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From:   Robert Chiras <robert.chiras@nxp.com>
To:     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,
        Robert Chiras <robert.chiras@nxp.com>
Subject: [PATCH 09/10] drm/mxsfb: Clear OUTSTANDING_REQS bits
Date:   Wed, 26 Jun 2019 16:32:17 +0300
Message-Id: <1561555938-21595-10-git-send-email-robert.chiras@nxp.com>
In-Reply-To: <1561555938-21595-1-git-send-email-robert.chiras@nxp.com>
References: <1561555938-21595-1-git-send-email-robert.chiras@nxp.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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>
---
 drivers/gpu/drm/mxsfb/mxsfb_crtc.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
index 45ca16b..02a5684 100644
--- a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
+++ b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
@@ -223,7 +223,14 @@ static void mxsfb_enable_controller(struct mxsfb_drm_private *mxsfb)
 	clk_prepare_enable(mxsfb->clk);
 
 	if (mxsfb->devdata->ipversion >= 4) {
-		writel(CTRL2_OUTSTANDING_REQS__REQ_16,
+		/*
+		 * 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 */
 		writel(CTRL2_LCD_RESET, mxsfb->base + LCDC_V4_CTRL2 + REG_SET);
-- 
2.7.4