From: Michael Trimarchi Date: Wed, 2 Apr 2008 20:04:41 +0000 (-0700) Subject: atmel_serial: avoid stopping pdc during transmission X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=ba0657ff0527bab83387e19eb98b423fcc290674;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git atmel_serial: avoid stopping pdc during transmission I found a problem related to losing data during pdc transmission in atmel_serial: connect ttyS1 with ttyS2 using a loopback cable, send 30 byte of packet from one to the other and waiting for 30 byte. On the other side just read and echo the data received. We always call atmel_tx_dma() from the tasklet regardless of what interrupt triggered it. Signed-off-by: michael Acked-by: Haavard Skinnemoen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/drivers/serial/atmel_serial.c b/drivers/serial/atmel_serial.c index d57bf3e708d8..e99a28387505 100644 --- a/drivers/serial/atmel_serial.c +++ b/drivers/serial/atmel_serial.c @@ -96,6 +96,7 @@ /* PDC registers */ #define UART_PUT_PTCR(port,v) __raw_writel(v, (port)->membase + ATMEL_PDC_PTCR) +#define UART_GET_TCR(port) __raw_readl((port)->membase + ATMEL_PDC_TCR) #define UART_GET_PTSR(port) __raw_readl((port)->membase + ATMEL_PDC_PTSR) #define UART_PUT_RPR(port,v) __raw_writel(v, (port)->membase + ATMEL_PDC_RPR) @@ -562,17 +563,22 @@ static void atmel_tx_dma(struct uart_port *port) struct atmel_dma_buffer *pdc = &atmel_port->pdc_tx; int count; + /* nothing left to transmit? */ + if (UART_GET_TCR(port)) + return; + xmit->tail += pdc->ofs; xmit->tail &= UART_XMIT_SIZE - 1; port->icount.tx += pdc->ofs; pdc->ofs = 0; - if (!uart_circ_empty(xmit)) { - /* more to transmit - setup next transfer */ + /* more to transmit - setup next transfer */ - /* disable PDC transmit */ - UART_PUT_PTCR(port, ATMEL_PDC_TXTDIS); + /* disable PDC transmit */ + UART_PUT_PTCR(port, ATMEL_PDC_TXTDIS); + + if (!uart_circ_empty(xmit)) { dma_sync_single_for_device(port->dev, pdc->dma_addr, pdc->dma_size, @@ -586,11 +592,6 @@ static void atmel_tx_dma(struct uart_port *port) /* re-enable PDC transmit and interrupts */ UART_PUT_PTCR(port, ATMEL_PDC_TXTEN); UART_PUT_IER(port, ATMEL_US_ENDTX | ATMEL_US_TXBUFE); - } else { - /* nothing left to transmit - disable the transmitter */ - - /* disable PDC transmit */ - UART_PUT_PTCR(port, ATMEL_PDC_TXTDIS); } if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)