s3c-fb: automatically calculate pixel clock when none is given

Add a simple algorithm which calculates the pixel clock based on the video
mode parameters.  This is only done when no pixel clock is supplied
through the platform data.

This allows drivers to omit the pixel clock data and thus share the
algorithm used for calculating it.
Signed-off-by: Maurus Cuelenaere <mcuelenaere@gmail.com>
Cc: Pawel Osciak <p.osciak@samsung.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: InKi Dae <inki.dae@samsung.com>
Cc: Ben Dooks <ben-linux@fluff.org>
Cc: Russell King <rmk@arm.linux.org.uk>
Tested-by: Donghwa Lee <yiffie9819@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/video/s3c-fb.c

@@ -1026,6 +1026,28 @@ static struct fb_ops s3c_fb_ops = {
 	.fb_ioctl	= s3c_fb_ioctl,
 };
 
+/**
+ * s3c_fb_missing_pixclock() - calculates pixel clock
+ * @mode: The video mode to change.
+ *
+ * Calculate the pixel clock when none has been given through platform data.
+ */
+static void __devinit s3c_fb_missing_pixclock(struct fb_videomode *mode)
+{
+	u64 pixclk = 1000000000000ULL;
+	u32 div;
+
+	div  = mode->left_margin + mode->hsync_len + mode->right_margin +
+	       mode->xres;
+	div *= mode->upper_margin + mode->vsync_len + mode->lower_margin +
+	       mode->yres;
+	div *= mode->refresh ? : 60;
+
+	do_div(pixclk, div);
+
+	mode->pixclock = pixclk;
+}
+
 /**
  * s3c_fb_alloc_memory() - allocate display memory for framebuffer window
  * @sfb: The base resources for the hardware.
@@ -1364,6 +1386,9 @@ static int __devinit s3c_fb_probe(struct platform_device *pdev)
 		if (!pd->win[win])
 			continue;
 
+		if (!pd->win[win]->win_mode.pixclock)
+			s3c_fb_missing_pixclock(&pd->win[win]->win_mode);
+
 		ret = s3c_fb_probe_win(sfb, win, fbdrv->win[win],
 				       &sfb->windows[win]);
 		if (ret < 0) {