[PATCH 3/4] [ARM] s3c-fb: Add support for display panning

@@ -294,6 +294,8 @@ static int s3c_fb_set_par(struct fb_info *info)
 	}
 
 	info->fix.line_length = (var->xres_virtual * var->bits_per_pixel) / 8;
+	info->fix.xpanstep = info->var.xres_virtual > info->var.xres ? 1 : 0;
+	info->fix.ypanstep = info->var.yres_virtual > info->var.yres ? 1 : 0;
 
 	/* disable the window whilst we update it */
 	writel(0, regs + WINCON(win_no));

@@ -640,6 +642,38 @@ static int s3c_fb_blank(int blank_mode, struct fb_info *info)
 	return 0;
 }
 
+/**
+ * s3c_fb_pan_display() - Pan the display.
+ *
+ * Note, that the offsets can be written to the device at any time, as their
+ * values are latched at each vsync automatically. This also means that only
+ * the last call to this function will have any effect on next vsync, but
+ * there is no need to sleep waiting for it to prevent tearing.
+ *
+ * @var: The screen information to verify.
+ * @info: The framebuffer device.
+ */
+static int s3c_fb_pan_display(struct fb_var_screeninfo *var,
+			      struct fb_info *info)
+{
+	struct s3c_fb_win *win	= info->par;
+	struct s3c_fb *sfb	= win->parent;
+	unsigned int start_byte_offset, end_byte_offset;
+
+	/* Offset in bytes to the start of the displayed area */
+	start_byte_offset = var->yoffset * info->fix.line_length
+			    + var->xoffset * (info->var.bits_per_pixel) / 8;
+	writel(info->fix.smem_start + start_byte_offset,
+	       sfb->regs + VIDW_BUF_START(win->index));
+
+	/* Offset in bytes to the end of the displayed area */
+	end_byte_offset = start_byte_offset + var->yres * info->fix.line_length;
+	writel(info->fix.smem_start + end_byte_offset,
+	       sfb->regs + VIDW_BUF_END(win->index));
+
+	return 0;
+}
+
 static struct fb_ops s3c_fb_ops = {
 	.owner		= THIS_MODULE,
 	.fb_check_var	= s3c_fb_check_var,

@@ -649,6 +683,7 @@ static struct fb_ops s3c_fb_ops = {
 	.fb_fillrect	= cfb_fillrect,
 	.fb_copyarea	= cfb_copyarea,
 	.fb_imageblit	= cfb_imageblit,
+	.fb_pan_display	= s3c_fb_pan_display,
 };
 
 /**

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