lkml.org 
[lkml]   [2022]   [Nov]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v5 2/3] tty: serial: use uart_port_tx() helper
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


\
 
 \ /
  Last update: 2022-11-22 10:15    [W:0.039 / U:0.216 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site