usb_mux: tusb1064: Add method to set DP Rx EQ gain

This CL adds a method to set DP Rx EQ gain. The previous version of
the driver was enabling a 10 dB gain by default in the init
function. This CL removes setting both gain and EQ_OVERRIDE by
default.

A separate CL in the stack moves the 10dB gain setting to the board.c
file for the only other board that currently is using the TUSB1064.

BUG=b:206059703
BRANCH=quiche
TEST=Verified on gingerbread that both EQ_OVERRIDE is set and the
gain is set in both registers as expected.

Signed-off-by: Scott Collyer <scollyer@google.com>
Change-Id: Id2dc6127d27304d8149f7c51a8d527e046595baf
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3291129
Tested-by: Scott Collyer <scollyer@chromium.org>
Reviewed-by: Diana Z <dzigterman@chromium.org>
Commit-Queue: Scott Collyer <scollyer@chromium.org>

2 files changed, 53 insertions, 21 deletions

diff --git a/driver/usb_mux/tusb1064.c b/driver/usb_mux/tusb1064.c
index c236e3d1ab..6a82aca68f 100644
--- a/driver/usb_mux/tusb1064.c
+++ b/driver/usb_mux/tusb1064.c
@@ -14,12 +14,6 @@
 #error "Must choose CONFIG_USB_MUX_TUSB1044 or CONFIG_USB_MUX_TUSB1064"
 #endif
 
-/*
- * configuration bits which never change in the General Register
- * e.g. REG_GENERAL_DP_EN_CTRL or REG_GENERAL_EQ_OVERRIDE
- */
-#define REG_GENERAL_STATIC_BITS REG_GENERAL_EQ_OVERRIDE
-
 static int tusb1064_read(const struct usb_mux *me, uint8_t reg, uint8_t *val)
 {
 	int buffer = 0xee;
@@ -60,11 +54,54 @@ void tusb1044_hpd_update(const struct usb_mux *me, mux_state_t mux_state)
 }
 #endif
 
+int tusb1064_set_dp_rx_eq(const struct usb_mux *me, int db)
+{
+	uint8_t reg;
+	int rv;
+
+	if (db < TUSB1064_DP_EQ_RX_NEG_0_3_DB || db > TUSB1064_DP_EQ_RX_12_1_DB)
+		return EC_ERROR_INVAL;
+
+	/* Set the requested gain values */
+	reg = TUSB1064_DP1EQ(db) | TUSB1064_DP3EQ(db);
+	rv = tusb1064_write(me, TUSB1064_REG_DP1DP3EQ_SEL, reg);
+	if (rv)
+		return rv;
+
+	reg = TUSB1064_DP0EQ(db) | TUSB1064_DP2EQ(db);
+	rv = tusb1064_write(me, TUSB1064_REG_DP0DP2EQ_SEL, reg);
+	if (rv)
+		return rv;
+
+	/* Enable EQ_OVERRIDE so the gain registers are used */
+	rv = tusb1064_read(me, TUSB1064_REG_GENERAL, &reg);
+	if (rv)
+		return rv;
+
+	reg |= REG_GENERAL_EQ_OVERRIDE;
+
+	return tusb1064_write(me, TUSB1064_REG_GENERAL, reg);
+}
+
 /* Writes control register to set switch mode */
 static int tusb1064_set_mux(const struct usb_mux *me, mux_state_t mux_state,
 			    bool *ack_required)
 {
-	int reg = REG_GENERAL_STATIC_BITS;
+	uint8_t reg;
+	int rv;
+	int mask;
+
+	rv = tusb1064_read(me, TUSB1064_REG_GENERAL, &reg);
+	if (rv)
+		return rv;
+
+	/* Mask bits that may be set in this function */
+	mask = REG_GENERAL_CTLSEL_USB3 | REG_GENERAL_CTLSEL_ANYDP |
+		REG_GENERAL_FLIPSEL;
+#ifdef CONFIG_USB_MUX_TUSB1044
+	mask |= REG_GENERAL_HPDIN_OVERRIDE;
+#endif
+	reg &= ~mask;
 
 	/* This driver does not use host command ACKs */
 	*ack_required = false;
@@ -112,22 +149,8 @@ static int tusb1064_get_mux(const struct usb_mux *me, mux_state_t *mux_state)
 static int tusb1064_init(const struct usb_mux *me)
 {
 	int res;
-	uint8_t reg;
 	bool unused;
 
-	/* Default to "Floating Pin" DP Equalization */
-	reg = TUSB1064_DP1EQ(TUSB1064_DP_EQ_RX_10_0_DB) |
-		TUSB1064_DP3EQ(TUSB1064_DP_EQ_RX_10_0_DB);
-	res = tusb1064_write(me, TUSB1064_REG_DP1DP3EQ_SEL, reg);
-	if (res)
-		return res;
-
-	reg = TUSB1064_DP0EQ(TUSB1064_DP_EQ_RX_10_0_DB) |
-		TUSB1064_DP2EQ(TUSB1064_DP_EQ_RX_10_0_DB);
-	res = tusb1064_write(me, TUSB1064_REG_DP0DP2EQ_SEL, reg);
-	if (res)
-		return res;
-
 	/*
 	 * Note that bypassing the usb_mux API is okay for internal driver calls
 	 * since the task calling init already holds this port's mux lock.
diff --git a/driver/usb_mux/tusb1064.h b/driver/usb_mux/tusb1064.h
index f6aa8e612e..a71d6defa3 100644
--- a/driver/usb_mux/tusb1064.h
+++ b/driver/usb_mux/tusb1064.h
@@ -140,4 +140,13 @@
 void tusb1044_hpd_update(const struct usb_mux *me, mux_state_t mux_state);
 #endif
 
+/**
+ * Set DP Rx Equalization value
+ *
+ * @param *me pointer to usb_mux descriptor
+ * @param db requested gain setting for DP Rx path
+ * @return EC_SUCCESS if db param is valid and I2C is successful
+ */
+int tusb1064_set_dp_rx_eq(const struct usb_mux *me, int db);
+
 #endif /* __CROS_EC_TUSB1064_H */