Fix memory region in framebuffer and cache synchronization

backend/fbdev.c

@@ -20,6 +20,7 @@
 
 #define FBDEV_NAME "FRAMEBUFFER"
 #define FBDEV_DEFAULT "/dev/fb0"
+#define FBIO_CACHE_SYNC 0x4630
 #define SCREEN(x) ((twin_context_t *) x)->screen
 #define PRIV(x) ((twin_fbdev_t *) ((twin_context_t *) x)->priv)
 
@@ -56,12 +57,23 @@ static void _twin_fbdev_put_span(twin_coord_t left,
         return;
 
     twin_coord_t width = right - left;
-    off_t off = top * screen->width + left;
-    uint32_t *dest =
-        (uint32_t *) ((uintptr_t) tx->fb_base + (off * sizeof(uint32_t)));
+    off_t off = tx->fb_fix.line_length * top + 4 * left;
+    unsigned char *dest = (unsigned char *) tx->fb_base + off;
     memcpy(dest, pixels, width * sizeof(uint32_t));
 }
 
+static void twin_fbdev_cache_sync(void *closure)
+{
+    twin_fbdev_t *tx = PRIV(closure);
+    unsigned int args[2];
+    args[0] = tx->fb_base;
+    args[1] = tx->fb_base + tx->fb_var.yres_virtual * tx->fb_fix.line_length;
+    ioctl(tx->fb_fd, FBIO_CACHE_SYNC, args);
+
+    struct fb_var_screeninfo var = tx->fb_var;
+    ioctl(tx->fb_fd, FBIOPAN_DISPLAY, &var);
+}
+
 static void twin_fbdev_get_screen_size(twin_fbdev_t *tx,
                                        int *width,
                                        int *height)
@@ -85,6 +97,7 @@ static bool twin_fbdev_work(void *closure)
 
     if (twin_screen_damaged(screen))
         twin_screen_update(screen);
+    twin_fbdev_cache_sync(closure);
     return true;
 }