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: Jamie Iles <jamie@jamieiles.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 41 insertions, 12 deletions

diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 0b4ce47d9871..9839199c1d1d 100644
--- a/drivers/serial/8250.c
+++ b/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);
 }
 
+/* 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)
+{
+        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;
-        /* 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);
-                up->lcr = value;
-        }
+        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;
 
diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
index c4ea14670d44..2835e29298ed 100644
--- a/drivers/serial/serial_core.c
+++ b/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;