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OMAP/serial: Fix incorrect Rx FIFO threshold setting, LSR validation on Tx, and Tx FIFO IRQ generation

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Original configuration of Rx FIFO threshold contained an error
that resulted Rx threshold to be effectively set to 1 character
instead of 16 characters, as noted in comments.
Checking LSR to contain UART_LSR_THRE bit set caused issue when
not all UART_IER_THRI interrupts have been properly handled.
This caused gap in Tx data, visible on high baud rates using
oscilloscope.
Setting OMAP_UART_SCR_TX_EMPTY bit in SCR caused UART_IER_THRI
interrupt to be raised only when Tx FIFO and Tx shift registers
are empty.

Signed-off-by: Alexey Pelykh <alexey.pelykh@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Alexey Pelykh 2013-02-04 12:19:46 -05:00 committed by Greg Kroah-Hartman
parent f26402e817
commit 1776fd059c
1 changed files with 2 additions and 6 deletions
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8
drivers/tty/serial/omap-serial.c
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@ -59,6 +59,7 @@
/* SCR register bitmasks */
#define OMAP_UART_SCR_RX_TRIG_GRANU1_MASK (1 << 7)
#define OMAP_UART_SCR_TX_TRIG_GRANU1_MASK (1 << 6)
#define OMAP_UART_SCR_TX_EMPTY (1 << 3)
/* FCR register bitmasks */
@ -320,9 +321,6 @@ static void transmit_chars(struct uart_omap_port *up, unsigned int lsr)
struct circ_buf *xmit = &up->port.state->xmit;
int count;
if (!(lsr & UART_LSR_THRE))
return;
if (up->port.x_char) {
serial_out(up, UART_TX, up->port.x_char);
up->port.icount.tx++;
@ -864,7 +862,7 @@ serial_omap_set_termios(struct uart_port *port, struct ktermios *termios,
serial_out(up, UART_IER, up->ier);
serial_out(up, UART_LCR, cval); /* reset DLAB */
up->lcr = cval;
up->scr = OMAP_UART_SCR_TX_EMPTY;
up->scr = 0;
/* FIFOs and DMA Settings */
@ -888,8 +886,6 @@ serial_omap_set_termios(struct uart_port *port, struct ktermios *termios,
serial_out(up, UART_MCR, up->mcr | UART_MCR_TCRTLR);
/* FIFO ENABLE, DMA MODE */
up->scr |= OMAP_UART_SCR_RX_TRIG_GRANU1_MASK;
/* Set receive FIFO threshold to 16 characters and
* transmit FIFO threshold to 16 spaces
*/