[media] v4l: atmel-isi: Make the MCK clock optional

ISI_MCK is the sensor master clock. It should be handled by the sensor
driver directly, as the ISI has no use for that clock. Make the clock
optional here while platforms transition to the correct model.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Josh Wu <josh.wu@atmel.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

drivers/media/platform/soc_camera/atmel-isi.c

@@ -725,11 +725,13 @@ static int isi_camera_clock_start(struct soc_camera_host *ici)
 	if (ret)
 		return ret;
 
+	if (!IS_ERR(isi->mck)) {
 		ret = clk_prepare_enable(isi->mck);
 		if (ret) {
 			clk_disable_unprepare(isi->pclk);
 			return ret;
 		}
+	}
 
 	return 0;
 }
@@ -739,6 +741,7 @@ static void isi_camera_clock_stop(struct soc_camera_host *ici)
 {
 	struct atmel_isi *isi = ici->priv;
 
+	if (!IS_ERR(isi->mck))
 		clk_disable_unprepare(isi->mck);
 	clk_disable_unprepare(isi->pclk);
 }
@@ -883,7 +886,7 @@ static int atmel_isi_probe(struct platform_device *pdev)
 	struct isi_platform_data *pdata;
 
 	pdata = dev->platform_data;
-	if (!pdata || !pdata->data_width_flags || !pdata->mck_hz) {
+	if (!pdata || !pdata->data_width_flags) {
 		dev_err(&pdev->dev,
 			"No config available for Atmel ISI\n");
 		return -EINVAL;
@@ -905,17 +908,20 @@ static int atmel_isi_probe(struct platform_device *pdev)
 	INIT_LIST_HEAD(&isi->video_buffer_list);
 	INIT_LIST_HEAD(&isi->dma_desc_head);
 
-	/* Get ISI_MCK, provided by programmable clock or external clock */
+	/* ISI_MCK is the sensor master clock. It should be handled by the
+	 * sensor driver directly, as the ISI has no use for that clock. Make
+	 * the clock optional here while platforms transition to the correct
+	 * model.
+	 */
 	isi->mck = devm_clk_get(dev, "isi_mck");
-	if (IS_ERR(isi->mck)) {
-		dev_err(dev, "Failed to get isi_mck\n");
-		return PTR_ERR(isi->mck);
-	}
-
-	/* Set ISI_MCK's frequency, it should be faster than pixel clock */
+	if (!IS_ERR(isi->mck)) {
+		/* Set ISI_MCK's frequency, it should be faster than pixel
+		 * clock.
+		 */
 		ret = clk_set_rate(isi->mck, pdata->mck_hz);
 		if (ret < 0)
 			return ret;
+	}
 
 	isi->p_fb_descriptors = dma_alloc_coherent(&pdev->dev,
 				sizeof(struct fbd) * MAX_BUFFER_NUM,