tcpm: anx74xx: Only connect aux to sbu when DP mode is selected

The anx74xx tcpm driver for the usb_mux_set() function is always
connecting the DP aux lines to the SBU signals regardless of whether
the bit flag MUX_DP_ENABLED was set or not. For CCD opertation the sbu
lines are used to establish a USB connection to H1. This means that if
a PD port ever attaches to a sink debug accessory, usb_mux_set would
result in interrupting the USB connection being used for CCD.

In addition, the anx74xx_tcpm_mux_exit() function had a bug where the
value read from ANALOG_CTRL_5 was being masked by 0x09 and then
written to ANALOG_CTRL_2.

Added functions anx74xx_tcpm_mux_enter_safe_mode() and
anx74xx_tcpm_mux_exit_safe_mode() so that writes to the 3 CTRL
registers that are used to configure ALT_DP mode can be easily
bookended.

BUG=b:36007652
BRANCH=reef
TEST=Connected servo_v4 to port 0 of electro, verified that H1 console
access worked. Then initiated a data role swap so that port 0 on
electro was in DFP mode and the H1 console stayed connected.

- Tested with dingdong that could connect to a 4k monitor.
- Tested with USB3 flash drive.
- Tested Anker USBC -> USBA hub

Change-Id: I2d045134fbdd21b6b492bbeabc85ab23aef73b9a
Signed-off-by: Scott <scollyer@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/451837
Commit-Ready: Scott Collyer <scollyer@chromium.org>
Tested-by: Scott Collyer <scollyer@chromium.org>
Reviewed-by: S Wang <swang@analogix.corp-partner.google.com>
Reviewed-by: Daisuke Nojiri <dnojiri@chromium.org>
(cherry picked from commit d3cc4835bba84f8767480272cd3057c066922ae2)
Reviewed-on: https://chromium-review.googlesource.com/456477
Commit-Queue: Daisuke Nojiri <dnojiri@chromium.org>
Tested-by: Daisuke Nojiri <dnojiri@chromium.org>

1 files changed, 105 insertions, 38 deletions

diff --git a/driver/tcpm/anx74xx.c b/driver/tcpm/anx74xx.c
index ad2c9514d0..c31ec4aa49 100644
--- a/driver/tcpm/anx74xx.c
+++ b/driver/tcpm/anx74xx.c
@@ -41,8 +41,6 @@ struct anx_state {
 
 static struct anx_state anx[CONFIG_USB_PD_PORT_COUNT];
 
-static int anx74xx_set_mux(int port, int polarity);
-
 /* Save the selected rp value */
 static int selected_rp[CONFIG_USB_PD_PORT_COUNT];
 
@@ -151,56 +149,108 @@ static int anx74xx_tcpm_mux_init(int i2c_addr)
 	return EC_SUCCESS;
 }
 
+static int anx74xx_tcpm_mux_enter_safe_mode(int port)
+{
+	int reg;
+
+	if (tcpc_read(port, ANX74XX_REG_ANALOG_CTRL_2, &reg))
+		return EC_ERROR_UNKNOWN;
+	if (tcpc_write(port, ANX74XX_REG_ANALOG_CTRL_2, reg |
+		       ANX74XX_REG_MODE_TRANS))
+		return EC_ERROR_UNKNOWN;
+
+
+	return EC_SUCCESS;
+}
+
+static int anx74xx_tcpm_mux_exit_safe_mode(int port)
+{
+	int reg;
+
+	if (tcpc_read(port, ANX74XX_REG_ANALOG_CTRL_2, &reg))
+		return EC_ERROR_UNKNOWN;
+	if (tcpc_write(port, ANX74XX_REG_ANALOG_CTRL_2, reg &
+		       ~ANX74XX_REG_MODE_TRANS))
+		return EC_ERROR_UNKNOWN;
+
+
+	return EC_SUCCESS;
+}
+
 static int anx74xx_tcpm_mux_exit(int port)
 {
-	int rv = EC_SUCCESS;
-	int reg = 0x0;
+	int reg;
 
-	rv = tcpc_read(port, ANX74XX_REG_ANALOG_CTRL_2, &reg);
-	if (rv)
+	/*
+	 * Safe mode must be entered before any changes are made to the mux
+	 * settings used to enable ALT_DP mode. This funciton is called either
+	 * from anx74xx_tcpm_mux_set when TYPEC_MUX_NONE is selected as the new
+	 * mux state, or when both cc lines are determined to be
+	 * TYPEC_CC_VOLT_OPEN. Therefore, safe mode must be entered and exited
+	 * here so that both entry paths are handled.
+	 */
+	if (anx74xx_tcpm_mux_enter_safe_mode(port))
 		return EC_ERROR_UNKNOWN;
-	rv |= tcpc_write(port, ANX74XX_REG_ANALOG_CTRL_2, reg | ANX74XX_REG_MODE_TRANS);
 
-	/* Clear Bit[7:0] R_SWITCH */
-	rv |= tcpc_write(port, ANX74XX_REG_ANALOG_CTRL_1, 0x0);
+	/* Disconnect aux from sbu */
+	if (tcpc_read(port, ANX74XX_REG_ANALOG_CTRL_2, &reg))
+		return EC_ERROR_UNKNOWN;
+	if (tcpc_write(port, ANX74XX_REG_ANALOG_CTRL_2, reg & 0xf))
+		return EC_ERROR_UNKNOWN;
 
+	/* Clear Bit[7:0] R_SWITCH */
+	if (tcpc_write(port, ANX74XX_REG_ANALOG_CTRL_1, 0x0))
+		return EC_ERROR_UNKNOWN;
 	/* Clear Bit[7:4] R_SWITCH_H */
-	rv |= tcpc_read(port, ANX74XX_REG_ANALOG_CTRL_5, &reg);
-	if (rv)
+	if (tcpc_read(port, ANX74XX_REG_ANALOG_CTRL_5, &reg))
 		return EC_ERROR_UNKNOWN;
-	rv |= tcpc_write(port, ANX74XX_REG_ANALOG_CTRL_5, (reg & 0x0f));
-
-	rv |= tcpc_write(port, ANX74XX_REG_ANALOG_CTRL_2, reg & 0x09);
-	if (rv)
+	if (tcpc_write(port, ANX74XX_REG_ANALOG_CTRL_5, reg & 0x0f))
 		return EC_ERROR_UNKNOWN;
 
-	return rv;
+	/* Exit safe mode */
+	if (anx74xx_tcpm_mux_exit_safe_mode(port))
+		return EC_ERROR_UNKNOWN;
 
+	return EC_SUCCESS;
 }
 
 
-static int anx74xx_set_mux(int port, int polarity)
+static int anx74xx_mux_aux_to_sbu(int port, int polarity, int enabled)
 {
-	int reg, rv = EC_SUCCESS;
+	int reg;
+	const int aux_mask = ANX74XX_REG_AUX_SWAP_SET_CC2 |
+		ANX74XX_REG_AUX_SWAP_SET_CC1;
 
-	rv = tcpc_read(port, ANX74XX_REG_ANALOG_CTRL_2, &reg);
-	if (rv)
+	/*
+	 * Get the current value of analog_ctrl_2 register. Note, that safe mode
+	 * is enabled and exited by the calling function, so only have to worry
+	 * about setting the correct value for the upper 4 bits of analog_ctrl_2
+	 * here.
+	 */
+	if (tcpc_read(port, ANX74XX_REG_ANALOG_CTRL_2, &reg))
 		return EC_ERROR_UNKNOWN;
-	if (polarity) {
-		reg |= ANX74XX_REG_AUX_SWAP_SET_CC2;
-		reg &= ~ANX74XX_REG_AUX_SWAP_SET_CC1;
-	} else {
-		reg |= ANX74XX_REG_AUX_SWAP_SET_CC1;
-		reg &= ~ANX74XX_REG_AUX_SWAP_SET_CC2;
+
+	/* Assume aux_p/n lines are not connected */
+	reg &= ~aux_mask;
+
+	if (enabled) {
+		/* If enabled, connect aux to sbu based on desired  polarity */
+		if (polarity)
+			reg |= ANX74XX_REG_AUX_SWAP_SET_CC2;
+		else
+			reg |= ANX74XX_REG_AUX_SWAP_SET_CC1;
 	}
-	rv = tcpc_write(port, ANX74XX_REG_ANALOG_CTRL_2, reg);
+	/* Write new aux <-> sbu settings */
+	if (tcpc_write(port, ANX74XX_REG_ANALOG_CTRL_2, reg))
+		return EC_ERROR_UNKNOWN;
 
-	return rv;
+	return EC_SUCCESS;
 }
 
 static int anx74xx_tcpm_mux_set(int i2c_addr, mux_state_t mux_state)
 {
-	int reg = 0, val = 0;
+	int reg;
+	int pin_cfg = 0;
 	int rv;
 	int port = i2c_addr;
 
@@ -217,37 +267,54 @@ static int anx74xx_tcpm_mux_set(int i2c_addr, mux_state_t mux_state)
 	if (mux_state & MUX_USB_ENABLED) {
 		/* Set pin assignment D */
 		if (mux_state & MUX_POLARITY_INVERTED) {
-			val = ANX74XX_REG_MUX_DP_MODE_BDF_CC2;
+			pin_cfg = ANX74XX_REG_MUX_DP_MODE_BDF_CC2;
 			reg |= ANX74XX_REG_MUX_SSTX_B;
 		} else {
-			val = ANX74XX_REG_MUX_DP_MODE_BDF_CC1;
+			pin_cfg = ANX74XX_REG_MUX_DP_MODE_BDF_CC1;
 			reg |= ANX74XX_REG_MUX_SSTX_A;
 		}
 	} else if (mux_state & MUX_DP_ENABLED) {
 		/* Set pin assignment C */
 		if (mux_state & MUX_POLARITY_INVERTED) {
-			val = ANX74XX_REG_MUX_DP_MODE_ACE_CC2;
+			pin_cfg = ANX74XX_REG_MUX_DP_MODE_ACE_CC2;
 			reg |= ANX74XX_REG_MUX_ML2_B;
 		} else {
-			val = ANX74XX_REG_MUX_DP_MODE_ACE_CC1;
+			pin_cfg = ANX74XX_REG_MUX_DP_MODE_ACE_CC1;
 			reg |= ANX74XX_REG_MUX_ML2_A;
 		}
-		/* FIXME: disabling DP mode should disable SBU muxes */
-		rv |= anx74xx_set_mux(port, mux_state & MUX_POLARITY_INVERTED);
 	} else if (!mux_state) {
 		return anx74xx_tcpm_mux_exit(port);
 	} else {
 		return  EC_ERROR_UNIMPLEMENTED;
 	}
 
-	rv |= tcpc_write(port, ANX74XX_REG_ANALOG_CTRL_1, val);
+	/*
+	 * Safe mode must be entererd prior to any changes to the mux related to
+	 * ALT_DP mode. Therefore, first enable safe mode prior to updating the
+	 * values for analog_ctrl_1, analog_ctrl_5, and analog_ctrl_2.
+	 */
+	if (anx74xx_tcpm_mux_enter_safe_mode(port))
+		return EC_ERROR_UNKNOWN;
+
+	/* Write updated pin assignment */
+	rv = tcpc_write(port, ANX74XX_REG_ANALOG_CTRL_1, pin_cfg);
+	/* Write Rswitch config bits */
 	rv |= tcpc_write(port, ANX74XX_REG_ANALOG_CTRL_5, reg);
+	if (rv)
+		return EC_ERROR_UNKNOWN;
 
-	anx74xx_set_mux(port, mux_state & MUX_POLARITY_INVERTED ? 1 : 0);
+	/* Configure DP aux to sbu settings */
+	if (anx74xx_mux_aux_to_sbu(port, mux_state & MUX_POLARITY_INVERTED,
+				   mux_state & MUX_DP_ENABLED))
+		return EC_ERROR_UNKNOWN;
+
+	/* Exit safe mode */
+	if (anx74xx_tcpm_mux_exit_safe_mode(port))
+		return EC_ERROR_UNKNOWN;
 
 	anx[port].mux_state = mux_state;
 
-	return rv;
+	return EC_SUCCESS;
 }
 
 /* current mux state  */