revise the uart tx connect/disconnect functionsstabilize-quickfix-12871.27.B-cr50_stabstabilize-12871.91.B-cr50_stabstabilize-12871.65.B-cr50_stabstabilize-12871.57.B-cr50_stabstabilize-12871.253.B-cr50_stabstabilize-12871.24.B-cr50_stabstabilize-12871.103.B-cr50_stabstabilize-12871.102.B-cr50_stabstabilize-12859.B-cr50_stabrelease-R81-12871.B-cr50_stab

This patch reduces redundant condition checking in connecting
or disconnecting UART TX.

BUG=none
BRANCH=cr50
TEST=manually checked ccd state with/without servo connection and/or
ccd connection.

[AFTER]
> ccdstate
AP:      on
AP UART: on
EC:      on
Rdd:     connected
Servo:   connected
CCD EXT: enabled
State flags: UARTAP UARTEC
CCD ports blocked: (none)

> ccdstate
AP:      on
AP UART: on
EC:      on
Rdd:     disconnected
Servo:   connected
CCD EXT: disabled
State flags:
CCD ports blocked: (none)

> ccdstate
AP:      on
AP UART: on
EC:      on
Rdd:     connected
Servo:   undetectable
CCD EXT: enabled
State flags: UARTAP+TX UARTEC+TX I2C SPI
CCD ports blocked: (none)

> ccdstate
AP:      off
AP UART: off
EC:      on
Rdd:     connected
Servo:   undetectable
CCD EXT: enabled
State flags: UARTEC+TX I2C SPI
CCD ports blocked: (none)

> ccdstate
AP:      on
AP UART: on
EC:      on
Rdd:     connected
Servo:   disconnected
CCD EXT: enabled
State flags: UARTAP+TX I2C SPI
CCD ports blocked: EC

> ccdstate
AP:      on
AP UART: on
EC:      on
Rdd:     connected
Servo:   disconnected
CCD EXT: enabled
State flags: I2C SPI
CCD ports blocked: AP EC

> ccdstate
AP:      on
AP UART: on
EC:      on
Rdd:     connected
Servo:   ignored
CCD EXT: enabled
State flags: UARTAP+TX UARTEC+TX I2C SPI
CCD ports blocked: IGNORE_SERVO
WARNING: enabling UART while servo is connected may damage hardware

Change-Id: Icea2978b15e15bbf7cea8e48fd2bf4fdecc78f46
Signed-off-by: Namyoon Woo <namyoon@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2013823
Reviewed-by: Mary Ruthven <mruthven@chromium.org>

2 files changed, 11 insertions, 45 deletions

diff --git a/board/cr50/rdd.c b/board/cr50/rdd.c
index 2d1403ec02..21d1357df8 100644
--- a/board/cr50/rdd.c
+++ b/board/cr50/rdd.c
@@ -78,60 +78,32 @@ int uart_tx_is_connected(int uart)
 	return !uart_bitbang_is_enabled() && GREAD(PINMUX, DIOB5_SEL);
 }
 
-/**
- * Connect the UART pin to the given signal
- *
- * @param uart		the uart peripheral number
- * @param signal	the pinmux selector value for the gpio or peripheral
- *			function. 0 to disable the output.
- */
-static void uart_select_tx(int uart, int signal)
+static void uartn_tx_connect(int uart)
 {
+	/* Connect the TX pin to UART peripheral */
 	if (uart == UART_AP) {
-		GWRITE(PINMUX, DIOA7_SEL, signal);
+		GWRITE(PINMUX, DIOA7_SEL, GC_PINMUX_UART1_TX_SEL);
 	} else {
-		GWRITE(PINMUX, DIOB5_SEL, signal);
+		GWRITE(PINMUX, DIOB5_SEL, GC_PINMUX_UART2_TX_SEL);
 
 		/* Remove the pulldown when we are driving the signal */
-		GWRITE_FIELD(PINMUX, DIOB5_CTL, PD, signal ? 0 : 1);
+		GWRITE_FIELD(PINMUX, DIOB5_CTL, PD, 0);
 	}
 }
 
-void uartn_tx_connect(int uart)
+static void uartn_tx_disconnect(int uart)
 {
-	/*
-	 * Don't drive TX unless the debug cable is connected (we have
-	 * something to transmit) and servo is disconnected (we won't be
-	 * drive-fighting with servo).
-	 */
-	if (servo_is_connected() || !ccd_ext_is_enabled())
-		return;
-
+	/* Disconnect the TX pin from UART peripheral */
 	if (uart == UART_AP) {
-		if (!ccd_is_cap_enabled(CCD_CAP_GSC_TX_AP_RX))
-			return;
-
-		if (!ap_uart_is_on())
-			return;
-
-		uart_select_tx(UART_AP, GC_PINMUX_UART1_TX_SEL);
+		GWRITE(PINMUX, DIOA7_SEL, 0);
 	} else {
-		if (!ccd_is_cap_enabled(CCD_CAP_GSC_TX_EC_RX))
-			return;
+		GWRITE(PINMUX, DIOB5_SEL, 0);
 
-		if (!ec_is_on())
-			return;
-
-		uart_select_tx(UART_EC, GC_PINMUX_UART2_TX_SEL);
+		/* Set up the pulldown */
+		GWRITE_FIELD(PINMUX, DIOB5_CTL, PD, 1);
 	}
 }
 
-void uartn_tx_disconnect(int uart)
-{
-	/* Disconnect the TX pin from UART peripheral */
-	uart_select_tx(uart, 0);
-}
-
 /*
  * Flags for the current CCD device state.  This is used for determining what
  * hardware devices we've enabled now, and which we want enabled.
diff --git a/chip/g/uartn.h b/chip/g/uartn.h
index bfb7772518..e0d0c140b3 100644
--- a/chip/g/uartn.h
+++ b/chip/g/uartn.h
@@ -82,12 +82,6 @@ void uartn_tx_stop(int uart);
  */
 int uart_tx_is_connected(int uart);
 
-/* Connect TX pin for the UART */
-void uartn_tx_connect(int uart);
-
-/* Disconnect TX pin for the UART */
-void uartn_tx_disconnect(int uart);
-
 /**
  * Return non-zero if TX and RX are enabled for the UART.
  *