[PATCH 4/5] phy: mediatek: ufs: Add support for resets

[Nicolas Frattaroli <nicolas.frattaroli@collabora.com>]

The MediaTek UFS PHY supports PHY resets. Until now, they've been
implemented in the UFS host driver. Since they were never documented in
the UFS HCI node's DT bindings, and no mainline DT uses it, it's fine if
it's moved to the correct location, which is the PHY driver.

Implement the MPHY reset logic in this driver and expose it through the
phy subsystem's reset op. The reset itself is optional, as judging by
other mainline devices that use this hardware, it's not required for the
device to function.

If no reset is present, the reset op returns -EOPNOTSUPP, which means
that the ufshci driver can detect it's present and not double sleep in
its own reset function, where it will call the phy reset.

Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
---
 drivers/phy/mediatek/phy-mtk-ufs.c | 71 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)

diff --git a/drivers/phy/mediatek/phy-mtk-ufs.c b/drivers/phy/mediatek/phy-mtk-ufs.c
index 0cb5a25b1b7a..d77ba689ebc8 100644
--- a/drivers/phy/mediatek/phy-mtk-ufs.c
+++ b/drivers/phy/mediatek/phy-mtk-ufs.c
@@ -4,6 +4,7 @@
  * Author: Stanley Chu <stanley.chu@mediatek.com>
  */
 
+#include <linux/arm-smccc.h>
 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/io.h>
@@ -11,6 +12,8 @@
 #include <linux/module.h>
 #include <linux/phy/phy.h>
 #include <linux/platform_device.h>
+#include <linux/reset.h>
+#include <linux/soc/mediatek/mtk_sip_svc.h>
 
 #include "phy-mtk-io.h"
 
@@ -36,9 +39,17 @@
 
 #define UFSPHY_CLKS_CNT    2
 
+#define UFS_MTK_SIP_MPHY_CTRL       BIT(8)
+
+enum ufs_mtk_mphy_op {
+	UFS_MPHY_BACKUP = 0,
+	UFS_MPHY_RESTORE
+};
+
 struct ufs_mtk_phy {
 	struct device *dev;
 	void __iomem *mmio;
+	struct reset_control *reset;
 	struct clk_bulk_data clks[UFSPHY_CLKS_CNT];
 };
 
@@ -141,9 +152,59 @@ static int ufs_mtk_phy_power_off(struct phy *generic_phy)
 	return 0;
 }
 
+static int ufs_mtk_phy_ctrl(struct ufs_mtk_phy *phy, enum ufs_mtk_mphy_op op)
+{
+	struct arm_smccc_res res;
+
+	arm_smccc_smc(MTK_SIP_UFS_CONTROL, UFS_MTK_SIP_MPHY_CTRL, op,
+		      0, 0, 0, 0, 0, &res);
+
+	switch (res.a0) {
+	case SMCCC_RET_NOT_SUPPORTED:
+		return -EOPNOTSUPP;
+	case SMCCC_RET_INVALID_PARAMETER:
+		return -EINVAL;
+	default:
+		return 0;
+	}
+}
+
+static int ufs_mtk_phy_reset(struct phy *generic_phy)
+{
+	struct ufs_mtk_phy *phy = get_ufs_mtk_phy(generic_phy);
+	int ret;
+
+	if (!phy->reset)
+		return -EOPNOTSUPP;
+
+	ret = reset_control_assert(phy->reset);
+	if (ret)
+		return ret;
+
+	usleep_range(100, 110);
+
+	ret = reset_control_deassert(phy->reset);
+	if (ret)
+		return ret;
+
+	/*
+	 * To avoid double-sleep and other unintended side-effects in the ufshci
+	 * driver, don't return the phy_ctrl retval here, but just return -EPROTO.
+	 */
+	ret = ufs_mtk_phy_ctrl(phy, UFS_MPHY_RESTORE);
+	if (ret) {
+		dev_err(phy->dev, "UFS_MPHY_RESTORE SMC command failed: %pe\n",
+			ERR_PTR(ret));
+		return -EPROTO;
+	}
+
+	return 0;
+}
+
 static const struct phy_ops ufs_mtk_phy_ops = {
 	.power_on       = ufs_mtk_phy_power_on,
 	.power_off      = ufs_mtk_phy_power_off,
+	.reset          = ufs_mtk_phy_reset,
 	.owner          = THIS_MODULE,
 };
 
@@ -163,8 +224,18 @@ static int ufs_mtk_phy_probe(struct platform_device *pdev)
 	if (IS_ERR(phy->mmio))
 		return PTR_ERR(phy->mmio);
 
+	phy->reset = devm_reset_control_get_optional(dev, NULL);
+	if (IS_ERR(phy->reset))
+		return dev_err_probe(dev, PTR_ERR(phy->reset), "Failed to get reset\n");
+
 	phy->dev = dev;
 
+	if (phy->reset) {
+		ret = ufs_mtk_phy_ctrl(phy, UFS_MPHY_BACKUP);
+		if (ret)
+			return dev_err_probe(dev, ret, "Failed to back up MPHY\n");
+	}
+
 	ret = ufs_mtk_phy_clk_init(phy);
 	if (ret)
 		return ret;

-- 
2.51.0