Re: [PATCH] serial: imx: Improve PIO prevention if TX DMA has been started
From: Uwe Kleine-König <hidden>
Date: 2017-08-12 19:54:57
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On Sat, Aug 12, 2017 at 05:12:10PM +0200, Clemens Gruber wrote:
The imx_transmit_buffer function should return if TX DMA has already
been started and not just skip over the buffer PIO write loop. (Which
did fix the initial problem, but could have unintentional side-effects)
Tested on an i.MX6Q board with half-duplex RS-485 and with RS-232.
Cc: Ian Jamison <redacted>
Cc: Uwe-Kleine König <redacted>
Fixes: 514ab34dbad6 ("serial: imx: Prevent TX buffer PIO write when a
DMA has been started")AFAIK no newline in the Fixes: line.
quoted hunk ↗ jump to hunk
Signed-off-by: Clemens Gruber <redacted> --- drivers/tty/serial/imx.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index 80934e7bd67f..fce538eb8c77 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c@@ -452,13 +452,14 @@ static inline void imx_transmit_buffer(struct imx_port *sport) if (sport->dma_is_txing) { temp |= UCR1_TDMAEN; writel(temp, sport->port.membase + UCR1); + return; } else { writel(temp, sport->port.membase + UCR1); imx_dma_tx(sport); }
Shouldn't the return go here? Did you understand the problem? Can you say why this only hurts in RS485 half-duplex but not (as it seems) in regular rs232 mode?
}
- while (!uart_circ_empty(xmit) && !sport->dma_is_txing &&
+ while (!uart_circ_empty(xmit) &&
!(readl(sport->port.membase + uts_reg(sport)) & UTS_TXFULL)) {
/* send xmit->buf[xmit->tail]
* out the port here */Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ |