drivers/tty/serial/xilinx_uartps.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-)
RTS line control with delay should be triggered when there is no more bytes
in kfifo and hardware buffer is empty. Without this patch RTS control is
scheduled right after feeding hardware buffer and this is too early.
RTS line may change state before hardware buffer is empty.
With this patch delayed RTS state change is triggered when function
cdns_uart_handle_tx is called from cdns_uart_isr on CDNS_UART_IXR_TXEMPTY
exactly when hardware completed transmission
Signed-off-by: Jakub Turek <jakub.turek@elsta.tech>
Fixes: fccc9d9233f9 ("tty: serial: uartps: Add rs485 support to uartps driver")
---
drivers/tty/serial/xilinx_uartps.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)
diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index 1e4d54fd5762..923a8b57ec82 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -432,6 +432,12 @@ static void cdns_uart_handle_tx(void *dev_id)
if (kfifo_is_empty(&tport->xmit_fifo) || uart_tx_stopped(port)) {
/* Disable the TX Empty interrupt */
writel(CDNS_UART_IXR_TXEMPTY, port->membase + CDNS_UART_IDR);
+ /* Set RTS line after delay */
+ if (cdns_uart->port->rs485.flags & SER_RS485_ENABLED) {
+ cdns_uart->tx_timer.function = &cdns_rs485_rx_callback;
+ rts_delay = ns_to_ktime(cdns_calc_after_tx_delay(cdns_uart));
+ hrtimer_start(&cdns_uart->tx_timer, rts_delay, HRTIMER_MODE_REL);
+ }
return;
}
@@ -448,13 +454,6 @@ static void cdns_uart_handle_tx(void *dev_id)
/* Enable the TX Empty interrupt */
writel(CDNS_UART_IXR_TXEMPTY, cdns_uart->port->membase + CDNS_UART_IER);
-
- if (cdns_uart->port->rs485.flags & SER_RS485_ENABLED &&
- (kfifo_is_empty(&tport->xmit_fifo) || uart_tx_stopped(port))) {
- hrtimer_update_function(&cdns_uart->tx_timer, cdns_rs485_rx_callback);
- hrtimer_start(&cdns_uart->tx_timer,
- ns_to_ktime(cdns_calc_after_tx_delay(cdns_uart)), HRTIMER_MODE_REL);
- }
}
/**
--
2.34.1Hi j.turek,
kernel test robot noticed the following build errors:
[auto build test ERROR on tty/tty-testing]
[also build test ERROR on tty/tty-next tty/tty-linus usb/usb-testing usb/usb-next usb/usb-linus linus/master v6.19-rc1 next-20251219]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/j-turek/serial-xilinx_uartps-fix-rs485-delay_rts_after_send/20251219-203016
base: https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git tty-testing
patch link: https://lore.kernel.org/r/20251219114826.135017-1-jakub.turek%40elsta.tech
patch subject: [PATCH] serial: xilinx_uartps: fix rs485 delay_rts_after_send
config: sh-allmodconfig (https://download.01.org/0day-ci/archive/20251220/202512202222.7nCGPOv4-lkp@intel.com/config)
compiler: sh4-linux-gcc (GCC) 15.1.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251220/202512202222.7nCGPOv4-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202512202222.7nCGPOv4-lkp@intel.com/
All errors (new ones prefixed by >>):
drivers/tty/serial/xilinx_uartps.c: In function 'cdns_uart_handle_tx':
>> drivers/tty/serial/xilinx_uartps.c:438:25: error: 'rts_delay' undeclared (first use in this function)
438 | rts_delay = ns_to_ktime(cdns_calc_after_tx_delay(cdns_uart));
| ^~~~~~~~~
drivers/tty/serial/xilinx_uartps.c:438:25: note: each undeclared identifier is reported only once for each function it appears in
vim +/rts_delay +438 drivers/tty/serial/xilinx_uartps.c
418
419 /**
420 * cdns_uart_handle_tx - Handle the bytes to be transmitted.
421 * @dev_id: Id of the UART port
422 * Return: None
423 */
424 static void cdns_uart_handle_tx(void *dev_id)
425 {
426 struct uart_port *port = (struct uart_port *)dev_id;
427 struct cdns_uart *cdns_uart = port->private_data;
428 struct tty_port *tport = &port->state->port;
429 unsigned int numbytes;
430 unsigned char ch;
431
432 if (kfifo_is_empty(&tport->xmit_fifo) || uart_tx_stopped(port)) {
433 /* Disable the TX Empty interrupt */
434 writel(CDNS_UART_IXR_TXEMPTY, port->membase + CDNS_UART_IDR);
435 /* Set RTS line after delay */
436 if (cdns_uart->port->rs485.flags & SER_RS485_ENABLED) {
437 cdns_uart->tx_timer.function = &cdns_rs485_rx_callback;
> 438 rts_delay = ns_to_ktime(cdns_calc_after_tx_delay(cdns_uart));
439 hrtimer_start(&cdns_uart->tx_timer, rts_delay, HRTIMER_MODE_REL);
440 }
441 return;
442 }
443
444 numbytes = port->fifosize;
445 while (numbytes &&
446 !(readl(port->membase + CDNS_UART_SR) & CDNS_UART_SR_TXFULL) &&
447 uart_fifo_get(port, &ch)) {
448 writel(ch, port->membase + CDNS_UART_FIFO);
449 numbytes--;
450 }
451
452 if (kfifo_len(&tport->xmit_fifo) < WAKEUP_CHARS)
453 uart_write_wakeup(port);
454
455 /* Enable the TX Empty interrupt */
456 writel(CDNS_UART_IXR_TXEMPTY, cdns_uart->port->membase + CDNS_UART_IER);
457 }
458
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
Hi j.turek,
kernel test robot noticed the following build errors:
[auto build test ERROR on tty/tty-testing]
[also build test ERROR on tty/tty-next tty/tty-linus usb/usb-testing usb/usb-next usb/usb-linus linus/master v6.19-rc1 next-20251219]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/j-turek/serial-xilinx_uartps-fix-rs485-delay_rts_after_send/20251219-203016
base: https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git tty-testing
patch link: https://lore.kernel.org/r/20251219114826.135017-1-jakub.turek%40elsta.tech
patch subject: [PATCH] serial: xilinx_uartps: fix rs485 delay_rts_after_send
config: hexagon-allmodconfig (https://download.01.org/0day-ci/archive/20251220/202512202351.ovK2vDUR-lkp@intel.com/config)
compiler: clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251220/202512202351.ovK2vDUR-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202512202351.ovK2vDUR-lkp@intel.com/
All errors (new ones prefixed by >>):
>> drivers/tty/serial/xilinx_uartps.c:438:4: error: use of undeclared identifier 'rts_delay'
438 | rts_delay = ns_to_ktime(cdns_calc_after_tx_delay(cdns_uart));
| ^
drivers/tty/serial/xilinx_uartps.c:439:40: error: use of undeclared identifier 'rts_delay'; did you mean '__delay'?
439 | hrtimer_start(&cdns_uart->tx_timer, rts_delay, HRTIMER_MODE_REL);
| ^~~~~~~~~
| __delay
arch/hexagon/include/asm/delay.h:11:13: note: '__delay' declared here
11 | extern void __delay(unsigned long cycles);
| ^
2 errors generated.
vim +/rts_delay +438 drivers/tty/serial/xilinx_uartps.c
418
419 /**
420 * cdns_uart_handle_tx - Handle the bytes to be transmitted.
421 * @dev_id: Id of the UART port
422 * Return: None
423 */
424 static void cdns_uart_handle_tx(void *dev_id)
425 {
426 struct uart_port *port = (struct uart_port *)dev_id;
427 struct cdns_uart *cdns_uart = port->private_data;
428 struct tty_port *tport = &port->state->port;
429 unsigned int numbytes;
430 unsigned char ch;
431
432 if (kfifo_is_empty(&tport->xmit_fifo) || uart_tx_stopped(port)) {
433 /* Disable the TX Empty interrupt */
434 writel(CDNS_UART_IXR_TXEMPTY, port->membase + CDNS_UART_IDR);
435 /* Set RTS line after delay */
436 if (cdns_uart->port->rs485.flags & SER_RS485_ENABLED) {
437 cdns_uart->tx_timer.function = &cdns_rs485_rx_callback;
> 438 rts_delay = ns_to_ktime(cdns_calc_after_tx_delay(cdns_uart));
439 hrtimer_start(&cdns_uart->tx_timer, rts_delay, HRTIMER_MODE_REL);
440 }
441 return;
442 }
443
444 numbytes = port->fifosize;
445 while (numbytes &&
446 !(readl(port->membase + CDNS_UART_SR) & CDNS_UART_SR_TXFULL) &&
447 uart_fifo_get(port, &ch)) {
448 writel(ch, port->membase + CDNS_UART_FIFO);
449 numbytes--;
450 }
451
452 if (kfifo_len(&tport->xmit_fifo) < WAKEUP_CHARS)
453 uart_write_wakeup(port);
454
455 /* Enable the TX Empty interrupt */
456 writel(CDNS_UART_IXR_TXEMPTY, cdns_uart->port->membase + CDNS_UART_IER);
457 }
458
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
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