>From: Greg KH [mailto:gregkh@xxxxxxxxxxxxxxxxxxx] >Sent: Tuesday, March 27, 2012 1:55 PM >Care to resend this without the footer so I can accept it? Sorry. It turns out that the footer was added by our 3rd party email filtering service - I hope that it's no longer being included. On our custom board, we are using RS485 in half-duplex mode on an AT91SAM9G45. SER_RS485_RX_DURING_TX is not set as we do not want to receive the data we transmit (our transceiver will receive transmitted data). Although the current driver attempts to disable and enable the receiver at the appropriate points, incoming data is still loaded into the receive register causing our code to receive the very last byte that was sent once the receiver is enabled. I ran this by Atmel support and they wrote: "The issue comes from the fact that you disable the PDC/DMA Reception and not the USART Reception channel. In your case, the[n] you will still receive data into the USART_RHR register, and maybe you [h]ave the overun flag set. So please disable the USART reception channel." The following patch should force the driver to enable/disable the receiver via RXEN/RXDIS fields of the USART control register. It fixed the issue I was having - perhaps others will find it useful as well. Signed-off-by: Gabe Siftar <gabe.siftar@xxxxxxxxxxxxxx> Index: linux-3.3/drivers/tty/serial/atmel_serial.c =================================================================== --- linux-3.3.orig/drivers/tty/serial/atmel_serial.c +++ linux-3.3/drivers/tty/serial/atmel_serial.c @@ -395,6 +395,8 @@ { UART_PUT_CR(port, ATMEL_US_RSTSTA); /* reset status and receiver */ + UART_PUT_CR(port, ATMEL_US_RXEN); + if (atmel_use_dma_rx(port)) { /* enable PDC controller */ UART_PUT_IER(port, ATMEL_US_ENDRX | ATMEL_US_TIMEOUT | @@ -410,6 +412,8 @@ */ static void atmel_stop_rx(struct uart_port *port) { + UART_PUT_CR(port, ATMEL_US_RXDIS); + if (atmel_use_dma_rx(port)) { /* disable PDC receive */ UART_PUT_PTCR(port, ATMEL_PDC_RXTDIS); -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
