Messages in this thread | | | Date | Tue, 22 Nov 2022 10:13:52 +0100 | From | Michael Walle <> | Subject | Re: [PATCH v5 2/3] tty: serial: use uart_port_tx() helper |
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Am 2022-11-22 09:25, schrieb Jiri Slaby: > On 22. 11. 22, 9:23, Jiri Slaby wrote: >> On 22. 11. 22, 9:18, Michael Walle wrote: >>> Am 2022-11-22 09:09, schrieb Michael Walle: >>>> Hi, >>>> >>>> Am 2022-11-22 08:02, schrieb Jiri Slaby: >>>>> On 21. 11. 22, 21:27, Michael Walle wrote: >>>>>> This will break serial output for the userspace on my board >>>>>> (arch/arm/boot/dts/lan966x-kontron-kswitch-d10-mmt*dts). The >>>>>> uart_port_tx() >>>>>> helper will call __port->ops->stop_tx(__port) if >>>>>> uart_circ_chars_pending() >>>>>> returns 0. But the code above, doesn't do that. In fact, removing >>>>>> the >>>>>> stop_tx() call in the helper macro, will fix the console output. >>>>>> >>>>>> Any ideas how to fix that? >>>>> >>>>> Hm, so ATMEL_US_TXRDY is removed from tx_done_mask in stop_tx, but >>>>> not >>>>> added back in start_tx. So the tx interrupt is never handled (the >>>>> tx >>>>> tasklet is not scheduled to send the queue chars) in >>>>> atmel_handle_transmit(). >>>>> >>>>> Any chance, the below fixes it? >>>>> >>>>> diff --git a/drivers/tty/serial/atmel_serial.c >>>>> b/drivers/tty/serial/atmel_serial.c >>>>> index 11bf2466390e..395370e0c77b 100644 >>>>> --- a/drivers/tty/serial/atmel_serial.c >>>>> +++ b/drivers/tty/serial/atmel_serial.c >>>>> @@ -596,6 +596,8 @@ static void atmel_start_tx(struct uart_port >>>>> *port) >>>>> /* re-enable PDC transmit */ >>>>> atmel_uart_writel(port, ATMEL_PDC_PTCR, >>>>> ATMEL_PDC_TXTEN); >>>>> >>>>> + atmel_port->tx_done_mask |= ATMEL_US_TXRDY; >>>>> + >>>>> /* Enable interrupts */ >>>>> atmel_uart_writel(port, ATMEL_US_IER, >>>>> atmel_port->tx_done_mask); >>>>> >>>>> >>>>> thanks, >>>> >>>> Unfortunately, that doesn't help. Btw, some characters are >>>> transmitted: >>>> >>>> >>>> [ 6.219356] Key type dns_resolver registered >>>> [ 6.223679] Registering SWP/SWPB emulation handler >>>> [ 6.247530] Loading compiled-in X.509 certificates >>>> [ 6.288467] Freeing unused kernel image (initmem) memory: 1024K >>>> [ 6.297789] Run /init as init process >>>> WbSOROSOSOSOSOStarting linuxptp system clock synchronization: O >>>> >>>> -michael >>> >>> But you made me look at atmel_stop_tx() and there is this: >>> >>> /* >>> * Disable the transmitter. >>> * This is mandatory when DMA is used, otherwise the DMA buffer >>> * is fully transmitted. >>> */ >>> atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXDIS); >>> >>> Removing that write, will also fix the problem. Could it be, that >>> the transmit is still active (via DMA) but the driver will call >>> tx_stop() and then stop the transmission in the background? >> >> Yes, that was exactly the next step to try. The datasheet doesn't tell >> much what happens when TXDIS is written while the characters are >> transmitted. > > Side note: your usart doesn't use dma. It's PIO (hence all that > uart_tx_helper()). And the attached patch doesn't touch TXDIS for > non-DMA case. I.e. it should transmit the final character (and nothing > more).
ok ;)
expect from "s/id_dma/is_dma/", this patch works. thanks!
-michael
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