Hi Peter
On 07/24/2014 08:58 PM, Peter Hurley wrote:
Hi Jiada,
On 07/24/2014 04:12 AM, jiwang wrote:
Hi Peter
On 07/24/2014 01:32 AM, Peter Hurley wrote:
Hi Dirk,
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?
Thanks for the comment.
Yeah, I missed that the imx driver handled x_char _at all_,
because how the imx driver is handling x_char looks broken.
For example, if data is already in the tx ring buffer,
imx_start_tx() will send that data before the x_char, and if
all the tx ring buffer data is sent successfully, the tx
interrupt is switched back off, so the x_char won't be sent.
imx_start_tx() doesn't do any actual data transfer
???
565 static void imx_start_tx(struct uart_port *port)
566 {
...
610
611 if (readl(sport->port.membase + uts_reg(sport)) & UTS_TXEMPTY)
612 imx_transmit_buffer(sport);
613 }
463 static inline void imx_transmit_buffer(struct imx_port *sport)
464 {
465 struct circ_buf *xmit = &sport->port.state->xmit;
466
467 while (!uart_circ_empty(xmit) &&
468 !(readl(sport->port.membase + uts_reg(sport))
469 & UTS_TXFULL)) {
470 /* send xmit->buf[xmit->tail]
471 * out the port here */
472 writel(xmit->buf[xmit->tail], sport->port.membase + URTX0);
473 xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
474 sport->port.icount.tx++;
475 }
476
477 if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
478 uart_write_wakeup(&sport->port);
479
480 if (uart_circ_empty(xmit))
481 imx_stop_tx(&sport->port);
482 }
sorry, our imx driver has been modified differently,
yes, you are right, mainline imx driver's handling of x_char looks broken
@Shijie,
do you have any comment?
Thanks,
Jiada
Regards,
Peter Hurley
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