linux-kernel - Re: [PATCH v5 2/3] tty: serial: use uart_port

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Message-ID: <0ef4f1e6d92601a39fe0d1c316506c12@walle.cc>
Date:   Tue, 22 Nov 2022 09:09:36 +0100
From:   Michael Walle <michael@...le.cc>
To:     Jiri Slaby <jirislaby@...nel.org>
Cc:     afaerber@...e.de, alexandre.belloni@...tlin.com,
        claudiu.beznea@...rochip.com, festevam@...il.com,
        gregkh@...uxfoundation.org, ilpo.jarvinen@...ux.intel.com,
        kernel@...gutronix.de, linux-imx@....com,
        linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
        liviu.dudau@....com, lorenzo.pieralisi@....com, mani@...nel.org,
        nicolas.ferre@...rochip.com, richard.genoud@...il.com,
        s.hauer@...gutronix.de, shawnguo@...nel.org, sudeep.holla@....com,
        tklauser@...tanz.ch, vz@...ia.com
Subject: Re: [PATCH v5 2/3] tty: serial: use uart_port_tx() helper

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