Don't write to tft registers from sysfs store handler.

Writing to registers of the device directly from the sysfs store handler
leads to race conditions with updating the screen. Just set the variable
and update the scroll pos from the next update_display call.

This means the scrolling might not actually happen until you draw something
to the screen. But as scrolling without drawing a new scanline is not very
useful anyway this is a minor annoyance.

Author: Martijn Versteegh

drivers/staging/fbtft/fbtft-core.c

@@ -358,6 +358,11 @@ static void fbtft_update_display(struct fbtft_par *par, unsigned int start_line,
 		}
 	}
 
+	if (par->fbtftops.set_scroll)
+	{
+		par->fbtftops.set_scroll(par);
+	}
+
 	/* Sanity checks */
 	if (start_line > end_line) {
 		dev_warn(par->info->device,

drivers/staging/fbtft/fbtft-sysfs.c

@@ -219,8 +219,8 @@ static ssize_t store_scroll(struct device *device,
 	if (ret)
 		return ret;
 
-	if (par->fbtftops.set_scroll)
-		par->fbtftops.set_scroll(par);
+//	if (par->fbtftops.set_scroll)
+//		par->fbtftops.set_scroll(par);
 
 
 	return count;