linux-kernel - Re: [PATCH v1 tty] 8250: microchip: Add 4 Mbps support in PCI1XXXX UART

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Date: Sun, 28 Jan 2024 17:27:23 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Rengarajan S <rengarajan.s@...rochip.com>
Cc: kumaravel.thiagarajan@...rochip.com,
	tharunkumar.pasumarthi@...rochip.com, gregkh@...uxfoundation.org,
	jirislaby@...nel.org, ilpo.jarvinen@...ux.intel.com,
	f.fainelli@...il.com, john.ogness@...utronix.de, tony@...mide.com,
	tglx@...utronix.de, jiaqing.zhao@...ux.intel.com,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
	UNGLinuxDriver@...rochip.com
Subject: Re: [PATCH v1 tty] 8250: microchip: Add 4 Mbps support in PCI1XXXX
 UART

On Thu, Jan 25, 2024 at 03:36:19PM +0530, Rengarajan S wrote:
> The current clock input is set to 62.5 MHz for supporting fractional
> divider, which enables generation of an acceptable baud rate from any
> frequency. With the current clock input the baud rate range is limited
> to 3.9 Mbps. Hence, the current range is extended to support 4 Mbps
> with Burst mode operation. Divisor calculation for a given baud rate is
> updated as the sampling rate is reduced from 16 to 8 for 4 Mbps.

..

> +#define UART_BAUD_4MBPS				4000000

(4 * MEGA) ? (will need to include units.h, if not yet)

..

> +	frac_div = readl(port->membase + FRAC_DIV_CFG_REG);

> +

Unneeded blank line.

> +	if (frac_div == UART_BIT_DIVISOR_16)
> +		sample_cnt = UART_BIT_SAMPLE_CNT_16;
> +	else
> +		sample_cnt = UART_BIT_SAMPLE_CNT_8;

..

> +	/*
> +	 * Microchip PCI1XXXX UART supports maximum baud rate up to 4 Mbps
> +	 */
> +	if (up->port.type == PORT_MCHP16550A)
> +		max = 4000000;

No. Please refactor the way the 8250_port won't be modified.

Also you have a define for this constant, use it.

-- 
With Best Regards,
Andy Shevchenko