drm/rockchip: dw-mipi-dsi: don't assume buffer is aligned

By dereferencing the MIPI command buffer as a u32* we rely on it being
correctly aligned on ARM, but this may not be the case.  Copy it into a
stack variable that will be correctly aligned.

Signed-off-by: John Keeping <john@metanate.com>
Reviewed-by: Chris Zhong <zyw@rock-chips.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20170224125506.21533-11-john@metanate.com

drivers/gpu/drm/rockchip/dw-mipi-dsi.c

@@ -609,10 +609,10 @@ static int dw_mipi_dsi_dcs_short_write(struct dw_mipi_dsi *dsi,
 static int dw_mipi_dsi_dcs_long_write(struct dw_mipi_dsi *dsi,
 				      const struct mipi_dsi_msg *msg)
 {
-	const u32 *tx_buf = msg->tx_buf;
-	int len = msg->tx_len, pld_data_bytes = sizeof(*tx_buf), ret;
+	const u8 *tx_buf = msg->tx_buf;
+	int len = msg->tx_len, pld_data_bytes = sizeof(u32), ret;
 	u32 hdr_val = GEN_HDATA(msg->tx_len) | GEN_HTYPE(msg->type);
-	u32 remainder = 0;
+	u32 remainder;
 	u32 val;
 
 	if (msg->tx_len < 3) {
@@ -623,12 +623,14 @@ static int dw_mipi_dsi_dcs_long_write(struct dw_mipi_dsi *dsi,
 
 	while (DIV_ROUND_UP(len, pld_data_bytes)) {
 		if (len < pld_data_bytes) {
+			remainder = 0;
 			memcpy(&remainder, tx_buf, len);
 			dsi_write(dsi, DSI_GEN_PLD_DATA, remainder);
 			len = 0;
 		} else {
-			dsi_write(dsi, DSI_GEN_PLD_DATA, *tx_buf);
-			tx_buf++;
+			memcpy(&remainder, tx_buf, pld_data_bytes);
+			dsi_write(dsi, DSI_GEN_PLD_DATA, remainder);
+			tx_buf += pld_data_bytes;
 			len -= pld_data_bytes;
 		}