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serial: 8250_mxpcie: speed up TX using memory-mapped FIFO window

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The MUEx50 UART provides a memory-mapped TX FIFO data window along with
a TX FIFO level counter.

Fill the TX FIFO in bulk via the MMIO FIFO window based on available
FIFO space, using uart_port_tx_limited() for the common serial-core TX
handling.

Signed-off-by: Crescent Hsieh <crescentcy.hsieh@moxa.com>
Link: https://patch.msgid.link/20260731074820.735619-9-crescentcy.hsieh@moxa.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Crescent Hsieh 2026-07-31 15:48:14 +08:00 committed by Greg Kroah-Hartman
parent c016f2405c
commit 7df53c4d33
1 changed files with 15 additions and 1 deletions
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16
drivers/tty/serial/8250/8250_mxpcie.c
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@ -81,8 +81,10 @@
#define MOXA_PUART_FCL 0x12 /* Flow Control Low Trigger Level */
#define MOXA_PUART_FCH 0x13 /* Flow Control High Trigger Level */
#define MOXA_PUART_RX_FIFO_CNT 0x15 /* Rx FIFO Data Counter */
#define MOXA_PUART_TX_FIFO_CNT 0x16 /* Tx FIFO Data Counter */
#define MOXA_PUART_RX_FIFO_MEM 0x100 /* Memory Space to Rx FIFO Data Register */
#define MOXA_PUART_TX_FIFO_MEM 0x100 /* Memory Space to Tx FIFO Data Register */
#define MOXA_GPIO_DIRECTION 0x09
#define MOXA_GPIO_OUTPUT 0x0A
@ -304,6 +306,18 @@ static bool mxpcie8250_should_rx(struct uart_8250_port *up, u16 lsr)
return false;
}
static void mxpcie8250_tx_chars(struct uart_8250_port *up)
{
struct uart_port *port = &up->port;
unsigned int offset = 0;
unsigned char c;
uart_port_tx_limited(port, c, port->fifosize - serial_in(up, MOXA_PUART_TX_FIFO_CNT),
true,
serial_out(up, MOXA_PUART_TX_FIFO_MEM + offset++, c),
({}));
}
static int mxpcie8250_handle_irq(struct uart_port *port)
{
struct uart_8250_port *up = up_to_u8250p(port);
@ -327,7 +341,7 @@ static int mxpcie8250_handle_irq(struct uart_port *port)
serial8250_modem_status(up);
if ((lsr & UART_LSR_THRE) && (up->ier & UART_IER_THRI))
serial8250_tx_chars(up);
mxpcie8250_tx_chars(up);
return 1;
}