drm/rockchip: cdn-dp: return error code when clk_get_rate failed

The clk_get_rate return 0 if something goes wrong, so it can never be
less then zero, the ret should be set a error code, otherwise the
cdn_dp_clk_enable will return 0 when it failed at clk_get_rate.
In addition, clk_get_rate() returns an "unsigned long", so use
"unsigned long" instead of "u32" is better.

Signed-off-by: Chris Zhong <[e-mail]>
Signed-off-by: Sean Paul <[e-mail]>
Link: http://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/rockchip/cdn-dp-core.c

···
 static int cdn_dp_clk_enable(struct cdn_dp_device *dp)
 {
 	int ret;
-	u32 rate;
+	unsigned long rate;
 
 	ret = clk_prepare_enable(dp->pclk);
 	if (ret < 0) {
···
 
 	rate = clk_get_rate(dp->core_clk);
 	if (!rate) {
-		DRM_DEV_ERROR(dp->dev, "get clk rate failed: %d\n", rate);
+		DRM_DEV_ERROR(dp->dev, "get clk rate failed\n");
+		ret = -EINVAL;
 		goto err_set_rate;
 	}
 

drivers/gpu/drm/rockchip/cdn-dp-reg.c

···
 #define LINK_TRAINING_RETRY_MS		20
 #define LINK_TRAINING_TIMEOUT_MS	500
 
-void cdn_dp_set_fw_clk(struct cdn_dp_device *dp, u32 clk)
+void cdn_dp_set_fw_clk(struct cdn_dp_device *dp, unsigned long clk)
 {
 	writel(clk / 1000000, dp->regs + SW_CLK_H);
 }

drivers/gpu/drm/rockchip/cdn-dp-reg.h

···
 
 void cdn_dp_clock_reset(struct cdn_dp_device *dp);
 
-void cdn_dp_set_fw_clk(struct cdn_dp_device *dp, u32 clk);
+void cdn_dp_set_fw_clk(struct cdn_dp_device *dp, unsigned long clk);
 int cdn_dp_load_firmware(struct cdn_dp_device *dp, const u32 *i_mem,
 			 u32 i_size, const u32 *d_mem, u32 d_size);
 int cdn_dp_set_firmware_active(struct cdn_dp_device *dp, bool enable);