On Wednesday 19 December 2012 10:30 PM, Stephen Warren wrote:

On 12/18/2012 11:31 PM, Laxman Dewangan wrote:

quoted

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");