linux-kernel - Re: [PATCH v3 3/3] serial: sc16is7xx: add support for EXAR XR20M1172 UART

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Date: Fri, 19 Apr 2024 08:42:13 +0200
From: Jiri Slaby <jirislaby@...nel.org>
To: Konstantin Pugin <rilian.la.te@...ru>
Cc: Konstantin Pugin <ria.freelander@...il.com>,
 Vladimir Zapolskiy <vz@...ia.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Hugo Villeneuve <hvilleneuve@...onoff.com>,
 Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 Lech Perczak <lech.perczak@...lingroup.com>,
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
 Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
 linux-serial@...r.kernel.org
Subject: Re: [PATCH v3 3/3] serial: sc16is7xx: add support for EXAR XR20M1172
 UART

On 18. 04. 24, 19:06, Konstantin Pugin wrote:
> From: Konstantin Pugin <ria.freelander@...il.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.
> 
> Reviewed-by: Vladimir Zapolskiy <vz@...ia.com>
> Signed-off-by: Konstantin Pugin <ria.freelander@...il.com>
> ---
>   drivers/tty/serial/sc16is7xx.c | 55 +++++++++++++++++++++++++++++++---
>   1 file changed, 51 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
> index a300eebf1401..59376c637467 100644
> --- a/drivers/tty/serial/sc16is7xx.c
> +++ b/drivers/tty/serial/sc16is7xx.c
..
> @@ -556,16 +579,33 @@ static bool sc16is7xx_regmap_noinc(struct device *dev, unsigned int reg)
>   
>   static int sc16is7xx_set_baud(struct uart_port *port, int baud)
>   {
> +	struct sc16is7xx_port *s = dev_get_drvdata(port->dev);
>   	struct sc16is7xx_one *one = to_sc16is7xx_one(port, port);
> -	u8 lcr;
> +	unsigned long clk = port->uartclk, div, div16;
> +	bool has_dld = s->devtype->has_dld;
> +	u8 dld_mode = XR20M117X_DLD_16X;
>   	u8 prescaler = 0;
> -	unsigned long clk = port->uartclk, div = clk / 16 / baud;
> +	u8 divisor = 16;
> +	u8 lcr;
> +
> +	if (has_dld && DIV_ROUND_CLOSEST(clk, baud) < 16)
> +		divisor = 1 << (fls(DIV_ROUND_CLOSEST(clk, baud)) - 1);

Do you mimic roundup_pow_of_two()?

-- 
js
suse labs