linux-kernel - [PATCH 4.11 11/78] drm: mxsfb_crtc: Reset the eLCDIF controller

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Date:   Mon, 19 Jun 2017 23:15:11 +0800
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Fabio Estevam <fabio.estevam@....com>,
        Sean Paul <seanpaul@...omium.org>
Subject: [PATCH 4.11 11/78] drm: mxsfb_crtc: Reset the eLCDIF controller

4.11-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Fabio Estevam <fabio.estevam@....com>

commit 0f933328f018c118ded2035f12068bbdfdef399d upstream.

According to the eLCDIF initialization steps listed in the MX6SX
Reference Manual the eLCDIF block reset is mandatory.

Without performing the eLCDIF reset the display shows garbage content
when the kernel boots.

In earlier tests this issue has not been observed because the bootloader
was previously showing a splash screen and the bootloader display driver
does properly implement the eLCDIF reset.

Add the eLCDIF reset to the driver, so that it can operate correctly
independently of the bootloader.

Tested on a imx6sx-sdb board.

Signed-off-by: Fabio Estevam <fabio.estevam@....com>
Signed-off-by: Sean Paul <seanpaul@...omium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1494007301-14535-1-git-send-email-fabio.estevam@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/mxsfb/mxsfb_crtc.c |   42 +++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

--- a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
+++ b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
@@ -35,6 +35,13 @@
 #include "mxsfb_drv.h"
 #include "mxsfb_regs.h"
 
+#define MXS_SET_ADDR		0x4
+#define MXS_CLR_ADDR		0x8
+#define MODULE_CLKGATE		BIT(30)
+#define MODULE_SFTRST		BIT(31)
+/* 1 second delay should be plenty of time for block reset */
+#define RESET_TIMEOUT		1000000
+
 static u32 set_hsync_pulse_width(struct mxsfb_drm_private *mxsfb, u32 val)
 {
 	return (val & mxsfb->devdata->hs_wdth_mask) <<
@@ -159,6 +166,36 @@ static void mxsfb_disable_controller(str
 		clk_disable_unprepare(mxsfb->clk_disp_axi);
 }
 
+/*
+ * Clear the bit and poll it cleared.  This is usually called with
+ * a reset address and mask being either SFTRST(bit 31) or CLKGATE
+ * (bit 30).
+ */
+static int clear_poll_bit(void __iomem *addr, u32 mask)
+{
+	u32 reg;
+
+	writel(mask, addr + MXS_CLR_ADDR);
+	return readl_poll_timeout(addr, reg, !(reg & mask), 0, RESET_TIMEOUT);
+}
+
+static int mxsfb_reset_block(void __iomem *reset_addr)
+{
+	int ret;
+
+	ret = clear_poll_bit(reset_addr, MODULE_SFTRST);
+	if (ret)
+		return ret;
+
+	writel(MODULE_CLKGATE, reset_addr + MXS_CLR_ADDR);
+
+	ret = clear_poll_bit(reset_addr, MODULE_SFTRST);
+	if (ret)
+		return ret;
+
+	return clear_poll_bit(reset_addr, MODULE_CLKGATE);
+}
+
 static void mxsfb_crtc_mode_set_nofb(struct mxsfb_drm_private *mxsfb)
 {
 	struct drm_display_mode *m = &mxsfb->pipe.crtc.state->adjusted_mode;
@@ -173,6 +210,11 @@ static void mxsfb_crtc_mode_set_nofb(str
 	 */
 	mxsfb_enable_axi_clk(mxsfb);
 
+	/* Mandatory eLCDIF reset as per the Reference Manual */
+	err = mxsfb_reset_block(mxsfb->base);
+	if (err)
+		return;
+
 	/* Clear the FIFOs */
 	writel(CTRL1_FIFO_CLEAR, mxsfb->base + LCDC_CTRL1 + REG_SET);