msm_serial: Send more than 1 character at a time on UARTDM

UARTDM cores have a TX fifo that can accept more than one
character per register write, but the msm_serial driver currently
only supports 1 character mode. Add support for this mode of operation
to speed up the transmit path on DM devices.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Acked-by: David Brown <davidb@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 32 insertions, 19 deletions

diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c
index ca2ae6581149..252d514b47fb 100644
--- a/drivers/tty/serial/msm_serial.c
+++ b/drivers/tty/serial/msm_serial.c
@@ -195,10 +195,10 @@ static void handle_rx(struct uart_port *port)
         tty_flip_buffer_push(tport);
 }
 
-static void reset_dm_count(struct uart_port *port)
+static void reset_dm_count(struct uart_port *port, int count)
 {
         wait_for_xmitr(port);
-        msm_write(port, 1, UARTDM_NCF_TX);
+        msm_write(port, count, UARTDM_NCF_TX);
         msm_read(port, UARTDM_NCF_TX);
 }
 
@@ -206,39 +206,52 @@ static void handle_tx(struct uart_port *port)
 {
         struct circ_buf *xmit = &port->state->xmit;
         struct msm_port *msm_port = UART_TO_MSM(port);
-        int sent_tx;
+        unsigned int tx_count, num_chars;
+        unsigned int tf_pointer = 0;
+
+        tx_count = uart_circ_chars_pending(xmit);
+        tx_count = min3(tx_count, (unsigned int)UART_XMIT_SIZE - xmit->tail,
+                        port->fifosize);
 
         if (port->x_char) {
                 if (msm_port->is_uartdm)
-                        reset_dm_count(port);
+                        reset_dm_count(port, tx_count + 1);
 
                 msm_write(port, port->x_char,
                           msm_port->is_uartdm ? UARTDM_TF : UART_TF);
                 port->icount.tx++;
                 port->x_char = 0;
+        } else if (tx_count && msm_port->is_uartdm) {
+                reset_dm_count(port, tx_count);
         }
 
-        if (msm_port->is_uartdm)
-                reset_dm_count(port);
+        while (tf_pointer < tx_count) {
+                int i;
+                char buf[4] = { 0 };
+                unsigned int *bf = (unsigned int *)&buf;
 
-        while (msm_read(port, UART_SR) & UART_SR_TX_READY) {
-                if (uart_circ_empty(xmit)) {
-                        /* disable tx interrupts */
-                        msm_port->imr &= ~UART_IMR_TXLEV;
-                        msm_write(port, msm_port->imr, UART_IMR);
+                if (!(msm_read(port, UART_SR) & UART_SR_TX_READY))
                         break;
-                }
-                msm_write(port, xmit->buf[xmit->tail],
-                          msm_port->is_uartdm ? UARTDM_TF : UART_TF);
 
                 if (msm_port->is_uartdm)
-                        reset_dm_count(port);
+                        num_chars = min(tx_count - tf_pointer, sizeof(buf));
+                else
+                        num_chars = 1;
 
-                xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
-                port->icount.tx++;
-                sent_tx = 1;
+                for (i = 0; i < num_chars; i++) {
+                        buf[i] = xmit->buf[xmit->tail + i];
+                        port->icount.tx++;
+                }
+
+                msm_write(port, *bf, msm_port->is_uartdm ? UARTDM_TF : UART_TF);
+                xmit->tail = (xmit->tail + num_chars) & (UART_XMIT_SIZE - 1);
+                tf_pointer += num_chars;
         }
 
+        /* disable tx interrupts if nothing more to send */
+        if (uart_circ_empty(xmit))
+                msm_stop_tx(port);
+
         if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
                 uart_write_wakeup(port);
 }
@@ -759,7 +772,7 @@ static void msm_console_putchar(struct uart_port *port, int c)
         struct msm_port *msm_port = UART_TO_MSM(port);
 
         if (msm_port->is_uartdm)
-                reset_dm_count(port);
+                reset_dm_count(port, 1);
 
         while (!(msm_read(port, UART_SR) & UART_SR_TX_READY))
                 ;