linux-kernel - Re: 8250 UART doesn't work

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Date:	Sat, 8 Dec 2012 17:01:54 +0000 (UTC)
From:	Woody Wu <narkewoody@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: Re: 8250 UART doesn't work

On 2012-12-07, Alan Cox <alan@...rguk.ukuu.org.uk> wrote:
>> The UART controller is EXAR ST16C554D.  It claims as a 16550
>> compatible controller. Each ST16C554D module contains 4 UART, each of
>> them can be selected via two chip select pad. I think the board
>> hardware, via a CPLD, make the chip selection transparent to the CPU, so
>> by a 5-bit address, CPU can addressing individual 8 16550 compatible
>> registers of each UART.
>
> The EXAR should work. Make sure you have all the addressing and setup
> right would be my first suggestion - then poke at the registers by hand
> and double check.
>
> Alan

Do you think my iotype (UPIO_MEM) and flags ((UPF_BOOT_AUTOCONF |
UPF_IOREMAP | UPF_SHARE_IRQ)) settings are normal in a ARM board?

In the same directory with the 8250.c driver source, I foudn a 16C554
ports definition file 8250_exar_st16c554.c, in which the UART
definitions are quite different with that in my case:

#define PORT(_base,_irq)				\
	{						\
		.iobase		= _base,		\
		.irq		= _irq,			\
		.uartclk	= 1843200,		\
		.iotype		= UPIO_PORT,		\
		.flags		= UPF_BOOT_AUTOCONF,	\
	}

static struct plat_serial8250_port exar_data[] = {
	PORT(0x100, 5),
	PORT(0x108, 5),
	PORT(0x110, 5),
	PORT(0x118, 5),
	{ },
};

You see this file use UPIO_PORT as iotype and provide not mapbase but
iobase.

Which kind of configuration is right for ARM?  I think the
8250_exar_st16c554.c is for ISA bus board and hence is not suit to me,
but I am not sure my understanding is right. Please give me some
backgroud information on this field.

Thanks.


-- 
woody
I can't go back to yesterday - because I was a different person then.

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