drm/simpledrm: Compute framebuffer stride if not set

Compute the framebuffer's scanline stride length if not given by
the simplefb data.

v3:
	* get pixel size from drm_format_info_bpp() (Geert, Javier)

Signed-off-by: Thomas Zimmermann <[email protected]>
Acked-by: Javier Martinez Canillas <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

drivers/gpu/drm/tiny/simpledrm.c

@@ -743,6 +743,9 @@ static struct simpledrm_device *simpledrm_device_create(struct drm_driver *drv,
 		drm_err(dev, "no simplefb configuration found\n");
 		return ERR_PTR(-ENODEV);
 	}
+	if (!stride)
+		stride = DIV_ROUND_UP(drm_format_info_bpp(format, 0) * width, 8);
+
 	sdev->mode = simpledrm_mode(width, height);
 	sdev->format = format;
 	sdev->pitch = stride;