scsi: ufs-mediatek: Create reset control device_link

Mediatek UFS reset function relies on Reset Control provided by
reset-ti-syscon. To make Mediatek Reset Control work properly, select
reset-ti-syscon to ensure it is being built.

In addition, establish device_link to wait until reset-ti-syscon
initialization is complete during UFS probing.

Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Stanley Chu <[email protected]>
Signed-off-by: Peter Wang <[email protected]>
Signed-off-by: Martin K. Petersen <[email protected]>

drivers/scsi/ufs/Kconfig

@@ -115,6 +115,7 @@ config SCSI_UFS_MEDIATEK
 	tristate "Mediatek specific hooks to UFS controller platform driver"
 	depends on SCSI_UFSHCD_PLATFORM && ARCH_MEDIATEK
 	select PHY_MTK_UFS
+	select RESET_TI_SYSCON
 	help
 	  This selects the Mediatek specific additions to UFSHCD platform driver.
 	  UFS host on Mediatek needs some vendor specific configuration before

drivers/scsi/ufs/ufs-mediatek.c

@@ -1068,9 +1068,38 @@ static int ufs_mtk_probe(struct platform_device *pdev)
 {
 	int err;
 	struct device *dev = &pdev->dev;
+	struct device_node *reset_node;
+	struct platform_device *reset_pdev;
+	struct device_link *link;
+
+	reset_node = of_find_compatible_node(NULL, NULL,
+					     "ti,syscon-reset");
+	if (!reset_node) {
+		dev_notice(dev, "find ti,syscon-reset fail\n");
+		goto skip_reset;
+	}
+	reset_pdev = of_find_device_by_node(reset_node);
+	if (!reset_pdev) {
+		dev_notice(dev, "find reset_pdev fail\n");
+		goto skip_reset;
+	}
+	link = device_link_add(dev, &reset_pdev->dev,
+		DL_FLAG_AUTOPROBE_CONSUMER);
+	if (!link) {
+		dev_notice(dev, "add reset device_link fail\n");
+		goto skip_reset;
+	}
+	/* supplier is not probed */
+	if (link->status == DL_STATE_DORMANT) {
+		err = -EPROBE_DEFER;
+		goto out;
+	}
 
+skip_reset:
 	/* perform generic probe */
 	err = ufshcd_pltfrm_init(pdev, &ufs_hba_mtk_vops);
+
+out:
 	if (err)
 		dev_info(dev, "probe failed %d\n", err);