linux-kernel - [PATCH 10/10] drm/mxsfb: Clear OUTSTANDING

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Date:   Wed, 9 Jan 2019 14:13:50 +0000
From:   Robert Chiras <robert.chiras@....com>
To:     Daniel Vetter <daniel.vetter@...ll.ch>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Marek Vasut <marex@...x.de>
CC:     Robert Chiras <robert.chiras@....com>,
        Stefan Agner <stefan@...er.ch>,
        Shawn Guo <shawnguo@...nel.org>,
        Fabio Estevam <fabio.estevam@....com>,
        David Airlie <airlied@...ux.ie>,
        Anson Huang <anson.huang@....com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        dl-linux-imx <linux-imx@....com>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH 10/10] drm/mxsfb: Clear OUTSTANDING_REQS bits

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@....com>
---
 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 b9437c7..c5689c2 100644
--- a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
+++ b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
@@ -231,6 +231,13 @@ 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