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Date: Mon, 22 Apr 2024 08:30:50 +0200
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Subject: Re: [PATCH v5 3/3] serial: sc16is7xx: add support for EXAR XR20M1172
 UART
To: Konstantin Pugin <rilian.la.te@ya.ru>
Cc: krzk@kernel.org, conor@kernel.org, lkp@intel.com, vz@mleia.com,
 robh@kernel.org, jcmvbkbc@gmail.com, nicolas.ferre@microchip.com,
 manikanta.guntupalli@amd.com, corbet@lwn.net, ychuang3@nuvoton.com,
 u.kleine-koenig@pengutronix.de, Maarten.Brock@sttls.nl,
 Konstantin Pugin <ria.freelander@gmail.com>,
 Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
 Jernej Skrabec <jernej.skrabec@gmail.com>,
 Herve Codina <herve.codina@bootlin.com>,
 Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
 Hugo Villeneuve <hvilleneuve@dimonoff.com>,
 Lech Perczak <lech.perczak@camlingroup.com>,
 =?UTF-8?Q?Ilpo_J=C3=A4rvinen?= <ilpo.jarvinen@linux.intel.com>,
 linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org
References: <20240420182223.1153195-1-rilian.la.te@ya.ru>
 <20240420182223.1153195-4-rilian.la.te@ya.ru>
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From: Jiri Slaby <jirislaby@kernel.org>
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In-Reply-To: <20240420182223.1153195-4-rilian.la.te@ya.ru>
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On 20. 04. 24, 20:22, Konstantin Pugin wrote:
> From: Konstantin Pugin <ria.freelander@gmail.com>
> 
> XR20M1172 register set is mostly compatible with SC16IS762, but it has
> a support for additional division rates of UART with special DLD register.
> So, add handling this register by appropriate devicetree bindings.
..
> --- a/drivers/tty/serial/sc16is7xx.c
> +++ b/drivers/tty/serial/sc16is7xx.c
..
> @@ -555,18 +578,43 @@ static bool sc16is7xx_regmap_noinc(struct device *dev, unsigned int reg)
>   	return reg == SC16IS7XX_RHR_REG;
>   }
>   
> +static bool sc16is7xx_has_dld(struct device *dev)
> +{
> +		struct sc16is7xx_port *s = dev_get_drvdata(dev);
> +
> +		if (s->devtype == &xr20m1172_devtype)
> +			return true;
> +		return false;

:) so this should simply be:

return s->devtype == &xr20m1172_devtype;

..
> @@ -1002,6 +1052,7 @@ static void sc16is7xx_set_termios(struct uart_port *port,
>   				  const struct ktermios *old)
>   {
>   	struct sc16is7xx_one *one = to_sc16is7xx_one(port, port);
> +	bool has_dld = sc16is7xx_has_dld(port->dev);
>   	unsigned int lcr, flow = 0;
>   	int baud;
>   	unsigned long flags;
> @@ -1084,7 +1135,7 @@ static void sc16is7xx_set_termios(struct uart_port *port,
>   	/* Get baud rate generator configuration */
>   	baud = uart_get_baud_rate(port, termios, old,
>   				  port->uartclk / 16 / 4 / 0xffff,
> -				  port->uartclk / 16);
> +				  port->uartclk / (has_dld ? 4 : 16));

Could you do this instead:
unsigned int divisor = sc16is7xx_has_dld(port->dev) ? 4 : 16;

..

uart_get_baud_rate(..., port->uartclk / divisor);


I am not sure the above warrants for a new version. Just in case you are 
sending one.

thanks,
-- 
js
suse labs