       mxsfb->base + LCDC_V4_CTRL2 + REG_SET);
 		/* Assert LCD Reset bit */
-- 
2.7.4