Re: serial console: platform_device

[Sergei Shtylyov <sshtylyov@ru.mvista.com>]

Hello.

Ashlesha Shintre wrote:

>>>3) control goes into the serial8250_probe function and assigns values
>>>from the plat_serial8250_port encm3_via_uart_data to the port..so what
>>>is the basic difference between registration of "probe device" versus

>>>"platform bus" devices in the 2.6 kernel?

>>    I'm not sure I follow you here.

> What I meant was, what was the basis for the implementation of
> platform_device and platform_init functions in 2.6?

    This is a convenient way to registers the various SoC and on-board devices 
residing on the busses that can't be scanned like ISA/LPC/whatever (and unlike 
PCI, for example).

> By my understanding the way it worked in 2.4 was by the device probing
> functions that would allocate memory, io ports etc..

    Basically, you don't need to probe for device which you *know* is there, 
you just need to tell the driver where it is.

> m working on making the changes you suggested --

> without the addition of the platform_device and other structures, the

    I meant that you *only* need struct plat_serial8250_port, and not 
platform_device.

> serial console is never detected -- I never get a msg at boot time that
> reads 

> serial8250: ttyS0 at I/O 0x3f8 (irq = whatever) is a 16550A

> so I think i might need these routines

> Also, the Southbridge interrupts are assigned interrupt number:
> AU1000_GPIO_0..and I have included this as below:

    Ah, I forgot to mention that if your UART is a part of the south bridge, 
its IRQ number is _4_ on the integrated 8259 interrupt controller. I'm sure 
that AU1000_GPIO_0 is the cascaded interrupt request from 8259, not the UART's 
own IRQ...

>>static struct plat_serial8250_port encm3_via_uart_data[] = {
>>                {
>>                        .mapbase        = 0x3f8,
>>                        .irq            = AU1000_GPIO_0,

    So, this is wrong. You need to specify to what platform IRQ 8259's IRQ4 
gets routed here.

> Thanks again!
> Ashlesha.

WBR, Sergei