[PATCH v1 3/6] scsi: ufs-mediatek: introduce reference clock control

[Stanley Chu]

Introduce reference clock control in MediaTek Chipset in order
to disable it if it is not necessary by UFS device to save system power.

Currently reference clock can be disabled during system suspend, runtime
suspend and clock-gating after link enters hibernate state.

Signed-off-by: Stanley Chu <stanley.chu@xxxxxxxxxxxx>
Reviewed-by: Alim Akhtar <alim.akhtar@xxxxxxxxxxx>
---
 drivers/scsi/ufs/ufs-mediatek.c | 64 ++++++++++++++++++++++++++++++---
 drivers/scsi/ufs/ufs-mediatek.h | 20 +++++++++--
 2 files changed, 78 insertions(+), 6 deletions(-)

diff --git a/drivers/scsi/ufs/ufs-mediatek.c b/drivers/scsi/ufs/ufs-mediatek.c
index 6a3ec11b16db..690483c78212 100644
--- a/drivers/scsi/ufs/ufs-mediatek.c
+++ b/drivers/scsi/ufs/ufs-mediatek.c
@@ -18,6 +18,11 @@
 #include "unipro.h"
 #include "ufs-mediatek.h"
 
+#define ufs_mtk_ref_clk_notify(on, res) \
+	arm_smccc_smc(MTK_SIP_UFS_CONTROL, \
+		      UFS_MTK_SIP_REF_CLK_NOTIFICATION, \
+		      on, 0, 0, 0, 0, 0, &(res))
+
 static void ufs_mtk_cfg_unipro_cg(struct ufs_hba *hba, bool enable)
 {
 	u32 tmp;
@@ -83,6 +88,49 @@ static int ufs_mtk_bind_mphy(struct ufs_hba *hba)
 	return err;
 }
 
+static int ufs_mtk_setup_ref_clk(struct ufs_hba *hba, bool on)
+{
+	struct ufs_mtk_host *host = ufshcd_get_variant(hba);
+	struct arm_smccc_res res;
+	unsigned long timeout;
+	u32 value;
+
+	if (host->ref_clk_enabled == on)
+		return 0;
+
+	if (on) {
+		ufs_mtk_ref_clk_notify(on, res);
+		ufshcd_writel(hba, REFCLK_REQUEST, REG_UFS_REFCLK_CTRL);
+	} else {
+		ufshcd_writel(hba, REFCLK_RELEASE, REG_UFS_REFCLK_CTRL);
+	}
+
+	/* Wait for ack */
+	timeout = jiffies + msecs_to_jiffies(REFCLK_REQ_TIMEOUT_MS);
+	do {
+		value = ufshcd_readl(hba, REG_UFS_REFCLK_CTRL);
+
+		/* Wait until ack bit equals to req bit */
+		if (((value & REFCLK_ACK) >> 1) == (value & REFCLK_REQUEST))
+			goto out;
+
+		usleep_range(100, 200);
+	} while (time_before(jiffies, timeout));
+
+	dev_err(hba->dev, "missing ack of refclk req, reg: 0x%x\n", value);
+
+	ufs_mtk_ref_clk_notify(host->ref_clk_enabled, res);
+
+	return -ETIMEDOUT;
+
+out:
+	host->ref_clk_enabled = on;
+	if (!on)
+		ufs_mtk_ref_clk_notify(on, res);
+
+	return 0;
+}
+
 /**
  * ufs_mtk_setup_clocks - enables/disable clocks
  * @hba: host controller instance
@@ -107,12 +155,16 @@ static int ufs_mtk_setup_clocks(struct ufs_hba *hba, bool on,
 
 	switch (status) {
 	case PRE_CHANGE:
-		if (!on)
+		if (!on) {
+			ufs_mtk_setup_ref_clk(hba, on);
 			ret = phy_power_off(host->mphy);
+		}
 		break;
 	case POST_CHANGE:
-		if (on)
+		if (on) {
 			ret = phy_power_on(host->mphy);
+			ufs_mtk_setup_ref_clk(hba, on);
+		}
 		break;
 	}
 
@@ -299,8 +351,10 @@ static int ufs_mtk_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 {
 	struct ufs_mtk_host *host = ufshcd_get_variant(hba);
 
-	if (ufshcd_is_link_hibern8(hba))
+	if (ufshcd_is_link_hibern8(hba)) {
 		phy_power_off(host->mphy);
+		ufs_mtk_setup_ref_clk(hba, false);
+	}
 
 	return 0;
 }
@@ -309,8 +363,10 @@ static int ufs_mtk_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 {
 	struct ufs_mtk_host *host = ufshcd_get_variant(hba);
 
-	if (ufshcd_is_link_hibern8(hba))
+	if (ufshcd_is_link_hibern8(hba)) {
+		ufs_mtk_setup_ref_clk(hba, true);
 		phy_power_on(host->mphy);
+	}
 
 	return 0;
 }
diff --git a/drivers/scsi/ufs/ufs-mediatek.h b/drivers/scsi/ufs/ufs-mediatek.h
index b03f601d3a9e..14f8a8357c09 100644
--- a/drivers/scsi/ufs/ufs-mediatek.h
+++ b/drivers/scsi/ufs/ufs-mediatek.h
@@ -6,7 +6,21 @@
 #ifndef _UFS_MEDIATEK_H
 #define _UFS_MEDIATEK_H
 
-#include <linux/bitops.h>
+/*
+ * Vendor specific UFSHCI Registers
+ */
+#define REG_UFS_REFCLK_CTRL         0x144
+
+/*
+ * Ref-clk control
+ *
+ * Values for register REG_UFS_REFCLK_CTRL
+ */
+#define REFCLK_RELEASE              0x0
+#define REFCLK_REQUEST              BIT(0)
+#define REFCLK_ACK                  BIT(1)
+
+#define REFCLK_REQ_TIMEOUT_MS       3
 
 /*
  * Vendor specific pre-defined parameters
@@ -34,7 +48,8 @@
 /*
  * SiP commands
  */
-#define UFS_MTK_SIP_DEVICE_RESET    BIT(1)
+#define UFS_MTK_SIP_DEVICE_RESET          BIT(1)
+#define UFS_MTK_SIP_REF_CLK_NOTIFICATION  BIT(3)
 
 /*
  * VS_DEBUGCLOCKENABLE
@@ -55,6 +70,7 @@ enum {
 struct ufs_mtk_host {
 	struct ufs_hba *hba;
 	struct phy *mphy;
+	bool ref_clk_enabled;
 };
 
 #endif /* !_UFS_MEDIATEK_H */
-- 
2.18.0