8250: add a UPIO_DWAPB32 for 32 bit accesses

Some platforms contain a Synopsys DesignWare APB UART that is attached
to a 32-bit APB bus where sub-word accesses are not allowed. Add a new
IO type (UPIO_DWAPB32) that performs 32 bit acccesses to the UART.

v2:
	- don't test for 32 bit in the output fast path, provide a
	  separate dwabp32_serial_out() function. Refactor
	  dwabp_serial_out() so that we can reuse the LCR saving
	  code.
v3:
	- rebased on top of "8250: use container_of() instead of
	  casting"
Signed-off-by: NJamie Iles <jamie@jamieiles.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/serial/8250.c

@@ -454,22 +454,40 @@ static void tsi_serial_out(struct uart_port *p, int offset, int value)
 		writeb(value, p->membase + offset);
 }
 
-static void dwapb_serial_out(struct uart_port *p, int offset, int value)
+/* Save the LCR value so it can be re-written when a Busy Detect IRQ occurs. */
+static inline void dwapb_save_out_value(struct uart_port *p, int offset,
+					int value)
 {
-	int save_offset = offset;
-	offset = map_8250_out_reg(p, offset) << p->regshift;
-	/* Save the LCR value so it can be re-written when a
-	 * Busy Detect interrupt occurs. */
-	if (save_offset == UART_LCR) {
 	struct uart_8250_port *up =
 		container_of(p, struct uart_8250_port, port);
+
+	if (offset == UART_LCR)
 		up->lcr = value;
-	}
+}
+
+/* Read the IER to ensure any interrupt is cleared before returning from ISR. */
+static inline void dwapb_check_clear_ier(struct uart_port *p, int offset)
+{
+	if (offset == UART_TX || offset == UART_IER)
+		p->serial_in(p, UART_IER);
+}
+
+static void dwapb_serial_out(struct uart_port *p, int offset, int value)
+{
+	int save_offset = offset;
+	offset = map_8250_out_reg(p, offset) << p->regshift;
+	dwapb_save_out_value(p, save_offset, value);
 	writeb(value, p->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 = p->serial_in(p, UART_IER);
+	dwapb_check_clear_ier(p, save_offset);
+}
+
+static void dwapb32_serial_out(struct uart_port *p, int offset, int value)
+{
+	int save_offset = offset;
+	offset = map_8250_out_reg(p, offset) << p->regshift;
+	dwapb_save_out_value(p, save_offset, value);
+	writel(value, p->membase + offset);
+	dwapb_check_clear_ier(p, save_offset);
 }
 
 static unsigned int io_serial_in(struct uart_port *p, int offset)
@@ -520,6 +538,11 @@ static void set_io_from_upio(struct uart_port *p)
 		p->serial_out = dwapb_serial_out;
 		break;
 
+	case UPIO_DWAPB32:
+		p->serial_in = mem32_serial_in;
+		p->serial_out = dwapb32_serial_out;
+		break;
+
 	default:
 		p->serial_in = io_serial_in;
 		p->serial_out = io_serial_out;
@@ -538,6 +561,7 @@ serial_out_sync(struct uart_8250_port *up, int offset, int value)
 	case UPIO_MEM32:
 	case UPIO_AU:
 	case UPIO_DWAPB:
+	case UPIO_DWAPB32:
 		p->serial_out(p, offset, value);
 		p->serial_in(p, UART_LCR);	/* safe, no side-effects */
 		break;
@@ -1587,7 +1611,8 @@ static irqreturn_t serial8250_interrupt(int irq, void *dev_id)
 			handled = 1;
 
 			end = NULL;
-		} else if (up->port.iotype == UPIO_DWAPB &&
+		} else if ((up->port.iotype == UPIO_DWAPB ||
+			    up->port.iotype == UPIO_DWAPB32) &&
 			  (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
@@ -2492,6 +2517,7 @@ static int serial8250_request_std_resource(struct uart_8250_port *up)
 	case UPIO_MEM32:
 	case UPIO_MEM:
 	case UPIO_DWAPB:
+	case UPIO_DWAPB32:
 		if (!up->port.mapbase)
 			break;
 
@@ -2529,6 +2555,7 @@ static void serial8250_release_std_resource(struct uart_8250_port *up)
 	case UPIO_MEM32:
 	case UPIO_MEM:
 	case UPIO_DWAPB:
+	case UPIO_DWAPB32:
 		if (!up->port.mapbase)
 			break;
 

drivers/serial/serial_core.c

@@ -2135,6 +2135,7 @@ uart_report_port(struct uart_driver *drv, struct uart_port *port)
 	case UPIO_AU:
 	case UPIO_TSI:
 	case UPIO_DWAPB:
+	case UPIO_DWAPB32:
 		snprintf(address, sizeof(address),
 			 "MMIO 0x%llx", (unsigned long long)port->mapbase);
 		break;
@@ -2555,6 +2556,7 @@ int uart_match_port(struct uart_port *port1, struct uart_port *port2)
 	case UPIO_AU:
 	case UPIO_TSI:
 	case UPIO_DWAPB:
+	case UPIO_DWAPB32:
 		return (port1->mapbase == port2->mapbase);
 	}
 	return 0;

include/linux/serial_core.h

@@ -314,6 +314,7 @@ struct uart_port {
 #define UPIO_TSI		(5)			/* Tsi108/109 type IO */
 #define UPIO_DWAPB		(6)			/* DesignWare APB UART */
 #define UPIO_RM9000		(7)			/* RM9000 type IO */
+#define UPIO_DWAPB32		(8)			/* DesignWare APB UART (32 bit accesses) */
 
 	unsigned int		read_status_mask;	/* driver specific */
 	unsigned int		ignore_status_mask;	/* driver specific */