Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1389070

[PATCH v3 07/11] serial: 8250: enable AFE on ports where FIFO is 16 bytes

Show all headers | View raw

Intel Quark has 16550A compatible UART with autoflow feature enabled. It has
only 16 bytes of FIFO. Currently serial8250_do_set_termios() prevents to enable
autoflow since the minimum requirement of 32 bytes of FIFO size.

Drop a FIFO size limitation to allow autoflow control be enabled on such UARTs.

While here, comment out UART_CAP_AFE for PORT_AR7 since it wasn't working and
it will be not a good idea to use it in conjunction with trigger level of 1
byte.

Suggested-by: Peter Hurley <peter@hurleysoftware.com>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/tty/serial/8250/8250_port.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 00ad263..719a561 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -178,7 +178,7 @@ static const struct serial8250_config uart_config[] = {
 		.fifo_size	= 16,
 		.tx_loadsz	= 16,
 		.fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_00,
-		.flags		= UART_CAP_FIFO | UART_CAP_AFE,
+		.flags		= UART_CAP_FIFO /* | UART_CAP_AFE */,
 	},
 	[PORT_U6_16550A] = {
 		.name		= "U6_16550A",
@@ -2528,12 +2528,9 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
 	/*
 	 * MCR-based auto flow control.  When AFE is enabled, RTS will be
 	 * deasserted when the receive FIFO contains more characters than
-	 * the trigger, or the MCR RTS bit is cleared.  In the case where
-	 * the remote UART is not using CTS auto flow control, we must
-	 * have sufficient FIFO entries for the latency of the remote
-	 * UART to respond.  IOW, at least 32 bytes of FIFO.
+	 * the trigger, or the MCR RTS bit is cleared.
 	 */
-	if (up->capabilities & UART_CAP_AFE && port->fifosize >= 32) {
+	if (up->capabilities & UART_CAP_AFE) {
 		up->mcr &= ~UART_MCR_AFE;
 		if (termios->c_cflag & CRTSCTS)
 			up->mcr |= UART_MCR_AFE;
-- 
2.8.0.rc3

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH v3 00/11] serial: 8250: split LPSS to 8250_lpss, enable DMA on Quark Andy Shevchenko <andriy.shevchenko@linux.intel.com> - 2016-04-27 15:50 +0200
  [PATCH v3 07/11] serial: 8250: enable AFE on ports where FIFO is 16 bytes Andy Shevchenko <andriy.shevchenko@linux.intel.com> - 2016-04-27 15:50 +0200
  [PATCH v3 04/11] dmaengine: dw: override LLP support if asked in platform data Andy Shevchenko <andriy.shevchenko@linux.intel.com> - 2016-04-27 15:50 +0200
  [PATCH v3 01/11] dmaengine: dw: keep copy of custom slave config in dwc Andy Shevchenko <andriy.shevchenko@linux.intel.com> - 2016-04-27 16:00 +0200
  [PATCH v3 06/11] serial: 8250_dma: adjust DMA address of the UART Andy Shevchenko <andriy.shevchenko@linux.intel.com> - 2016-04-27 16:00 +0200
  [PATCH v3 10/11] serial: 8250_lpss: enable MSI for Intel Quark Andy Shevchenko <andriy.shevchenko@linux.intel.com> - 2016-04-27 16:00 +0200
  [PATCH v3 11/11] serial: 8250_lpss: enable DMA on Intel Quark UART Andy Shevchenko <andriy.shevchenko@linux.intel.com> - 2016-04-27 16:00 +0200

csiph-web