[PATCH net-next v15 10/13] dpll: sit9531x: implement output pin state on a DPLL

[Ali Rouhi <arouhi@sitime.com>]

From: Oleg Zadorozhnyi <Oleg.Zadorozhnyi@devoxsoftware.com>

An output's state says whether it carries a signal: CONNECTED while it
drives, DISCONNECTED while muted. Setting it forces the output's pads to
Hi-Z, which leaves the divider alone. Output pins are registered from
this patch on.

A mute forces the slot's three Hi-Z pairs, differential, CMOS OutP and
CMOS OutN, inside the programming state; an un-mute releases the force
and the pads return to the loaded configuration. An output is reported
muted only when both pads are forced off.

Signed-off-by: Oleg Zadorozhnyi <Oleg.Zadorozhnyi@devoxsoftware.com>
Signed-off-by: Ali Rouhi <arouhi@sitime.com>
---
 drivers/dpll/sit9531x/core.c | 247 +++++++++++++++++++++++++++++------
 drivers/dpll/sit9531x/core.h |  10 ++
 drivers/dpll/sit9531x/dpll.c | 139 +++++++++++++++++++-
 3 files changed, 355 insertions(+), 41 deletions(-)

diff --git a/drivers/dpll/sit9531x/core.c b/drivers/dpll/sit9531x/core.c
index c7ab33993c28..458de502bc8f 100644
--- a/drivers/dpll/sit9531x/core.c
+++ b/drivers/dpll/sit9531x/core.c
@@ -459,53 +459,42 @@ static int sit9531x_output_forced_hiz(struct sit9531x_dev *sitdev,
 	return 0;
 }
 
-#define SIT9531X_LOOP_LOCK_TRIES	3
-
-/* Close the loops and lock the debug block without committing */
-static void sit9531x_prg_abort(struct sit9531x_dev *sitdev)
+/* Re-read an output's mute state. Caller must hold sitdev->multiop_lock. */
+int sit9531x_output_state_refresh(struct sit9531x_dev *sitdev, u8 out_idx)
 {
-	int rc = -EIO;
-	u8 attempt;
+	bool muted, part;
+	int rc;
 
-	for (attempt = 0; attempt < SIT9531X_LOOP_LOCK_TRIES; attempt++) {
-		rc = sit9531x_write_u8(sitdev, SIT9531X_REG_PRG_DIR_GEN,
-				       SIT9531X_LOOP_LOCK);
-		if (!rc)
-			break;
-		usleep_range(1000, 2000);
-	}
+	lockdep_assert_held(&sitdev->multiop_lock);
+
+	rc = sit9531x_output_forced_hiz(sitdev, out_idx, &muted, &part);
 	if (rc)
-		dev_err(sitdev->dev,
-			"output loops left unlocked after a failed entry: %d\n",
-			rc);
+		return rc;
+
+	sitdev->out[out_idx].enabled = !muted;
+	sitdev->out[out_idx].part_muted = part;
+	sitdev->out[out_idx].state_stale = false;
 
-	sit9531x_write_u8(sitdev, SIT9531X_REG_OUTSYS_DEBUG,
-			  SIT9531X_DEBUG_LOCK_VAL);
+	return 0;
 }
 
-/*
- * Unlock the Page 3 debug registers and enter PRG_CMD; output-system writes
- * take effect only in this state.
- */
-static int sit9531x_prg_enter(struct sit9531x_dev *sitdev)
+static int sit9531x_hiz_set_bit(struct sit9531x_dev *sitdev,
+				unsigned int reg, u8 bit, bool set)
 {
+	u8 cur, new_val;
 	int rc;
 
-	rc = sit9531x_write_u8(sitdev, SIT9531X_REG_OUTSYS_DEBUG,
-			       SIT9531X_DEBUG_UNLOCK_VAL);
+	rc = sit9531x_read_u8(sitdev, reg, &cur);
 	if (rc)
 		return rc;
 
-	rc = sit9531x_write_u8(sitdev, SIT9531X_REG_PRG_DIR_GEN,
-			       SIT9531X_PRG_CMD_STATE);
-	if (rc) {
-		sit9531x_prg_abort(sitdev);
-		return rc;
-	}
+	new_val = set ? (cur | BIT(bit)) : (cur & ~BIT(bit));
 
-	return 0;
+	return sit9531x_write_u8(sitdev, reg, new_val);
 }
 
+#define SIT9531X_LOOP_LOCK_TRIES	3
+
 /*
  * Update the NVM shadow and re-lock the loops after sit9531x_prg_enter(). The
  * sleep is the settling time after loop lock.
@@ -554,6 +543,174 @@ static int sit9531x_prg_commit(struct sit9531x_dev *sitdev)
 	return 0;
 }
 
+/*
+ * Unlock the Page 3 debug registers and enter PRG_CMD; output-system writes
+ * take effect only in this state.
+ */
+static int sit9531x_prg_enter(struct sit9531x_dev *sitdev)
+{
+	int rc;
+
+	rc = sit9531x_write_u8(sitdev, SIT9531X_REG_OUTSYS_DEBUG,
+			       SIT9531X_DEBUG_UNLOCK_VAL);
+	if (rc) {
+		sit9531x_write_close(sitdev, SIT9531X_REG_OUTSYS_DEBUG,
+				     SIT9531X_DEBUG_LOCK_VAL);
+		return rc;
+	}
+
+	rc = sit9531x_write_u8(sitdev, SIT9531X_REG_PRG_DIR_GEN,
+			       SIT9531X_PRG_CMD_STATE);
+	if (rc) {
+		sit9531x_prg_commit(sitdev);
+		return rc;
+	}
+
+	return 0;
+}
+
+/*
+ * Mute or unmute every Hi-Z pair of a slot. Caller must already be in the
+ * programming state.
+ */
+static int sit9531x_output_hiz_write(struct sit9531x_dev *sitdev, u8 slot,
+				     bool mute)
+{
+	u8 mask[SIT9531X_HIZ_PAIRS], state[SIT9531X_HIZ_PAIRS];
+	struct sit9531x_hiz_pair p[SIT9531X_HIZ_PAIRS];
+	int i, rc, undo_rc;
+
+	sit9531x_output_get_hiz_regs(slot, p);
+
+	if (!mute) {
+		for (i = 0; i < SIT9531X_HIZ_PAIRS; i++) {
+			rc = sit9531x_hiz_set_bit(sitdev, p[i].mask, p[i].bit,
+						  false);
+			if (rc)
+				return rc;
+		}
+		return 0;
+	}
+
+	for (i = 0; i < SIT9531X_HIZ_PAIRS; i++) {
+		rc = sit9531x_read_u8(sitdev, p[i].state, &state[i]);
+		if (rc)
+			return rc;
+		rc = sit9531x_read_u8(sitdev, p[i].mask, &mask[i]);
+		if (rc)
+			return rc;
+	}
+
+	/*
+	 * STATE before MASK: enabling the override first can drive the pad for
+	 * one I2C transfer.
+	 */
+	for (i = 0; i < SIT9531X_HIZ_PAIRS; i++) {
+		rc = sit9531x_hiz_set_bit(sitdev, p[i].state, p[i].bit, false);
+		if (!rc)
+			rc = sit9531x_hiz_set_bit(sitdev, p[i].mask, p[i].bit,
+						  true);
+		if (rc)
+			break;
+	}
+	if (!rc)
+		return 0;
+
+	for (; i >= 0; i--) {
+		u8 bit = BIT(p[i].bit);
+
+		undo_rc = sit9531x_hiz_set_bit(sitdev, p[i].mask, p[i].bit,
+					       mask[i] & bit);
+		if (!undo_rc)
+			undo_rc = sit9531x_hiz_set_bit(sitdev, p[i].state,
+						       p[i].bit,
+						       state[i] & bit);
+		if (undo_rc)
+			dev_err(sitdev->dev,
+				"slot%u: Hi-Z override left part applied (%d)\n",
+				slot, undo_rc);
+	}
+
+	return rc;
+}
+
+/* Caller must hold sitdev->multiop_lock. */
+int sit9531x_output_disable(struct sit9531x_dev *sitdev, u8 index)
+{
+	const struct sit9531x_chip_info *info = sitdev->info;
+	int rc, ret, state_rc;
+	bool muted, part;
+	u8 slot;
+
+	lockdep_assert_held(&sitdev->multiop_lock);
+
+	if (index >= info->num_outputs)
+		return -EINVAL;
+
+	slot = info->clkout_map[index];
+	rc = sit9531x_prg_enter(sitdev);
+	if (rc)
+		return rc;
+
+	rc = sit9531x_output_hiz_write(sitdev, slot, true);
+
+	ret = sit9531x_prg_commit(sitdev);
+	if (ret && !rc)
+		rc = ret;
+
+	/* Read back the Hi-Z state */
+	state_rc = sit9531x_output_forced_hiz(sitdev, index, &muted, &part);
+	if (!state_rc) {
+		sitdev->out[index].enabled = !muted;
+		sitdev->out[index].part_muted = part;
+		sitdev->out[index].state_stale = false;
+	} else {
+		sitdev->out[index].state_stale = true;
+		if (!rc)
+			rc = state_rc;
+	}
+
+	return rc;
+}
+
+/* Caller must hold sitdev->multiop_lock. */
+int sit9531x_output_enable(struct sit9531x_dev *sitdev, u8 index)
+{
+	const struct sit9531x_chip_info *info = sitdev->info;
+	int rc, ret, state_rc;
+	bool muted, part;
+	u8 slot;
+
+	lockdep_assert_held(&sitdev->multiop_lock);
+
+	if (index >= info->num_outputs)
+		return -EINVAL;
+
+	slot = info->clkout_map[index];
+	rc = sit9531x_prg_enter(sitdev);
+	if (rc)
+		return rc;
+
+	rc = sit9531x_output_hiz_write(sitdev, slot, false);
+
+	ret = sit9531x_prg_commit(sitdev);
+	if (ret && !rc)
+		rc = ret;
+
+	state_rc = sit9531x_output_forced_hiz(sitdev, index, &muted, &part);
+	if (!state_rc) {
+		sitdev->out[index].enabled = !muted;
+		sitdev->out[index].part_muted = part;
+		sitdev->out[index].state_stale = false;
+	} else {
+		sitdev->out[index].state_stale = true;
+		if (!rc)
+			rc = state_rc;
+	}
+
+	return rc;
+}
+
 /*
  * Procedure:
  *   1. Force PLL into holdover (PLL page reg 0x6F bit 4)
@@ -2084,6 +2241,7 @@ static int sit9531x_out_state_fetch(struct sit9531x_dev *sitdev, u8 index)
 		return rc;
 
 	sitdev->out[index].part_muted = part;
+	sitdev->out[index].state_stale = false;
 
 	/*
 	 * Each PLL page holds a 12-bit output-enable mask: OUT_MAP_LO bits 0-7
@@ -2854,7 +3012,7 @@ static void sit9531x_dpll_pin_unregister(struct sit9531x_dpll_pin *pin)
 	 * Clear before unregistering: callbacks test it under the DPLL device
 	 * lock, which dpll_pin_unregister() also takes.
 	 */
-	pin->dpll_pin = NULL;
+	WRITE_ONCE(pin->dpll_pin, NULL);
 
 	dpll_pin_unregister(sitdpll->dpll_dev, dpll_pin, ops, pin);
 	dpll_pin_put(dpll_pin, &pin->tracker);
@@ -2890,20 +3048,33 @@ static void sit9531x_dpll_pins_unregister(struct sit9531x_dpll *sitdpll)
 	}
 }
 
-/* Check if the pin class has a state callback, which the DPLL core requires */
+/*
+ * An output is registered when routed to this DPLL, whether or not it is
+ * driving.
+ */
 static bool sit9531x_dpll_pin_is_registrable(struct sit9531x_dpll *sitdpll,
 					     enum dpll_pin_direction dir,
 					     u8 index)
 {
 	struct sit9531x_dev *sitdev = sitdpll->dev;
 
-	if (dir != DPLL_PIN_DIRECTION_INPUT)
+	if (dir == DPLL_PIN_DIRECTION_INPUT) {
+		if (index == SIT9531X_MAX_INPUTS)
+			return true;
+		if (index == SIT9531X_INTSYNC_PIN_ID)
+			return false;
+
+		return sit9531x_input_pin_is_registrable(sitdev, index);
+	}
+
+	if (index == SIT9531X_INTSYNC_OUT_PIN_ID)
 		return false;
 
-	if (index == SIT9531X_MAX_INPUTS)
-		return true;
+	if (index >= sitdev->info->num_outputs)
+		return false;
 
-	return sit9531x_input_pin_is_registrable(sitdev, index);
+	return sitdev->out[index].pll_idx == sitdpll->id &&
+	       sitdev->out[index].routed;
 }
 
 static int sit9531x_dpll_pins_register(struct sit9531x_dpll *sitdpll)
diff --git a/drivers/dpll/sit9531x/core.h b/drivers/dpll/sit9531x/core.h
index 6b50b5b64b75..4f3f74ac8d7c 100644
--- a/drivers/dpll/sit9531x/core.h
+++ b/drivers/dpll/sit9531x/core.h
@@ -101,6 +101,9 @@ struct sit9531x_ref {
  * @freq: output frequency in Hz
  * @enabled: output is driving, not forced into Hi-Z
  * @cmos: single-ended; the CMOS pad Hi-Z pairs apply, not the differential one
+ * @state_stale: cached mute state must be read back before it is reported
+ * @ntf_pending: pin change not yet notified; the poll notifies once the state
+ *   is read
  * @part_muted: single-ended with one pad forced and the other not; reported
  *   as driven. The driver's mute forces both pads.
  * @routed: mapped to @pll_idx by the initial configuration; an unrouted
@@ -113,6 +116,8 @@ struct sit9531x_out {
 	u64		freq;
 	bool		enabled;
 	bool		cmos;
+	bool		state_stale;
+	bool		ntf_pending;
 	bool		part_muted;
 	bool		routed;
 	u8		pll_idx;
@@ -281,6 +286,11 @@ int sit9531x_input_prio_remove(struct sit9531x_dev *sitdev, u8 pll_idx,
 int sit9531x_input_prio_add(struct sit9531x_dev *sitdev, u8 pll_idx,
 			    u8 input_idx);
 
+int sit9531x_output_disable(struct sit9531x_dev *sitdev, u8 index);
+int sit9531x_output_enable(struct sit9531x_dev *sitdev, u8 index);
+int sit9531x_output_state_refresh(struct sit9531x_dev *sitdev,
+				  u8 out_idx);
+
 int sit9531x_output_freq_set(struct sit9531x_dev *sitdev, u8 out_idx,
 			     u8 pll_idx, u64 frequency);
 int sit9531x_output_freq_get(struct sit9531x_dev *sitdev, u8 out_idx,
diff --git a/drivers/dpll/sit9531x/dpll.c b/drivers/dpll/sit9531x/dpll.c
index a450a81d02f4..a32d37a396b1 100644
--- a/drivers/dpll/sit9531x/dpll.c
+++ b/drivers/dpll/sit9531x/dpll.c
@@ -184,8 +184,9 @@ const struct dpll_device_ops sit9531x_dpll_device_ops = {
  * NO_SIGNAL on loss of signal; QUAL_FAILED on frequency drift; STANDBY
  * otherwise. The routed reference is used because on loss of signal the device
  * falls back to another listed source and leaves the selection naming the lost
- * one. On manual input select, the routed input is CONNECTED. The XO pin is
- * always CONNECTED.
+ * one. On manual input select, the routed input is CONNECTED. An output is
+ * CONNECTED while driven and DISCONNECTED while muted; SELECTABLE is refused.
+ * The XO pin is always CONNECTED.
  */
 
 /* Caller must hold sitdev->multiop_lock. */
@@ -638,10 +639,114 @@ sit9531x_dpll_output_pin_frequency_set(const struct dpll_pin *pin,
 	return rc;
 }
 
+/*
+ * DISCONNECTED while the output is forced to Hi-Z, by a mute request or by the
+ * loaded profile.
+ */
+static int
+sit9531x_dpll_output_pin_state_on_dpll_get(const struct dpll_pin *pin,
+					   void *pin_priv,
+					   const struct dpll_device *dpll,
+					   void *dpll_priv,
+					   enum dpll_pin_state *state,
+					   struct netlink_ext_ack *extack)
+{
+	struct sit9531x_dpll_pin *dpin = pin_priv;
+	struct sit9531x_dpll *sitdpll = dpll_priv;
+	struct sit9531x_dev *sitdev = sitdpll->dev;
+	const struct sit9531x_out *out;
+	int rc = 0;
+
+	mutex_lock(&sitdev->multiop_lock);
+	out = sit9531x_out_state_get(sitdev, dpin->id);
+	if (out->state_stale)
+		rc = sit9531x_output_state_refresh(sitdev, dpin->id);
+	if (!rc)
+		*state = out->enabled ? DPLL_PIN_STATE_CONNECTED
+				      : DPLL_PIN_STATE_DISCONNECTED;
+	mutex_unlock(&sitdev->multiop_lock);
+	if (rc)
+		NL_SET_ERR_MSG(extack,
+			       "Output mute state could not be read back");
+
+	return rc;
+}
+
+/*
+ * Force Hi-Z through the slot's Hi-Z force/state register pairs: differential,
+ * CMOS OutP and CMOS OutN.
+ */
+static int
+sit9531x_dpll_output_pin_state_on_dpll_set(const struct dpll_pin *pin,
+					   void *pin_priv,
+					   const struct dpll_device *dpll,
+					   void *dpll_priv,
+					   enum dpll_pin_state state,
+					   struct netlink_ext_ack *extack)
+{
+	bool enable = state == DPLL_PIN_STATE_CONNECTED;
+	struct sit9531x_dpll_pin *dpin = pin_priv;
+	struct sit9531x_dpll *sitdpll = dpll_priv;
+	struct sit9531x_dev *sitdev = sitdpll->dev;
+	bool was_enabled, changed;
+	int rc;
+
+	/* An output is routed explicitly, not a selection candidate */
+	if (!enable && state != DPLL_PIN_STATE_DISCONNECTED)
+		return -EINVAL;
+
+	mutex_lock(&sitdev->multiop_lock);
+
+	/*
+	 * Skip a request for the current state: the programming sequence
+	 * unlocks the output loops for its 100 ms commit. One CMOS pad forced
+	 * and the other not is neither state.
+	 */
+	if (!sit9531x_output_state_refresh(sitdev, dpin->id) &&
+	    sitdev->out[dpin->id].enabled == enable &&
+	    !sitdev->out[dpin->id].part_muted) {
+		mutex_unlock(&sitdev->multiop_lock);
+		return 0;
+	}
+
+	was_enabled = sitdev->out[dpin->id].enabled;
+
+	if (enable)
+		rc = sit9531x_output_enable(sitdev, dpin->id);
+	else
+		rc = sit9531x_output_disable(sitdev, dpin->id);
+
+	changed = sitdev->out[dpin->id].enabled != was_enabled ||
+		  sitdev->out[dpin->id].state_stale;
+
+	mutex_unlock(&sitdev->multiop_lock);
+
+	if (rc) {
+		struct dpll_pin *dpll_pin;
+
+		NL_SET_ERR_MSG(extack, "Failed to set output pin state");
+		/*
+		 * The core notifies only a request that succeeded. Teardown
+		 * clears dpll_pin without the core's lock, which is held here;
+		 * read it once, as a set handle stays valid until this returns.
+		 */
+		dpll_pin = READ_ONCE(dpin->dpll_pin);
+		if (changed && dpll_pin && __dpll_pin_change_ntf(dpll_pin)) {
+			mutex_lock(&sitdev->multiop_lock);
+			sitdev->out[dpin->id].ntf_pending = true;
+			mutex_unlock(&sitdev->multiop_lock);
+		}
+	}
+
+	return rc;
+}
+
 static const struct dpll_pin_ops sit9531x_dpll_output_pin_ops = {
 	.direction_get		= sit9531x_dpll_output_pin_direction_get,
 	.frequency_get		= sit9531x_dpll_output_pin_frequency_get,
 	.frequency_set		= sit9531x_dpll_output_pin_frequency_set,
+	.state_on_dpll_get	= sit9531x_dpll_output_pin_state_on_dpll_get,
+	.state_on_dpll_set	= sit9531x_dpll_output_pin_state_on_dpll_set,
 };
 
 const struct dpll_pin_ops *
@@ -703,6 +808,31 @@ void sit9531x_dpll_pin_baseline(struct sit9531x_dpll_pin *pin)
 				   &pin->operstate, &pin->prio);
 }
 
+/*
+ * Re-read an output with a pending change notification; return true once the
+ * read succeeds. Caller must hold sitdev->multiop_lock.
+ */
+static bool
+sit9531x_dpll_output_ntf_pending(struct sit9531x_dev *sitdev,
+				 const struct sit9531x_dpll_pin *pin)
+{
+	struct sit9531x_out *out;
+
+	if (sit9531x_dpll_is_input_pin(pin) ||
+	    pin->id >= sitdev->info->num_outputs)
+		return false;
+
+	out = &sitdev->out[pin->id];
+	if (!out->ntf_pending)
+		return false;
+	if (out->state_stale && sit9531x_output_state_refresh(sitdev, pin->id))
+		return false;
+
+	out->ntf_pending = false;
+
+	return true;
+}
+
 /*
  * Send notifications for changed lock status and pin state; called from
  * sit9531x_dev_periodic_work().
@@ -744,8 +874,11 @@ void sit9531x_dpll_changes_check(struct sit9531x_dpll *sitdpll)
 		bool changed;
 		u8 prio;
 
-		if (!sit9531x_dpll_is_selection_pin(pin))
+		if (!sit9531x_dpll_is_selection_pin(pin)) {
+			pin->ntf_pending |=
+				sit9531x_dpll_output_ntf_pending(sitdev, pin);
 			continue;
+		}
 
 		sit9531x_dpll_pin_snapshot(sitdpll, pin, &state, &operstate,
 					   &prio);
-- 
2.39.2 (Apple Git-143)