linux-kernel - Re: [PATCH 1/3] tty: serial: 8250: Add new capability for highspeed register

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Date:	Tue, 5 Aug 2014 12:43:43 +0100
From:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
To:	Matthias Brugger <matthias.bgg@...il.com>
Cc:	linux-kernel@...r.kernel.org, robh+dt@...nel.org,
	pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
	rdunlap@...radead.org, gregkh@...uxfoundation.org, jslaby@...e.cz,
	grant.likely@...aro.org, heikki.krogerus@...ux.intel.com,
	alan@...ux.intel.com, paul.gortmaker@...driver.com,
	asierra@...-inc.com, mwelling@...e.org, dianders@...omium.org,
	m-karicheri2@...com, jschultz@...-inc.com, mingo@...e.hu,
	balbi@...com, heiko@...ech.de, devicetree@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-serial@...r.kernel.org,
	linux-api@...r.kernel.org
Subject: Re: [PATCH 1/3] tty: serial: 8250: Add new capability for highspeed
 register

>  
>  	/*
> +	 * Mediatek UARTs use an extra highspeed register (UART_MTK_HIGHS)
> +	 *
> +	 * We need to recalcualte the quot register, as the claculation depends
> +	 * on the vaule in the highspeed register.
> +	 *
> +	 * Some baudrates are not supported by the chip, so we use the next
> +	 * lower rate supported.
> +	 *
> +	 * If highspeed register is set to 3, we need to specify sample count
> +	 * and sample point to increase accuracy. If not, we reset the
> +	 * registers to their default values.
> +	 */

Don't put stuff in the core driver core for your chip specific weirdness,
wrap the termios method with your own in your driver code as a fair
number of other 8250ish drivers do.

If you do that then you don't need to waste a UART CAPS flag and you
don't need to put anything in the core driver code.

Alan
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