* Mainline commit "serial: Test for no tx data on tx restart" not correct for i.MX6? @ 2014-07-23 4:10 Dirk Behme 2014-07-23 16:32 ` Peter Hurley 0 siblings, 1 reply; 6+ messages in thread From: Dirk Behme @ 2014-07-23 4:10 UTC (permalink / raw) To: linux-serial, Peter Hurley, Huang Shijie Cc: Aaro Koskinen, Greg Kroah-Hartman, Wang, Jiada, Dirk Behme 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? Best regards Dirk P.S.: I don't have the initial post in my inbox, so sorry for the new thread. ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Mainline commit "serial: Test for no tx data on tx restart" not correct for i.MX6? 2014-07-23 4:10 Mainline commit "serial: Test for no tx data on tx restart" not correct for i.MX6? Dirk Behme @ 2014-07-23 16:32 ` Peter Hurley 2014-07-24 8:12 ` jiwang 0 siblings, 1 reply; 6+ messages in thread From: Peter Hurley @ 2014-07-23 16:32 UTC (permalink / raw) To: Dirk Behme, linux-serial, Huang Shijie Cc: Aaro Koskinen, Greg Kroah-Hartman, Wang, Jiada, Dirk Behme 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. Also, the imx driver doesn't send x_char in dma mode? Regards, Peter Hurley ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Mainline commit "serial: Test for no tx data on tx restart" not correct for i.MX6? 2014-07-23 16:32 ` Peter Hurley @ 2014-07-24 8:12 ` jiwang 2014-07-24 11:58 ` Peter Hurley 0 siblings, 1 reply; 6+ messages in thread From: jiwang @ 2014-07-24 8:12 UTC (permalink / raw) To: Peter Hurley, Dirk Behme, linux-serial, Huang Shijie Cc: Aaro Koskinen, Greg Kroah-Hartman, Dirk Behme 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, it only switches tx interrupt on, and tx interrupt does the actual data transfer, so if x_char is pending, it will always be sent before the data in ring buffer. > Also, the imx driver doesn't send x_char in dma mode? Yes, I think so. Thanks, Jiada > Regards, > Peter Hurley > ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Mainline commit "serial: Test for no tx data on tx restart" not correct for i.MX6? 2014-07-24 8:12 ` jiwang @ 2014-07-24 11:58 ` Peter Hurley 2014-07-29 7:18 ` jiwang 0 siblings, 1 reply; 6+ messages in thread From: Peter Hurley @ 2014-07-24 11:58 UTC (permalink / raw) To: jiwang, Dirk Behme, linux-serial, Huang Shijie Cc: Aaro Koskinen, Greg Kroah-Hartman, Dirk Behme 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 } Regards, Peter Hurley ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Mainline commit "serial: Test for no tx data on tx restart" not correct for i.MX6? 2014-07-24 11:58 ` Peter Hurley @ 2014-07-29 7:18 ` jiwang 2014-08-06 23:53 ` Peter Hurley 0 siblings, 1 reply; 6+ messages in thread From: jiwang @ 2014-07-29 7:18 UTC (permalink / raw) To: Peter Hurley, Dirk Behme, linux-serial, Huang Shijie Cc: Aaro Koskinen, Greg Kroah-Hartman, Dirk Behme 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 ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Mainline commit "serial: Test for no tx data on tx restart" not correct for i.MX6? 2014-07-29 7:18 ` jiwang @ 2014-08-06 23:53 ` Peter Hurley 0 siblings, 0 replies; 6+ messages in thread From: Peter Hurley @ 2014-08-06 23:53 UTC (permalink / raw) To: jiwang, Dirk Behme Cc: linux-serial@vger.kernel.org, Huang Shijie, Dirk Behme, Greg Kroah-Hartman 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@hurleysoftware.com> --- 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 ^ permalink raw reply related [flat|nested] 6+ messages in thread
end of thread, other threads:[~2014-08-06 23:54 UTC | newest] Thread overview: 6+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2014-07-23 4:10 Mainline commit "serial: Test for no tx data on tx restart" not correct for i.MX6? Dirk Behme 2014-07-23 16:32 ` Peter Hurley 2014-07-24 8:12 ` jiwang 2014-07-24 11:58 ` Peter Hurley 2014-07-29 7:18 ` jiwang 2014-08-06 23:53 ` Peter Hurley
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