[PATCH 2/4] phy: qcom: qmp-combo: track whether the cached typec_mux mode was committed to hardware

[Michael Scott]

qmp_combo_typec_mux_set() updates qmp->qmpphy_mode (the cached state)
unconditionally, but only reprograms hardware when qmp->init_count is
non-zero. If pmic_glink_altmode (or any other typec_mux consumer)
calls into the PHY before DWC3 has performed phy_init() -- a real
ordering observed during testing of USB-C role-switch enablement on
Snapdragon X (X1E80100) -- the cache transitions away from the
probe default QMPPHY_MODE_USB3DP but the hardware is never touched.

Subsequent calls (for example on partner detach, where TYPEC_STATE_SAFE
also resolves to QMPPHY_MODE_USB3_ONLY in the !DP-SVID branch) then
match the cached mode and the function bails out early with:

  qcom-qmp-combo-phy faXX000.phy: typec_mux_set: same qmpphy mode, bail out

leaving the lane mux in whatever configuration it powered up in. On
the Dell Latitude 7455 this manifests as the SS lanes being left in
the default state when the first altmode notification arrives during
DWC3 probe, with the function bailing out on every subsequent attach.

Track separately whether the cached mode has actually been committed
to hardware. The bail-out optimization is only safe when the cache
truly reflects the hardware:

  - qmp_combo_typec_mux_set(): bail only when the cached mode matches
    and was committed; clear the committed flag whenever the cache is
    updated, set it again after a successful reprogram inside the
    init_count-guarded block.

  - qmp_combo_com_init(): set the committed flag at the end of a
    successful init, since com_init() programs registers from the
    cached qmpphy_mode.

No behavioural change on platforms where typec_mux_set never fires
before phy_init -- committed remains true through normal operation.

Signed-off-by: Michael Scott <mike.scott@xxxxxxxxxxxxxxxx>
---
 drivers/phy/qualcomm/phy-qcom-qmp-combo.c | 25 +++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-combo.c b/drivers/phy/qualcomm/phy-qcom-qmp-combo.c
index 4057583c0cfe..9b6da783ce60 100644
--- a/drivers/phy/qualcomm/phy-qcom-qmp-combo.c
+++ b/drivers/phy/qualcomm/phy-qcom-qmp-combo.c
@@ -2295,6 +2295,7 @@ struct qmp_combo {
 	struct mutex phy_mutex;
 	int init_count;
 	enum qmpphy_mode qmpphy_mode;
+	bool qmpphy_mode_committed;
 
 	struct phy *usb_phy;
 	enum phy_mode phy_mode;
@@ -3747,6 +3748,9 @@ static int qmp_combo_com_init(struct qmp_combo *qmp, bool force)
 	qphy_setbits(qmp->pcs, cfg->regs[QPHY_PCS_POWER_DOWN_CONTROL],
 			SW_PWRDN);
 
+	/* com_init() just programmed registers from qmp->qmpphy_mode. */
+	qmp->qmpphy_mode_committed = true;
+
 	return 0;
 
 err_assert_reset:
@@ -4507,9 +4511,22 @@ static int qmp_combo_typec_mux_set(struct typec_mux_dev *mux, struct typec_mux_s
 		new_mode = QMPPHY_MODE_USB3_ONLY;
 	}
 
+	/*
+	 * Fast-path bail only when the cached mode is also known to be
+	 * committed to hardware. The cache may be ahead of the hardware
+	 * if a typec_mux_set arrived while the PHY had not yet been
+	 * initialised (init_count == 0); in that case the cache update
+	 * below was the only thing that ran, and we still need to drive
+	 * the registers when the PHY does come up.
+	 */
 	if (new_mode == qmp->qmpphy_mode) {
-		dev_dbg(qmp->dev, "typec_mux_set: same qmpphy mode, bail out\n");
-		return 0;
+		if (qmp->qmpphy_mode_committed) {
+			dev_dbg(qmp->dev,
+				"typec_mux_set: same qmpphy mode (committed), bail out\n");
+			return 0;
+		}
+		dev_dbg(qmp->dev,
+			"typec_mux_set: same qmpphy mode but uncommitted; reprogramming\n");
 	}
 
 	if (qmp->qmpphy_mode != QMPPHY_MODE_USB3_ONLY && qmp->dp_powered_on) {
@@ -4521,6 +4538,7 @@ static int qmp_combo_typec_mux_set(struct typec_mux_dev *mux, struct typec_mux_s
 		qmp->qmpphy_mode, new_mode);
 
 	qmp->qmpphy_mode = new_mode;
+	qmp->qmpphy_mode_committed = false;
 
 	if (qmp->init_count) {
 		if (qmp->usb_init_count)
@@ -4549,6 +4567,9 @@ static int qmp_combo_typec_mux_set(struct typec_mux_dev *mux, struct typec_mux_s
 			if (qmp->dp_init_count)
 				cfg->dp_aux_init(qmp);
 		}
+
+		/* Reprogram complete; cache now reflects hardware. */
+		qmp->qmpphy_mode_committed = true;
 	}
 
 	return 0;
-- 
2.53.0