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

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Message-ID: <f95ef7b7-cc23-9fed-5d05-1aa66aaeb86a@kernel.org>
Date:   Tue, 22 Nov 2022 08:02:04 +0100
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Michael Walle <michael@...le.cc>
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,

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,
-- 
js