fbdev: imxfb: fix left margin setting

The previous setting did not take into account the CSTN mode.
For the H_WAIT_2 bitfield (bits 0-7) of the LCDC Horizontal Configuration
Register (LCDCR), the IMX25RM manual states that:

In TFT mode, it specifies the number of SCLK periods between the end of
HSYNC and the beginning of OE signal, and the total delay time equals
(H_WAIT_2 + 3) of SCLK periods.
In CSTN mode, it specifies the number of SCLK periods between the end of
HSYNC and the first display data in each line, and the total delay time
equals (H_WAIT_2 + 2) of SCLK periods.

The patch handles both cases.

Fixes: 4e47382f ("fbdev: imxfb: warn about invalid left/right margin")
Fixes: 7e8549bc ("imxfb: Fix margin settings")
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Signed-off-by: Helge Deller <deller@gmx.de>

drivers/video/fbdev/imxfb.c

@@ -42,6 +42,7 @@
 #include <video/videomode.h>
 
 #define PCR_TFT		(1 << 31)
+#define PCR_COLOR	(1 << 30)
 #define PCR_BPIX_8	(3 << 25)
 #define PCR_BPIX_12	(4 << 25)
 #define PCR_BPIX_16	(5 << 25)
@@ -150,6 +151,12 @@ enum imxfb_type {
 	IMX21_FB,
 };
 
+enum imxfb_panel_type {
+	PANEL_TYPE_MONOCHROME,
+	PANEL_TYPE_CSTN,
+	PANEL_TYPE_TFT,
+};
+
 struct imxfb_info {
 	struct platform_device  *pdev;
 	void __iomem		*regs;
@@ -157,6 +164,7 @@ struct imxfb_info {
 	struct clk		*clk_ahb;
 	struct clk		*clk_per;
 	enum imxfb_type		devtype;
+	enum imxfb_panel_type	panel_type;
 	bool			enabled;
 
 	/*
@@ -444,6 +452,13 @@ static int imxfb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
 	if (!is_imx1_fb(fbi) && imxfb_mode->aus_mode)
 		fbi->lauscr = LAUSCR_AUS_MODE;
 
+	if (imxfb_mode->pcr & PCR_TFT)
+		fbi->panel_type = PANEL_TYPE_TFT;
+	else if (imxfb_mode->pcr & PCR_COLOR)
+		fbi->panel_type = PANEL_TYPE_CSTN;
+	else
+		fbi->panel_type = PANEL_TYPE_MONOCHROME;
+
 	/*
 	 * Copy the RGB parameters for this display
 	 * from the machine specific parameters.
@@ -596,6 +611,7 @@ static int imxfb_activate_var(struct fb_var_screeninfo *var, struct fb_info *inf
 {
 	struct imxfb_info *fbi = info->par;
 	u32 ymax_mask = is_imx1_fb(fbi) ? YMAX_MASK_IMX1 : YMAX_MASK_IMX21;
+	u8 left_margin_low;
 
 	pr_debug("var: xres=%d hslen=%d lm=%d rm=%d\n",
 		var->xres, var->hsync_len,
@@ -604,6 +620,13 @@ static int imxfb_activate_var(struct fb_var_screeninfo *var, struct fb_info *inf
 		var->yres, var->vsync_len,
 		var->upper_margin, var->lower_margin);
 
+	if (fbi->panel_type == PANEL_TYPE_TFT)
+		left_margin_low = 3;
+	else if (fbi->panel_type == PANEL_TYPE_CSTN)
+		left_margin_low = 2;
+	else
+		left_margin_low = 0;
+
 #if DEBUG_VAR
 	if (var->xres < 16        || var->xres > 1024)
 		printk(KERN_ERR "%s: invalid xres %d\n",
@@ -611,7 +634,7 @@ static int imxfb_activate_var(struct fb_var_screeninfo *var, struct fb_info *inf
 	if (var->hsync_len < 1    || var->hsync_len > 64)
 		printk(KERN_ERR "%s: invalid hsync_len %d\n",
 			info->fix.id, var->hsync_len);
-	if (var->left_margin < 3  || var->left_margin > 255)
+	if (var->left_margin < left_margin_low  || var->left_margin > 255)
 		printk(KERN_ERR "%s: invalid left_margin %d\n",
 			info->fix.id, var->left_margin);
 	if (var->right_margin < 1 || var->right_margin > 255)
@@ -637,7 +660,7 @@ static int imxfb_activate_var(struct fb_var_screeninfo *var, struct fb_info *inf
 
 	writel(HCR_H_WIDTH(var->hsync_len - 1) |
 		HCR_H_WAIT_1(var->right_margin - 1) |
-		HCR_H_WAIT_2(var->left_margin - 3),
+		HCR_H_WAIT_2(var->left_margin - left_margin_low),
 		fbi->regs + LCDC_HCR);
 
 	writel(VCR_V_WIDTH(var->vsync_len) |