serial driver PMC MSP71xx

Serial driver patch for the PMC-Sierra MSP71xx devices.

There are three different fixes:

1 Fix for DesignWare APB THRE errata: In brief, this is a non-standard
  16550 in that the THRE interrupt will not re-assert itself simply by
  disabling and re-enabling the THRI bit in the IER, it is only re-enabled
  if a character is actually sent out.

  It appears that the "8250-uart-backup-timer.patch" in the "mm" tree
  also fixes it so we have dropped our initial workaround.  This patch now
  needs to be applied on top of that "mm" patch.

2 Fix for Busy Detect on LCR write: The DesignWare APB UART has a feature
  which causes a new Busy Detect interrupt to be generated if it's busy
  when the LCR is written.  This fix saves the value of the LCR and
  rewrites it after clearing the interrupt.

3 Workaround for interrupt/data concurrency issue: The SoC needs to
  ensure that writes that can cause interrupts to be cleared reach the UART
  before returning from the ISR.  This fix reads a non-destructive register
  on the UART so the read transaction completion ensures the previously
  queued write transaction has also completed.

Signed-off-by: Marc St-Jean <Marc_St-Jean@pmc-sierra.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 33 insertions, 0 deletions

diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 90621c3312b..194362d9f5a 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -308,6 +308,7 @@ static unsigned int serial_in(struct uart_8250_port *up, int offset)
 		return inb(up->port.iobase + 1);
 
 	case UPIO_MEM:
+	case UPIO_DWAPB:
 		return readb(up->port.membase + offset);
 
 	case UPIO_MEM32:
@@ -333,6 +334,8 @@ static unsigned int serial_in(struct uart_8250_port *up, int offset)
 static void
 serial_out(struct uart_8250_port *up, int offset, int value)
 {
+	/* Save the offset before it's remapped */
+	int save_offset = offset;
 	offset = map_8250_out_reg(up, offset) << up->port.regshift;
 
 	switch (up->port.iotype) {
@@ -359,6 +362,18 @@ serial_out(struct uart_8250_port *up, int offset, int value)
 			writeb(value, up->port.membase + offset);
 		break;
 
+	case UPIO_DWAPB:
+		/* Save the LCR value so it can be re-written when a
+		 * Busy Detect interrupt occurs. */
+		if (save_offset == UART_LCR)
+			up->lcr = value;
+		writeb(value, up->port.membase + offset);
+		/* Read the IER to ensure any interrupt is cleared before
+		 * returning from ISR. */
+		if (save_offset == UART_TX || save_offset == UART_IER)
+			value = serial_in(up, UART_IER);
+		break;
+
 	default:
 		outb(value, up->port.iobase + offset);
 	}
@@ -373,6 +388,7 @@ serial_out_sync(struct uart_8250_port *up, int offset, int value)
 #ifdef CONFIG_SERIAL_8250_AU1X00
 	case UPIO_AU:
 #endif
+	case UPIO_DWAPB:
 		serial_out(up, offset, value);
 		serial_in(up, UART_LCR);	/* safe, no side-effects */
 		break;
@@ -1389,6 +1405,19 @@ static irqreturn_t serial8250_interrupt(int irq, void *dev_id)
 			handled = 1;
 
 			end = NULL;
+		} else if (up->port.iotype == UPIO_DWAPB &&
+			  (iir & UART_IIR_BUSY) == UART_IIR_BUSY) {
+			/* The DesignWare APB UART has an Busy Detect (0x07)
+			 * interrupt meaning an LCR write attempt occured while the
+			 * UART was busy. The interrupt must be cleared by reading
+			 * the UART status register (USR) and the LCR re-written. */
+			unsigned int status;
+			status = *(volatile u32 *)up->port.private_data;
+			serial_out(up, UART_LCR, up->lcr);
+
+			handled = 1;
+
+			end = NULL;
 		} else if (end == NULL)
 			end = l;
 
@@ -2090,6 +2119,7 @@ static int serial8250_request_std_resource(struct uart_8250_port *up)
 	case UPIO_TSI:
 	case UPIO_MEM32:
 	case UPIO_MEM:
+	case UPIO_DWAPB:
 		if (!up->port.mapbase)
 			break;
 
@@ -2127,6 +2157,7 @@ static void serial8250_release_std_resource(struct uart_8250_port *up)
 	case UPIO_TSI:
 	case UPIO_MEM32:
 	case UPIO_MEM:
+	case UPIO_DWAPB:
 		if (!up->port.mapbase)
 			break;
 
diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
index 0422c0f1f85..a677133ab2d 100644
--- a/drivers/serial/serial_core.c
+++ b/drivers/serial/serial_core.c
@@ -2064,6 +2064,7 @@ uart_report_port(struct uart_driver *drv, struct uart_port *port)
 	case UPIO_MEM32:
 	case UPIO_AU:
 	case UPIO_TSI:
+	case UPIO_DWAPB:
 		snprintf(address, sizeof(address),
 			 "MMIO 0x%lx", port->mapbase);
 		break;
@@ -2409,6 +2410,7 @@ int uart_match_port(struct uart_port *port1, struct uart_port *port2)
 	case UPIO_MEM32:
 	case UPIO_AU:
 	case UPIO_TSI:
+	case UPIO_DWAPB:
 		return (port1->mapbase == port2->mapbase);
 	}
 	return 0;