serial: mfd: remove the TX full-empty interrupts workaround

In A0 stepping, TX half-empty interrupt is not working, so have to
use the full-empty interrupts whose performance will be 15% lower.
Now re-enable the half-empty interrrupt after it is enabled in
silicon.

Signed-off-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 5 insertions, 21 deletions

diff --git a/drivers/tty/serial/mfd.c b/drivers/tty/serial/mfd.c
index 776777462937..53ff6af16273 100644
--- a/drivers/tty/serial/mfd.c
+++ b/drivers/tty/serial/mfd.c
@@ -16,9 +16,7 @@
  *    2/3 chan to port 1, 4/5 chan to port 3. Even number chans
  *    are used for RX, odd chans for TX
  *
- * 2. In A0 stepping, UART will not support TX half empty flag
- *
- * 3. The RI/DSR/DCD/DTR are not pinned out, DCD & DSR are always
+ * 2. The RI/DSR/DCD/DTR are not pinned out, DCD & DSR are always
  *    asserted, only when the HW is reset the DDCD and DDSR will
  *    be triggered
  */
@@ -41,8 +39,6 @@
 #include <linux/io.h>
 #include <linux/debugfs.h>
 
-#define  MFD_HSU_A0_STEPPING    1
-
 #define HSU_DMA_BUF_SIZE        2048
 
 #define chan_readl(chan, offset)        readl(chan->reg + offset)
@@ -543,16 +539,9 @@ static void transmit_chars(struct uart_hsu_port *up)
                 return;
         }
 
-#ifndef MFD_HSU_A0_STEPPING
+        /* The IRQ is for TX FIFO half-empty */
         count = up->port.fifosize / 2;
-#else
-        /*
-         * A0 only supports fully empty IRQ, and the first char written
-         * into it won't clear the EMPT bit, so we may need be cautious
-         * by useing a shorter buffer
-         */
-        count = up->port.fifosize - 4;
-#endif
+
         do {
                 serial_out(up, UART_TX, xmit->buf[xmit->tail]);
                 xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
@@ -761,9 +750,8 @@ static void serial_hsu_break_ctl(struct uart_port *port, int break_state)
 /*
  * What special to do:
  * 1. chose the 64B fifo mode
- * 2. make sure not to select half empty mode for A0 stepping
- * 3. start dma or pio depends on configuration
- * 4. we only allocate dma memory when needed
+ * 2. start dma or pio depends on configuration
+ * 3. we only allocate dma memory when needed
  */
 static int serial_hsu_startup(struct uart_port *port)
 {
@@ -967,10 +955,6 @@ serial_hsu_set_termios(struct uart_port *port, struct ktermios *termios,
                 fcr = UART_FCR_ENABLE_FIFO | UART_FCR_HSU_64_32B;
 
         fcr |= UART_FCR_HSU_64B_FIFO;
-#ifdef MFD_HSU_A0_STEPPING
-        /* A0 doesn't support half empty IRQ */
-        fcr |= UART_FCR_FULL_EMPT_TXI;
-#endif
 
         /*
          * Ok, we're now changing the port state.  Do it with