scsi: ufs-mediatek: introduce reference clock control

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.

Cc: Alim Akhtar <alim.akhtar@samsung.com>
Cc: Avri Altman <avri.altman@wdc.com>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Bean Huo <beanhuo@micron.com>
Cc: Can Guo <cang@codeaurora.org>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Link: https://lore.kernel.org/r/1577683950-1702-4-git-send-email-stanley.chu@mediatek.comReviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/ufs/ufs-mediatek.c

@@ -22,6 +22,9 @@
 	arm_smccc_smc(MTK_SIP_UFS_CONTROL, \
 		      cmd, val, 0, 0, 0, 0, 0, &(res))
 
+#define ufs_mtk_ref_clk_notify(on, res) \
+	ufs_mtk_smc(UFS_MTK_SIP_REF_CLK_NOTIFICATION, on, res)
+
 #define ufs_mtk_device_reset_ctrl(high, res) \
 	ufs_mtk_smc(UFS_MTK_SIP_DEVICE_RESET, high, res)
 
@@ -90,6 +93,49 @@ 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
@@ -114,12 +160,16 @@ 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;
 	}
 
@@ -305,8 +355,10 @@ 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;
 }
@@ -315,8 +367,10 @@ 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;
 }

drivers/scsi/ufs/ufs-mediatek.h

@@ -9,6 +9,22 @@
 #include <linux/bitops.h>
 #include <linux/soc/mediatek/mtk_sip_svc.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
  */
@@ -35,8 +51,9 @@
 /*
  * SiP commands
  */
-#define MTK_SIP_UFS_CONTROL         MTK_SIP_SMC_CMD(0x276)
-#define UFS_MTK_SIP_DEVICE_RESET    BIT(1)
+#define MTK_SIP_UFS_CONTROL               MTK_SIP_SMC_CMD(0x276)
+#define UFS_MTK_SIP_DEVICE_RESET          BIT(1)
+#define UFS_MTK_SIP_REF_CLK_NOTIFICATION  BIT(3)
 
 /*
  * VS_DEBUGCLOCKENABLE
@@ -57,6 +74,7 @@ enum {
 struct ufs_mtk_host {
 	struct ufs_hba *hba;
 	struct phy *mphy;
+	bool ref_clk_enabled;
 };
 
 #endif /* !_UFS_MEDIATEK_H */