scsi: ufs: core: Introduce a new ufshcd vops negotiate_pwr_mode()

Most vendor specific implemenations of vops pwr_change_notify(PRE_CHANGE)
are fulfilling two things at once:

 - Vendor specific target power mode negotiation

 - Vendor specific power mode change preparation

When TX Equalization is added into consideration, before power mode change
to a target power mode, TX Equalization Training (EQTR) needs be done for
that target power mode. In addition, UFSHCI spec requires to start TX EQTR
from HS-G1 (the most reliable High Speed Gear).

Adding TX EQTR before pwr_change_notify(PRE_CHANGE) is not applicable
because we don't know the negotiated power mode yet.

Adding TX EQTR post pwr_change_notify(PRE_CHANGE) is inappropriate because
pwr_change_notify(PRE_CHANGE) has finished preparation for a power mode
change to negotiated power mode, yet we are changing power mode to HS-G1
for TX EQTR.

Add a new vops negotiate_pwr_mode() so that vendor specific power mode
negotiation can be fulfilled in its vendor specific implementations.  Later
on, TX EQTR can be added post vops negotiate_pwr_mode() and before vops
pwr_change_notify(PRE_CHANGE).

Reviewed-by: Bean Huo <beanhuo@micron.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Can Guo <can.guo@oss.qualcomm.com>
Reviewed-by: Peter Wang <peter.wang@mediatek.com>
Link: https://patch.msgid.link/20260325152154.1604082-2-can.guo@oss.qualcomm.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

2 files changed, 68 insertions, 16 deletions

diff --git a/drivers/ufs/core/ufshcd-priv.h b/drivers/ufs/core/ufshcd-priv.h
index 37c32071e754..f1cec1cd01d2 100644
--- a/drivers/ufs/core/ufshcd-priv.h
+++ b/drivers/ufs/core/ufshcd-priv.h
@@ -167,14 +167,24 @@ static inline int ufshcd_vops_link_startup_notify(struct ufs_hba *hba,
 	return 0;
 }
 
+static inline int ufshcd_vops_negotiate_pwr_mode(struct ufs_hba *hba,
+						 const struct ufs_pa_layer_attr *dev_max_params,
+						 struct ufs_pa_layer_attr *dev_req_params)
+{
+	if (hba->vops && hba->vops->negotiate_pwr_mode)
+		return hba->vops->negotiate_pwr_mode(hba, dev_max_params,
+					dev_req_params);
+
+	return -ENOTSUPP;
+}
+
 static inline int ufshcd_vops_pwr_change_notify(struct ufs_hba *hba,
 				enum ufs_notify_change_status status,
-				const struct ufs_pa_layer_attr *dev_max_params,
 				struct ufs_pa_layer_attr *dev_req_params)
 {
 	if (hba->vops && hba->vops->pwr_change_notify)
 		return hba->vops->pwr_change_notify(hba, status,
-					dev_max_params, dev_req_params);
+					dev_req_params);
 
 	return -ENOTSUPP;
 }
diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 847b55789bb8..33bbdd940b06 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -336,8 +336,6 @@ static void ufshcd_suspend_clkscaling(struct ufs_hba *hba);
 static int ufshcd_scale_clks(struct ufs_hba *hba, unsigned long freq,
 			     bool scale_up);
 static irqreturn_t ufshcd_intr(int irq, void *__hba);
-static int ufshcd_change_power_mode(struct ufs_hba *hba,
-			     struct ufs_pa_layer_attr *pwr_mode);
 static int ufshcd_setup_hba_vreg(struct ufs_hba *hba, bool on);
 static int ufshcd_setup_vreg(struct ufs_hba *hba, bool on);
 static inline int ufshcd_config_vreg_hpm(struct ufs_hba *hba,
@@ -4663,8 +4661,26 @@ static int ufshcd_get_max_pwr_mode(struct ufs_hba *hba)
 	return 0;
 }
 
-static int ufshcd_change_power_mode(struct ufs_hba *hba,
-			     struct ufs_pa_layer_attr *pwr_mode)
+/**
+ * ufshcd_dme_change_power_mode() - UniPro DME Power Mode change sequence
+ * @hba: per-adapter instance
+ * @pwr_mode: pointer to the target power mode (gear/lane) attributes
+ *
+ * This function handles the low-level DME (Device Management Entity)
+ * configuration required to transition the UFS link to a new power mode. It
+ * performs the following steps:
+ * 1. Checks if the requested mode matches the current state.
+ * 2. Sets M-PHY and UniPro attributes including Gear (PA_RXGEAR/TXGEAR),
+ *    Lanes, Termination, and HS Series (PA_HSSERIES).
+ * 3. Configures default UniPro timeout values (DL_FC0, etc.) unless
+ *    explicitly skipped via quirks.
+ * 4. Triggers the actual hardware mode change via ufshcd_uic_change_pwr_mode().
+ * 5. Updates the HBA's cached power information on success.
+ *
+ * Return: 0 on success, non-zero error code on failure.
+ */
+static int ufshcd_dme_change_power_mode(struct ufs_hba *hba,
+					struct ufs_pa_layer_attr *pwr_mode)
 {
 	int ret;
 
@@ -4749,6 +4765,34 @@ static int ufshcd_change_power_mode(struct ufs_hba *hba,
 }
 
 /**
+ * ufshcd_change_power_mode() - Change UFS Link Power Mode
+ * @hba: per-adapter instance
+ * @pwr_mode: pointer to the target power mode (gear/lane) attributes
+ *
+ * This function handles the high-level sequence for changing the UFS link
+ * power mode. It triggers vendor-specific pre-change notification,
+ * executes the DME (Device Management Entity) power mode change sequence,
+ * and, upon success, triggers vendor-specific post-change notification.
+ *
+ * Return: 0 on success, non-zero error code on failure.
+ */
+int ufshcd_change_power_mode(struct ufs_hba *hba,
+			     struct ufs_pa_layer_attr *pwr_mode)
+{
+	int ret;
+
+	ufshcd_vops_pwr_change_notify(hba, PRE_CHANGE, pwr_mode);
+
+	ret = ufshcd_dme_change_power_mode(hba, pwr_mode);
+
+	if (!ret)
+		ufshcd_vops_pwr_change_notify(hba, POST_CHANGE, pwr_mode);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(ufshcd_change_power_mode);
+
+/**
  * ufshcd_config_pwr_mode - configure a new power mode
  * @hba: per-adapter instance
  * @desired_pwr_mode: desired power configuration
@@ -4761,19 +4805,17 @@ int ufshcd_config_pwr_mode(struct ufs_hba *hba,
 	struct ufs_pa_layer_attr final_params = { 0 };
 	int ret;
 
-	ret = ufshcd_vops_pwr_change_notify(hba, PRE_CHANGE,
-					desired_pwr_mode, &final_params);
+	ret = ufshcd_vops_negotiate_pwr_mode(hba, desired_pwr_mode,
+					     &final_params);
+	if (ret) {
+		if (ret != -ENOTSUPP)
+			dev_err(hba->dev, "Failed to negotiate power mode: %d, use desired as is\n",
+				ret);
 
-	if (ret)
 		memcpy(&final_params, desired_pwr_mode, sizeof(final_params));
+	}
 
-	ret = ufshcd_change_power_mode(hba, &final_params);
-
-	if (!ret)
-		ufshcd_vops_pwr_change_notify(hba, POST_CHANGE, NULL,
-					&final_params);
-
-	return ret;
+	return ufshcd_change_power_mode(hba, &final_params);
 }
 EXPORT_SYMBOL_GPL(ufshcd_config_pwr_mode);