Re: [PATCH v2] video: mxsfb: Make sure axi clock is enabled when accessing registers

from memory.  This patch makes sure the axi clock is enabled when accessing
registers so that the kernel hang up issue can be fixed.

Reported-by: Peter Chen <redacted>
Tested-by: Peter Chen <redacted>
Cc: <redacted> # 3.19+
Signed-off-by: Liu Ying <redacted>
---
v1->v2:
* Add 'Tested-by: Peter Chen [off-list ref]' tag.
* Add 'Cc: [off-list ref] # 3.19+' tag.

 drivers/video/fbdev/mxsfb.c | 70 ++++++++++++++++++++++++++++++++++++---------
 1 file changed, 56 insertions(+), 14 deletions(-)

diff --git a/drivers/video/fbdev/mxsfb.c b/drivers/video/fbdev/mxsfb.c
index f8ac4a4..a8cf3b2 100644
--- a/drivers/video/fbdev/mxsfb.c
+++ b/drivers/video/fbdev/mxsfb.c

@@ -316,6 +316,18 @@ static int mxsfb_check_var(struct fb_var_screeninfo *var,
 	return 0;
 }
 
+static inline void mxsfb_enable_axi_clk(struct mxsfb_info *host)
+{
+	if (host->clk_axi)
+		clk_prepare_enable(host->clk_axi);
+}
+
+static inline void mxsfb_disable_axi_clk(struct mxsfb_info *host)
+{
+	if (host->clk_axi)
+		clk_disable_unprepare(host->clk_axi);
+}
+
 static void mxsfb_enable_controller(struct fb_info *fb_info)
 {
 	struct mxsfb_info *host = to_imxfb_host(fb_info);

@@ -333,14 +345,13 @@ static void mxsfb_enable_controller(struct fb_info *fb_info)
 		}
 	}
 
-	if (host->clk_axi)
-		clk_prepare_enable(host->clk_axi);
-
 	if (host->clk_disp_axi)
 		clk_prepare_enable(host->clk_disp_axi);
 	clk_prepare_enable(host->clk);
 	clk_set_rate(host->clk, PICOS2KHZ(fb_info->var.pixclock) * 1000U);
 
+	mxsfb_enable_axi_clk(host);
+

 	/* if it was disabled, re-enable the mode again */
 	writel(CTRL_DOTCLK_MODE, host->base + LCDC_CTRL + REG_SET);
 

@@ -380,11 +391,11 @@ static void mxsfb_disable_controller(struct fb_info *fb_info)
 	reg = readl(host->base + LCDC_VDCTRL4);
 	writel(reg & ~VDCTRL4_SYNC_SIGNALS_ON, host->base + LCDC_VDCTRL4);
 
+	mxsfb_disable_axi_clk(host);
+
 	clk_disable_unprepare(host->clk);
 	if (host->clk_disp_axi)
 		clk_disable_unprepare(host->clk_disp_axi);
-	if (host->clk_axi)
-		clk_disable_unprepare(host->clk_axi);

 	host->enabled = 0;
 

@@ -421,6 +432,8 @@ static int mxsfb_set_par(struct fb_info *fb_info)
 		mxsfb_disable_controller(fb_info);
 	}
 
+	mxsfb_enable_axi_clk(host);
+
 	/* clear the FIFOs */
 	writel(CTRL1_FIFO_CLEAR, host->base + LCDC_CTRL1 + REG_SET);
 

@@ -438,6 +451,7 @@ static int mxsfb_set_par(struct fb_info *fb_info)
 		ctrl |= CTRL_SET_WORD_LENGTH(3);
 		switch (host->ld_intf_width) {
 		case STMLCDIF_8BIT:
+			mxsfb_disable_axi_clk(host);
 			dev_err(&host->pdev->dev,
 					"Unsupported LCD bus width mapping\n");
 			return -EINVAL;

@@ -451,6 +465,7 @@ static int mxsfb_set_par(struct fb_info *fb_info)
 		writel(CTRL1_SET_BYTE_PACKAGING(0x7), host->base + LCDC_CTRL1);
 		break;
 	default:
+		mxsfb_disable_axi_clk(host);
 		dev_err(&host->pdev->dev, "Unhandled color depth of %u\n",
 				fb_info->var.bits_per_pixel);
 		return -EINVAL;

@@ -504,6 +519,8 @@ static int mxsfb_set_par(struct fb_info *fb_info)
 			fb_info->fix.line_length * fb_info->var.yoffset,
 			host->base + host->devdata->next_buf);
 
+	mxsfb_disable_axi_clk(host);
+
 	if (reenable)
 		mxsfb_enable_controller(fb_info);
 

@@ -582,10 +599,16 @@ static int mxsfb_pan_display(struct fb_var_screeninfo *var,
 
 	offset = fb_info->fix.line_length * var->yoffset;
 
+	if (!host->enabled)
+		mxsfb_enable_axi_clk(host);
+
 	/* update on next VSYNC */
 	writel(fb_info->fix.smem_start + offset,
 			host->base + host->devdata->next_buf);
 
+	if (!host->enabled)
+		mxsfb_disable_axi_clk(host);
+