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serial/8250_pci: Need to clear FIFOs for KT serial on BI

PATCH In review sudhakar 2 participants 2 messages Apr 3, 2012 TTY layer and serial drivers

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#0 lore raw

PATCH 2/2 serial/8250_pci: Need to clear FIFOs for KT serial on BI

From: Sudhakar Mamillapalli <[email protected]>

When using SOL thru a KT serial device and Intel ME gets reset the serial FIFOs need to be cleared for sane SOL output. On a reset the device assertes BI, so using that as a cue FIFOs are cleared. One other problem is that the serial registers might temporarily go to 0 on reset for this device. So instead of restoring IER register from read value in poll_char and other functions we get the value from uart_8250_port which should have the same value.

Signed-off-by Sudhakar Mamillapalli <[email protected]>
Acked-by Dan Williams <[email protected]>
Acked-by Nhan H Mai <[email protected]>
---
 drivers/tty/serial/8250/8250.c     |   37 +++++++++++++++++++++++++++++++++--
 drivers/tty/serial/8250/8250_pci.c |    3 +-
 include/linux/serial_core.h        |    3 +-
 3 files changed, 38 insertions(+), 5 deletions(-)
drivers/tty/serial/8250/8250.c +34 -3
index 5fb0157..c61799e 100644
@@ -282,6 +282,13 @@ static const struct serial8250_config uart_config[] = {
 		.fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
 		.flags		= UART_CAP_FIFO | UART_CAP_AFE | UART_CAP_EFR,
 	},
+	[PORT_KT_SERIAL] = {
+		.name		= "KTSERIAL",
+		.fifo_size	= 16,
+		.tx_loadsz	= 16,
+		.fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
+		.flags		= UART_CAP_FIFO,
+	},
 };
 
 #if defined(CONFIG_MIPS_ALCHEMY)

@@ -1363,6 +1370,7 @@ serial8250_rx_chars(struct uart_8250_port *up, unsigned char lsr)
 	struct uart_port *port = &up->port;
 	struct tty_struct *tty = port->state->port.tty;
 	unsigned char ch;
+	unsigned char fcr;
 	int max_count = 256;
 	char flag;
 

@@ -1385,6 +1393,16 @@ serial8250_rx_chars(struct uart_8250_port *up, unsigned char lsr)
 		lsr |= up->lsr_saved_flags;
 		up->lsr_saved_flags = 0;
 
+		if ((up->port.type == PORT_KT_SERIAL) && (lsr & UART_LSR_BI)) {
+			/*
+			 * For KT serial device if break interrupt then got
+			 * to clear the fifos for sane SOL output.
+			 */
+			serial8250_clear_fifos(up);
+			fcr = uart_config[up->port.type].fcr;
+			serial_port_out(port, UART_FCR, fcr);
+		}
+
 		if (unlikely(lsr & UART_LSR_BRK_ERROR_BITS)) {
 			/*
 			 * For statistics only

@@ -1729,7 +1747,12 @@ static void serial8250_backup_timeout(unsigned long data)
 	 * based handler.
 	 */
 	if (up->port.irq) {
-		ier = serial_in(up, UART_IER);
+		/*
+		 * Get the ier value from up->ier rather than reading the
+		 * register, since some SOL uarts(for e.g. KT serial) it
+		 * goes to 0 momentarily on BMC reset.
+		 */
+		ier = up->ier;
 		serial_out(up, UART_IER, 0);
 	}
 

@@ -1896,8 +1919,12 @@ static void serial8250_put_poll_char(struct uart_port *port,
 
 	/*
 	 *	First save the IER then disable the interrupts
+	 *
+	 *      Get the ier value from up->ier rather than reading the
+	 *      register, since some SOL uarts(for e.g. KT serial) it
+	 *      goes to 0 momentarily on BMC reset.
 	 */
-	ier = serial_port_in(port, UART_IER);
+	ier = up->ier;
 	if (up->capabilities & UART_CAP_UUE)
 		serial_port_out(port, UART_IER, UART_IER_UUE);
 	else

@@ -2818,8 +2845,12 @@ serial8250_console_write(struct console *co, const char *s, unsigned int count)
 
 	/*
 	 *	First save the IER then disable the interrupts
+	 *
+	 *      Get the ier value from up->ier rather than reading the
+	 *      register, since some SOL uarts(for e.g. KT serial) it
+	 *      goes to 0 momentarily on BMC reset.
 	 */
-	ier = serial_port_in(port, UART_IER);
+	ier = up->ier;
 
 	if (up->capabilities & UART_CAP_UUE)
 		serial_port_out(port, UART_IER, UART_IER_UUE);
drivers/tty/serial/8250/8250_pci.c +2 -1
index 858dca8..1aebe63 100644
@@ -1096,7 +1096,8 @@ static int kt_serial_setup(struct serial_private *priv,
 			   const struct pciserial_board *board,
 			   struct uart_port *port, int idx)
 {
-	port->flags |= UPF_BUG_THRE;
+	port->flags |= UPF_BUG_THRE | UPF_FIXED_TYPE;
+	port->type = PORT_KT_SERIAL;
 	return skip_tx_en_setup(priv, board, port, idx);
 }
include/linux/serial_core.h +2 -1
index 2db407a..efd7d0d 100644
@@ -47,7 +47,8 @@
 #define PORT_U6_16550A	19	/* ST-Ericsson U6xxx internal UART */
 #define PORT_TEGRA	20	/* NVIDIA Tegra internal UART */
 #define PORT_XR17D15X	21	/* Exar XR17D15x UART */
-#define PORT_MAX_8250	21	/* max port ID */
+#define PORT_KT_SERIAL	22	/* KT Serial SOL device */
+#define PORT_MAX_8250	22	/* max port ID */
 
 /*
  * ARM specific type numbers.  These are not currently guaranteed
Signature · 1 line
1.7.8.4
#1 lore raw
Quoted 5 lines · On Tue, 3 Apr 2012 12:47:21 -0700 sudhakar <[email protected]> wrote:

From: Sudhakar Mamillapalli <[email protected]>

When using SOL thru a KT serial device and Intel ME gets reset the serial FIFOs need to be cleared for sane SOL output. On

Acronym failure.

Please remember that people looking at a patch and even more so people in future maintaining the code will not have any idea wtf you are talking about !

Expand the acronyms in a patch and include a bit of context.

Quoted 4 lines
drivers/tty/serial/8250/8250.c +0 -0
@@ -1385,6 +1393,16 @@ serial8250_rx_chars(struct uart_8250_port *up, unsigned char lsr)
 		lsr |= up->lsr_saved_flags;
 		up->lsr_saved_flags = 0;

drivers/tty/serial/8250/8250.c serial8250_rx_chars(struct uart_8250_port *up, unsigned char lsr) · line 1405

Quoted 10 lines
drivers/tty/serial/8250/8250.c +10 -0
+		if ((up->port.type == PORT_KT_SERIAL) && (lsr & UART_LSR_BI)) {
+			/*
+			 * For KT serial device if break interrupt then got
+			 * to clear the fifos for sane SOL output.
+			 */
+			serial8250_clear_fifos(up);
+			fcr = uart_config[up->port.type].fcr;
+			serial_port_out(port, UART_FCR, fcr);
+		}
+

This wants to be some kind of call back handled case not more stuff in the core 8250.c which we are trying to drive all the special cases back out of.

Quoted 5 lines
drivers/tty/serial/8250/8250.c +0 -0
 		if (unlikely(lsr & UART_LSR_BRK_ERROR_BITS)) {
 			/*
 			 * For statistics only

@@ -1729,7 +1747,12 @@ static void serial8250_backup_timeout(unsigned long data)
 	 * based handler.

drivers/tty/serial/8250/8250.c static void serial8250_backup_timeout(unsigned long data) · line 1756

Quoted 10 lines
drivers/tty/serial/8250/8250.c +6 -1
 	 */
 	if (up->port.irq) {
-		ier = serial_in(up, UART_IER);
+		/*
+		 * Get the ier value from up->ier rather than reading the
+		 * register, since some SOL uarts(for e.g. KT serial) it
+		 * goes to 0 momentarily on BMC reset.
+		 */
+		ier = up->ier;
 		serial_out(up, UART_IER, 0);

Surely you do this fixup in your own private serial_in method as various other chips do for all sorts of brain damage.

Quoted 4 lines
drivers/tty/serial/8250/8250.c +0 -0
 	}
 

@@ -1896,8 +1919,12 @@ static void serial8250_put_poll_char(struct uart_port *port,

drivers/tty/serial/8250/8250.c static void serial8250_put_poll_char(struct uart_port *port, · line 1928

Quoted 10 lines
drivers/tty/serial/8250/8250.c +5 -1
 	/*
 	 *	First save the IER then disable the interrupts
+	 *
+	 *      Get the ier value from up->ier rather than reading the
+	 *      register, since some SOL uarts(for e.g. KT serial) it
+	 *      goes to 0 momentarily on BMC reset.
 	 */
-	ier = serial_port_in(port, UART_IER);
+	ier = up->ier;
 	if (up->capabilities & UART_CAP_UUE)

Ditto

Quoted 4 lines
drivers/tty/serial/8250/8250.c +0 -0
 		serial_port_out(port, UART_IER, UART_IER_UUE);
 	else

@@ -2818,8 +2845,12 @@ serial8250_console_write(struct console *co, const char *s, unsigned int count)

drivers/tty/serial/8250/8250.c serial8250_console_write(struct console *co, const char *s, unsigned int count) · line 2854

Quoted 10 lines
drivers/tty/serial/8250/8250.c +5 -1
 	/*
 	 *	First save the IER then disable the interrupts
+	 *
+	 *      Get the ier value from up->ier rather than reading the
+	 *      register, since some SOL uarts(for e.g. KT serial) it
+	 *      goes to 0 momentarily on BMC reset.
 	 */
-	ier = serial_port_in(port, UART_IER);
+	ier = up->ier;

Ditto

In fact as far as I can see this boils down to

- a private serial_in method
- possibly adding a callback for special break handling. You may even be able to hide that in serial_in methods, but its probably better explicit.

Alan