On 07/29/2014 03:18 AM, jiwang wrote: > On 07/24/2014 08:58 PM, Peter Hurley wrote: >> On 07/24/2014 04:12 AM, jiwang wrote: >>> On 07/24/2014 01:32 AM, Peter Hurley wrote: >>>> On 07/23/2014 12:10 AM, Dirk Behme wrote: >>>>> Hi, >>>>> >>>>> this is a question regarding the i.MX6 part (drivers/tty/serial/imx.c) of the commit >>>>> >>>>> serial: Test for no tx data on tx restart >>>>> >>>>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=c557d392fbf5badd693ea1946a4317c87a26a716 >>>>> >>>>> Talking with some i.MX6 experts about this, I've got the comment >>>>> >>>>> -- cut -- >>>>> The imx serial driver part of this commit isn't correct >>>>> as imx.c sends x_char in irq handler, not in imx_start_tx(), >>>>> -- cut -- >>>>> >>>>> What do you think? >>>> >>>> Yeah, I missed that the imx driver handled x_char _at all_, >>>> because how the imx driver is handling x_char looks broken. [...] > sorry, our imx driver has been modified differently, > yes, you are right, mainline imx driver's handling of x_char looks broken Jiada or Dirk or whomever, Would someone please test the patch below on actual imx hardware? You can download a standalone x_char unit test from http://blog.hurleysoftware.com/uploads/tty_xchar.c Instructions for building, setting up and testing are included in the file. --- >% --- Subject: [PATCH] serial: imx: Fix x_char handling and tx flow control The serial core expects the UART driver to transmit x_char (START/STOP chars) even if tx is stopped and before data already in the tx ring buffer if possible. Also, sending x_char must not cause additional data in the tx ring buffer to transmit if tx is stopped. Cause x_char to be transmitted before any other data is sent. Auto-stop tx if the tx ring buffer is empty or tx should be stopped. Only perform one write wakeup if tx ring buffer space is below threshold. x_char handling in DMA mode is still broken; add FIXME. Signed-off-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx> --- drivers/tty/serial/imx.c | 39 ++++++++++++++++----------------------- 1 file changed, 16 insertions(+), 23 deletions(-) diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index be1c842..00a37e9 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -460,9 +460,19 @@ static inline void imx_transmit_buffer(struct imx_port *sport) { struct circ_buf *xmit = &sport->port.state->xmit; + if (sport->port.x_char) { + /* Send next char */ + writel(sport->port.x_char, sport->port.membase + URTX0); + return; + } + + if (uart_circ_empty(xmit) || uart_tx_stopped(&sport->port)) { + imx_stop_tx(&sport->port); + return; + } + while (!uart_circ_empty(xmit) && - !(readl(sport->port.membase + uts_reg(sport)) - & UTS_TXFULL)) { + !(readl(sport->port.membase + uts_reg(sport)) & UTS_TXFULL)) { /* send xmit->buf[xmit->tail] * out the port here */ writel(xmit->buf[xmit->tail], sport->port.membase + URTX0); @@ -563,9 +573,6 @@ static void imx_start_tx(struct uart_port *port) struct imx_port *sport = (struct imx_port *)port; unsigned long temp; - if (uart_circ_empty(&port->state->xmit)) - return; - if (USE_IRDA(sport)) { /* half duplex in IrDA mode; have to disable receive mode */ temp = readl(sport->port.membase + UCR4); @@ -600,7 +607,10 @@ static void imx_start_tx(struct uart_port *port) } if (sport->dma_is_enabled) { - imx_dma_tx(sport); + /* FIXME: port->x_char must be transmitted if != 0 */ + if (!uart_circ_empty(&port->state->xmit) && + !uart_tx_stopped(port)) + imx_dma_tx(sport); return; } @@ -628,27 +638,10 @@ static irqreturn_t imx_rtsint(int irq, void *dev_id) static irqreturn_t imx_txint(int irq, void *dev_id) { struct imx_port *sport = dev_id; - struct circ_buf *xmit = &sport->port.state->xmit; unsigned long flags; spin_lock_irqsave(&sport->port.lock, flags); - if (sport->port.x_char) { - /* Send next char */ - writel(sport->port.x_char, sport->port.membase + URTX0); - goto out; - } - - if (uart_circ_empty(xmit) || uart_tx_stopped(&sport->port)) { - imx_stop_tx(&sport->port); - goto out; - } - imx_transmit_buffer(sport); - - if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS) - uart_write_wakeup(&sport->port); - -out: spin_unlock_irqrestore(&sport->port.lock, flags); return IRQ_HANDLED; } -- 2.0.4 -- 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
