From: Marc Pignat Strange chars appear on the serial port when a printk and a printf happens at the same time. This is caused by the pdc sending chars while atmel_console_write (called from printk) is executing Concurent access of uart and console to the same port leads to corrupted data to be transmitted, so disable tx dma (PDC) while writing to the console. Signed-off-by: Marc Pignat Signed-off-by: Haavard Skinnemoen Signed-off-by: Andrew Morton --- drivers/serial/atmel_serial.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff -puN drivers/serial/atmel_serial.c~atmel_serial-fix-uart-console-concurrent-access drivers/serial/atmel_serial.c --- a/drivers/serial/atmel_serial.c~atmel_serial-fix-uart-console-concurrent-access +++ a/drivers/serial/atmel_serial.c @@ -107,6 +107,7 @@ #define UART_PUT_TPR(port,v) __raw_writel(v, (port)->membase + ATMEL_PDC_TPR) #define UART_PUT_TCR(port,v) __raw_writel(v, (port)->membase + ATMEL_PDC_TCR) +#define UART_GET_TCR(port) __raw_readl((port)->membase + ATMEL_PDC_TCR) static int (*atmel_open_hook)(struct uart_port *); static void (*atmel_close_hook)(struct uart_port *); @@ -1275,6 +1276,7 @@ static void atmel_console_write(struct c { struct uart_port *port = &atmel_ports[co->index].uart; unsigned int status, imr; + unsigned int pdc_tx; /* * First, save IMR and then disable interrupts @@ -1282,6 +1284,10 @@ static void atmel_console_write(struct c imr = UART_GET_IMR(port); UART_PUT_IDR(port, ATMEL_US_RXRDY | ATMEL_US_TXRDY); + /* Store PDC transmit status and disable it */ + pdc_tx = UART_GET_PTSR(port) & ATMEL_PDC_TXTEN; + UART_PUT_PTCR(port, ATMEL_PDC_TXTDIS); + uart_console_write(port, s, count, atmel_console_putchar); /* @@ -1291,6 +1297,11 @@ static void atmel_console_write(struct c do { status = UART_GET_CSR(port); } while (!(status & ATMEL_US_TXRDY)); + + /* Restore PDC transmit status */ + if (pdc_tx) + UART_PUT_PTCR(port, ATMEL_PDC_TXTEN); + /* set interrupts back the way they were */ UART_PUT_IER(port, imr); } _