linux-kernel - Re: [PATCH] ARM: tegra: dts: add aliases and DMA requestor for serial controller

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Message-ID: <50D344E9.70305@wwwdotorg.org>
Date:	Thu, 20 Dec 2012 10:03:37 -0700
From:	Stephen Warren <swarren@...dotorg.org>
To:	Laxman Dewangan <ldewangan@...dia.com>
CC:	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARM: tegra: dts: add aliases and DMA requestor for serial
 controller

On 12/19/2012 11:15 PM, Laxman Dewangan wrote:
> On Wednesday 19 December 2012 10:30 PM, Stephen Warren wrote:
>> On 12/18/2012 11:31 PM, Laxman Dewangan wrote:
>>> Add APB DMA requestor and serial aliases for serial controller.
>>> There will be two serial driver i.e. 8250 based simple serial driver
>>> and APB DMA based serial driver for higher baudrate and performace.
>>>
>>> The simple serial driver get enabled with compatible nvidia,tegra20-uart
>>> and APB DMA based driver will get enabled with compatible
>>> nvidia,tegra20-hsuart.
>> This patch seems to do two things:
>>
>> 1) Add a comment describing how to select the basic or DMA-based driver.
>> I can see why this is useful.
>>
>> 2) Add aliases for the serial ports. I have no idea why this is useful.
> 
> Serial aliases are added because we want to get the port number like
> /dev/ttyTHS0,  /d/ttyTHS2 etc. The uarta should be /dev/ttyTHS0 and
> uartc should be /dev/ttyTHS2. The port number can be found using aliases
> and of_alias_get_id() in driver file:
> 
> port_number = of_alias_get_id(np, "serial");

Oh, I see. I guess the aliases make sense then.

But, wouldn't you only add aliases for the specific UARTs that are in
use on a particular board (so put them in tegraNN-board.dts) rather than
all UARTs on Tegra (i.e. the current patch which puts them into
tegraNN.dtsi)?
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