linux-kernel - Re: [PATCH v2 1/3] serial: 8250: Handle UART without interrupt on TEMT using em485

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Date:   Fri, 1 Oct 2021 14:48:42 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Eric Tremblay <etremblay@...tech-controls.com>
Cc:     gregkh@...uxfoundation.org, jslaby@...e.com,
        matwey.kornilov@...il.com, giulio.benetti@...ronovasrl.com,
        lukas@...ner.de, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        christoph.muellner@...obroma-systems.com, heiko@...ech.de,
        heiko.stuebner@...obroma-systems.com
Subject: Re: [PATCH v2 1/3] serial: 8250: Handle UART without interrupt on
 TEMT using em485

On Thu, Feb 04, 2021 at 11:11:56AM -0500, Eric Tremblay wrote:
> The patch introduce the UART_CAP_NOTEMT capability. The capability

s/The patch//

> indicate that the UART doesn't have an interrupt available on TEMT.

indicates

> In the case where the device does not support it, we calculate the
> maximum time it could take for the transmitter to empty the
> shift register. When we get in the situation where we get the
> THRE interrupt, we check if the TEMT bit is set. If it's not, we start
> the a timer and recall __stop_tx() after the delay.
> 
> The transmit sequence is a bit modified when the capability is set. The
> new timer is used between the last interrupt(THRE) and a potential
> stop_tx timer.

> Signed-off-by: Giulio Benetti <giulio.benetti@...ronovasrl.com>
> [moved to use added UART_CAP_TEMT]
> Signed-off-by: Heiko Stuebner <heiko.stuebner@...obroma-systems.com>
> [moved to use added UART_CAP_NOTEMT, improve timeout]
> Signed-off-by: Eric Tremblay <etremblay@...tech-controls.com>

Does it need Co-developed-by tag(s)?

...

> +#define UART_CAP_NOTEMT	(1 << 18)	/* UART without interrupt on TEMT available*/

Missed space in the comment .

...

> +static inline void serial8250_em485_update_temt_delay(struct uart_8250_port *p,
> +			unsigned int cflag, unsigned int baud)
> +{
> +	unsigned int bits;
> +
> +	if (!p->em485)
> +		return;
> +
> +	bits = uart_get_byte_size(cflag);

Should be rebased. We have tty_get_frame_size() for a while.

> +	p->em485->no_temt_delay = bits * NSEC_PER_SEC / baud;
> +}

-- 
With Best Regards,
Andy Shevchenko