drm/mediatek: fix a timeout loop

This code causes a static checker warning because it treats "i == 0" as
a timeout but, because it's a post-op, the loop actually ends with "i"
set to -1.  Philipp Zabel points out that it would be cleaner to use
readl_poll_timeout() instead.

Fixes: 21898816831f ("drm/mediatek: add dsi transfer function")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: CK Hu <ck.hu@mediatek.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>

diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
index 808b995..b5cc6e1 100644 (file)
--- a/drivers/gpu/drm/mediatek/mtk_dsi.c
+++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
@@ -19,6 +19,7 @@
 #include <drm/drm_of.h>
 #include <linux/clk.h>
 #include <linux/component.h>
+#include <linux/iopoll.h>
 #include <linux/irq.h>
 #include <linux/of.h>
 #include <linux/of_platform.h>
@@ -900,16 +901,12 @@ static int mtk_dsi_host_detach(struct mipi_dsi_host *host,
 
 static void mtk_dsi_wait_for_idle(struct mtk_dsi *dsi)
 {
-       u32 timeout_ms = 500000; /* total 1s ~ 2s timeout */
-
-       while (timeout_ms--) {
-               if (!(readl(dsi->regs + DSI_INTSTA) & DSI_BUSY))
-                       break;
-
-               usleep_range(2, 4);
-       }
+       int ret;
+       u32 val;
 
-       if (timeout_ms == 0) {
+       ret = readl_poll_timeout(dsi->regs + DSI_INTSTA, val, !(val & DSI_BUSY),
+                                4, 2000000);
+       if (ret) {
                DRM_WARN("polling dsi wait not busy timeout!\n");
 
                mtk_dsi_enable(dsi);