scsi: ufs: add UFS device reset support

Some platforms may have a SOC pin/gpio connected to UFS device's
RST_n to allow the UFS device reset. This change adds support to
trigger device reset on such platforms.

Change-Id: Ie4faa47fb76837dba909f9a3d0dfe11bc69659e1
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>

Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt

@@ -55,6 +55,10 @@ Optional properties:
 - lanes-per-direction:	number of lanes available per direction - either 1 or 2.
 			Note that it is assume same number of lanes is used both directions at once.
 			If not specified, default is 2 lanes per direction.
+- pinctrl-names, pinctrl-0, pinctrl-1,.. pinctrl-n: Refer to "Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt"
+			for these optional properties
+
+
 
 Note: If above properties are not defined it can be assumed that the supply
 regulators or clocks are always on.

drivers/scsi/ufs/ufshcd-pltfrm.c

@@ -250,6 +250,20 @@ static void ufshcd_parse_pm_levels(struct ufs_hba *hba)
 	}
 }
 
+static int ufshcd_parse_pinctrl_info(struct ufs_hba *hba)
+{
+	int ret = 0;
+
+	/* Try to obtain pinctrl handle */
+	hba->pctrl = devm_pinctrl_get(hba->dev);
+	if (IS_ERR(hba->pctrl)) {
+		ret = PTR_ERR(hba->pctrl);
+		hba->pctrl = NULL;
+	}
+
+	return ret;
+}
+
 #ifdef CONFIG_SMP
 /**
  * ufshcd_pltfrm_suspend - suspend power management function
@@ -361,6 +375,13 @@ int ufshcd_pltfrm_init(struct platform_device *pdev,
 		goto dealloc_host;
 	}
 
+	err = ufshcd_parse_pinctrl_info(hba);
+	if (err) {
+		dev_dbg(&pdev->dev, "%s: unable to parse pinctrl data %d\n",
+				__func__, err);
+		/* let's not fail the probe */
+	}
+
 	ufshcd_parse_pm_levels(hba);
 
 	if (!dev->dma_mask)

drivers/scsi/ufs/ufshcd.c

@@ -446,6 +446,63 @@ void ufshcd_scsi_block_requests(struct ufs_hba *hba)
 }
 EXPORT_SYMBOL(ufshcd_scsi_block_requests);
 
+static int ufshcd_device_reset_ctrl(struct ufs_hba *hba, bool ctrl)
+{
+	int ret = 0;
+
+	if (!hba->pctrl)
+		return 0;
+
+	/* Assert reset if ctrl == true */
+	if (ctrl)
+		ret = pinctrl_select_state(hba->pctrl,
+			pinctrl_lookup_state(hba->pctrl, "dev-reset-assert"));
+	else
+		ret = pinctrl_select_state(hba->pctrl,
+			pinctrl_lookup_state(hba->pctrl, "dev-reset-deassert"));
+
+	if (ret < 0)
+		dev_err(hba->dev, "%s: %s failed with err %d\n",
+			__func__, ctrl ? "Assert" : "Deassert", ret);
+
+	return ret;
+}
+
+static inline int ufshcd_assert_device_reset(struct ufs_hba *hba)
+{
+	return ufshcd_device_reset_ctrl(hba, true);
+}
+
+static inline int ufshcd_deassert_device_reset(struct ufs_hba *hba)
+{
+	return ufshcd_device_reset_ctrl(hba, false);
+}
+
+static int ufshcd_reset_device(struct ufs_hba *hba)
+{
+	int ret;
+
+	/* reset the connected UFS device */
+	ret = ufshcd_assert_device_reset(hba);
+	if (ret)
+		goto out;
+	/*
+	 * The reset signal is active low.
+	 * The UFS device shall detect more than or equal to 1us of positive
+	 * or negative RST_n pulse width.
+	 * To be on safe side, keep the reset low for atleast 10us.
+	 */
+	usleep_range(10, 15);
+
+	ret = ufshcd_deassert_device_reset(hba);
+	if (ret)
+		goto out;
+	/* same as assert, wait for atleast 10us after deassert */
+	usleep_range(10, 15);
+out:
+	return ret;
+}
+
 /* replace non-printable or non-ASCII characters with spaces */
 static inline void ufshcd_remove_non_printable(char *val)
 {
@@ -6520,6 +6577,11 @@ static int ufshcd_reset_and_restore(struct ufs_hba *hba)
 			dev_warn(hba->dev, "%s: full reset returned %d\n",
 				 __func__, err);
 
+		err = ufshcd_reset_device(hba);
+		if (err)
+			dev_warn(hba->dev, "%s: device reset failed. err %d\n",
+				 __func__, err);
+
 		err = ufshcd_host_reset_and_restore(hba);
 	} while (err && --retries);
 
@@ -9422,6 +9484,12 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
 	/* Reset controller to power on reset (POR) state */
 	ufshcd_vops_full_reset(hba);
 
+	/* reset connected UFS device */
+	err = ufshcd_reset_device(hba);
+	if (err)
+		dev_warn(hba->dev, "%s: device reset failed. err %d\n",
+			 __func__, err);
+
 	/* Host controller enable */
 	err = ufshcd_hba_enable(hba);
 	if (err) {

drivers/scsi/ufs/ufshcd.h

@@ -907,6 +907,7 @@ struct ufs_hba {
 	int scsi_block_reqs_cnt;
 
 	bool full_init_linereset;
+	struct pinctrl *pctrl;
 };
 
 static inline void ufshcd_mark_shutdown_ongoing(struct ufs_hba *hba)