linux-kernel - [PATCH v4 05/10] scsi: ufs: ufs-qcom: Allow the first init start with the maximum supported gear

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Message-Id: <1700728577-14729-6-git-send-email-quic_cang@quicinc.com>
Date:   Thu, 23 Nov 2023 00:36:11 -0800
From:   Can Guo <quic_cang@...cinc.com>
To:     quic_cang@...cinc.com, bvanassche@....org, mani@...nel.org,
        adrian.hunter@...el.com, beanhuo@...ron.com, avri.altman@....com,
        junwoo80.lee@...sung.com, martin.petersen@...cle.com
Cc:     linux-scsi@...r.kernel.org, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        linux-arm-msm@...r.kernel.org (open list:UNIVERSAL FLASH STORAGE HOST
        CONTROLLER DRIVER...), linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v4 05/10] scsi: ufs: ufs-qcom: Allow the first init start with the maximum supported gear

During host driver init, the phy_gear is set to the minimum supported gear
(HS_G2). Then, during the first power mode change, the negotiated gear, say
HS-G4, is updated to the phy_gear variable so that in the second init the
updated phy_gear can be used to program the PHY.

But the current code only allows update the phy_gear to a higher value. If
one wants to start the first init with the maximum support gear, say HS-G4,
the phy_gear is not updated to HS-G3 if the device only supports HS-G3.

The original check added there is intend to make sure the phy_gear won't be
updated when gear is scaled down (during clock scaling). Update the check
so that one can start the first init with the maximum support gear without
breaking the original fix by checking the ufshcd_state, that is, allow
update to phy_gear only if power mode change is invoked from
ufshcd_probe_hba().

This change is a preparation patch for the next patches in the same series.

Signed-off-by: Can Guo <quic_cang@...cinc.com>
---
 drivers/ufs/host/ufs-qcom.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
index d4edf58..9613ad9 100644
--- a/drivers/ufs/host/ufs-qcom.c
+++ b/drivers/ufs/host/ufs-qcom.c
@@ -916,16 +916,19 @@ static int ufs_qcom_pwr_change_notify(struct ufs_hba *hba,
 		}
 
 		/*
-		 * Update phy_gear only when the gears are scaled to a higher value. This is
-		 * because, the PHY gear settings are backwards compatible and we only need to
-		 * change the PHY gear settings while scaling to higher gears.
+		 * During UFS driver probe, always update the PHY gear to match the negotiated
+		 * gear, so that, if quirk UFSHCD_QUIRK_REINIT_AFTER_MAX_GEAR_SWITCH is enabled,
+		 * the second init can program the optimal PHY settings. This allows one to start
+		 * the first init with either the minimum or the maximum support gear.
 		 */
-		if (dev_req_params->gear_tx > host->phy_gear) {
+		if (hba->ufshcd_state == UFSHCD_STATE_RESET) {
 			u32 old_phy_gear = host->phy_gear;
 
 			host->phy_gear = dev_req_params->gear_tx;
-			dev_req_params->gear_tx = old_phy_gear;
-			dev_req_params->gear_rx = old_phy_gear;
+			if (dev_req_params->gear_tx > old_phy_gear) {
+				dev_req_params->gear_tx = old_phy_gear;
+				dev_req_params->gear_rx = old_phy_gear;
+			}
 		}
 
 		/* enable the device ref clock before changing to HS mode */
-- 
2.7.4