tty: serial: OMAP: ensure FIFO levels are set correctly in non-DMA mode

Ensure FIFO levels are set correctly in non-DMA mode (the default).
This patch will cause a receive FIFO threshold interrupt to be raised when
there is at least one byte in the RX FIFO.  It will also cause a transmit
FIFO threshold interrupt when there is only one byte remaining in the TX
FIFO.

These changes fix the receive interrupt problem and part of the
transmit interrupt problem.  A separate set of issues must be worked
around for the transmit path to have a basic level of functionality; a
subsequent patch will address these.

DMA operation is unaffected by this patch.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Govindraj Raja <govindraj.r@ti.com>
Cc: Kevin Hilman <khilman@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 31 insertions, 4 deletions

diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
index 1c2426931484..ca54f038ab45 100644
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -46,6 +46,18 @@
 
 #define DEFAULT_CLK_SPEED 48000000 /* 48Mhz*/
 
+/* SCR register bitmasks */
+#define OMAP_UART_SCR_RX_TRIG_GRANU1_MASK               (1 << 7)
+#define OMAP_UART_SCR_TX_TRIG_GRANU1_MASK               (1 << 6)
+
+/* FCR register bitmasks */
+#define OMAP_UART_FCR_RX_FIFO_TRIG_SHIFT                6
+#define OMAP_UART_FCR_RX_FIFO_TRIG_MASK                 (0x3 << 6)
+#define OMAP_UART_FCR_TX_FIFO_TRIG_SHIFT                4
+
+/* TLR register bitmasks */
+#define OMAP_UART_TLR_TX_FIFO_TRIG_DMA_SHIFT            0
+
 static struct uart_omap_port *ui[OMAP_MAX_HSUART_PORTS];
 
 /* Forward declaration of functions */
@@ -694,6 +706,7 @@ serial_omap_set_termios(struct uart_port *port, struct ktermios *termios,
         unsigned char efr = 0;
         unsigned long flags = 0;
         unsigned int baud, quot;
+        u32 tlr;
 
         switch (termios->c_cflag & CSIZE) {
         case CS5:
@@ -811,14 +824,28 @@ serial_omap_set_termios(struct uart_port *port, struct ktermios *termios,
         up->mcr = serial_in(up, UART_MCR);
         serial_out(up, UART_MCR, up->mcr | UART_MCR_TCRTLR);
         /* FIFO ENABLE, DMA MODE */
-        serial_out(up, UART_FCR, up->fcr);
-        serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
+
+        up->scr |= OMAP_UART_SCR_TX_TRIG_GRANU1_MASK;
+        up->scr |= OMAP_UART_SCR_RX_TRIG_GRANU1_MASK;
 
         if (up->use_dma) {
-                serial_out(up, UART_TI752_TLR, 0);
-                up->scr |= (UART_FCR_TRIGGER_4 | UART_FCR_TRIGGER_8);
+                tlr = 0;
+        } else {
+                up->scr &= ~OMAP_UART_SCR_TX_EMPTY;
+
+                /* Set receive FIFO threshold to 1 */
+                up->fcr &= ~OMAP_UART_FCR_RX_FIFO_TRIG_MASK;
+                up->fcr |= (0x1 << OMAP_UART_FCR_RX_FIFO_TRIG_SHIFT);
+
+                /* Set TX FIFO threshold to "63" (actually 1) */
+                up->fcr |= (0x3 << OMAP_UART_FCR_TX_FIFO_TRIG_SHIFT);
+                tlr = (0xf << OMAP_UART_TLR_TX_FIFO_TRIG_DMA_SHIFT);
         }
 
+        serial_out(up, UART_TI752_TLR, tlr);
+        serial_out(up, UART_FCR, up->fcr);
+        serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
+
         serial_out(up, UART_OMAP_SCR, up->scr);
 
         serial_out(up, UART_EFR, up->efr);