Don't hold the hardware mutex across getc(). It can wait indefinitely

for a character to be received. Instead let getc() do any necesary
locking.

4 files changed, 45 insertions, 20 deletions

diff --git a/sys/dev/uart/uart_cpu.h b/sys/dev/uart/uart_cpu.h
index 310d6b9..a3f0dcb 100644
--- a/sys/dev/uart/uart_cpu.h
+++ b/sys/dev/uart/uart_cpu.h
@@ -42,7 +42,7 @@ struct uart_ops {
 	void (*term)(struct uart_bas *);
 	void (*putc)(struct uart_bas *, int);
 	int (*poll)(struct uart_bas *);
-	int (*getc)(struct uart_bas *);
+	int (*getc)(struct uart_bas *, struct mtx *);
 };
 
 extern struct uart_ops uart_i8251_ops;
@@ -150,12 +150,8 @@ uart_poll(struct uart_devinfo *di)
 static __inline int
 uart_getc(struct uart_devinfo *di)
 {
-	int res;
 
-	uart_lock(di->hwmtx);
-	res = di->ops.getc(&di->bas);
-	uart_unlock(di->hwmtx);
-	return (res);
+	return (di->ops.getc(&di->bas, di->hwmtx));
 }
 
 #endif /* _DEV_UART_CPU_H_ */
diff --git a/sys/dev/uart/uart_dev_ns8250.c b/sys/dev/uart/uart_dev_ns8250.c
index 378639f..adb4502 100644
--- a/sys/dev/uart/uart_dev_ns8250.c
+++ b/sys/dev/uart/uart_dev_ns8250.c
@@ -217,7 +217,7 @@ static void ns8250_init(struct uart_bas *bas, int, int, int, int);
 static void ns8250_term(struct uart_bas *bas);
 static void ns8250_putc(struct uart_bas *bas, int);
 static int ns8250_poll(struct uart_bas *bas);
-static int ns8250_getc(struct uart_bas *bas);
+static int ns8250_getc(struct uart_bas *bas, struct mtx *);
 
 struct uart_ops uart_ns8250_ops = {
 	.probe = ns8250_probe,
@@ -321,16 +321,26 @@ ns8250_poll(struct uart_bas *bas)
 }
 
 static int
-ns8250_getc(struct uart_bas *bas)
+ns8250_getc(struct uart_bas *bas, struct mtx *hwmtx)
 {
-	int delay;
+	int c, delay;
+
+	uart_lock(hwmtx);
 
 	/* 1/10th the time to transmit 1 character (estimate). */
 	delay = ns8250_delay(bas);
 
-	while ((uart_getreg(bas, REG_LSR) & LSR_RXRDY) == 0)
+	while ((uart_getreg(bas, REG_LSR) & LSR_RXRDY) == 0) {
+		uart_unlock(hwmtx);
 		DELAY(delay);
-	return (uart_getreg(bas, REG_DATA));
+		uart_lock(hwmtx);
+	}
+
+	c = uart_getreg(bas, REG_DATA);
+
+	uart_unlock(hwmtx);
+
+	return (c);
 }
 
 /*
diff --git a/sys/dev/uart/uart_dev_sab82532.c b/sys/dev/uart/uart_dev_sab82532.c
index 927a681..9ef0bd1 100644
--- a/sys/dev/uart/uart_dev_sab82532.c
+++ b/sys/dev/uart/uart_dev_sab82532.c
@@ -174,7 +174,7 @@ static void sab82532_init(struct uart_bas *bas, int, int, int, int);
 static void sab82532_term(struct uart_bas *bas);
 static void sab82532_putc(struct uart_bas *bas, int);
 static int sab82532_poll(struct uart_bas *bas);
-static int sab82532_getc(struct uart_bas *bas);
+static int sab82532_getc(struct uart_bas *bas, struct mtx *);
 
 struct uart_ops uart_sab82532_ops = {
 	.probe = sab82532_probe,
@@ -307,20 +307,25 @@ sab82532_poll(struct uart_bas *bas)
 {
 
 	if (uart_getreg(bas, SAB_STAR) & SAB_STAR_RFNE)
-		return (sab82532_getc(bas));
+		return (sab82532_getc(bas, NULL));
 	return (-1);
 }
 
 static int
-sab82532_getc(struct uart_bas *bas)
+sab82532_getc(struct uart_bas *bas, struct mtx *hwmtx)
 {
 	int c, delay;
 
+	uart_lock(hwmtx);
+
 	/* 1/10th the time to transmit 1 character (estimate). */
 	delay = sab82532_delay(bas);
 
-	while (!(uart_getreg(bas, SAB_STAR) & SAB_STAR_RFNE))
+	while (!(uart_getreg(bas, SAB_STAR) & SAB_STAR_RFNE)) {
+		uart_unlock(hwmtx);
 		DELAY(delay);
+		uart_lock(hwmtx);
+	}
 
 	while (uart_getreg(bas, SAB_STAR) & SAB_STAR_CEC)
 		;
@@ -338,6 +343,9 @@ sab82532_getc(struct uart_bas *bas)
 		;
 	uart_setreg(bas, SAB_CMDR, SAB_CMDR_RMC);
 	uart_barrier(bas);
+
+	uart_unlock(hwmtx);
+
 	return (c);
 }
 
diff --git a/sys/dev/uart/uart_dev_z8530.c b/sys/dev/uart/uart_dev_z8530.c
index 09895eb..4bde071 100644
--- a/sys/dev/uart/uart_dev_z8530.c
+++ b/sys/dev/uart/uart_dev_z8530.c
@@ -178,7 +178,7 @@ static void z8530_init(struct uart_bas *bas, int, int, int, int);
 static void z8530_term(struct uart_bas *bas);
 static void z8530_putc(struct uart_bas *bas, int);
 static int z8530_poll(struct uart_bas *bas);
-static int z8530_getc(struct uart_bas *bas);
+static int z8530_getc(struct uart_bas *bas, struct mtx *);
 
 struct uart_ops uart_z8530_ops = {
 	.probe = z8530_probe,
@@ -229,12 +229,23 @@ z8530_poll(struct uart_bas *bas)
 }
 
 static int
-z8530_getc(struct uart_bas *bas)
+z8530_getc(struct uart_bas *bas, struct mtx *hwmtx)
 {
+	int c;
 
-	while (!(uart_getreg(bas, REG_CTRL) & BES_RXA))
-		;
-	return (uart_getreg(bas, REG_DATA));
+	uart_lock(hwmtx);
+
+	while (!(uart_getreg(bas, REG_CTRL) & BES_RXA)) {
+		uart_unlock(hwmtx);
+		DELAY(10);
+		uart_lock(hwmtx);
+	}
+
+	c = uart_getreg(bas, REG_DATA);
+
+	uart_unlock(hwmtx);
+
+	return (c);
 }
 
 /*