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Re: serial port 8250 messed up after coverting from little endian to big

Subject: Re: serial port 8250 messed up after coverting from little endian to big endian on kernel 2.6.31
From: Shmulik Ladkani <>
Date: Thu, 29 Oct 2009 10:26:52 +0200
Cc: "Sergei Shtylyov" <>, "Florian Fainelli" <>,, "linux-mips" <>,
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On Wed, 28 Oct 2009 14:36:15 -0500 wrote:
> I just tried UPIO_MEM32 without adding a offset of 3. But the result is
> bad - after the kernel initializes the serial console, the console print
> out messes up. The early printk is fine because the u-boot initialises
> the serial port fine. 
> Did I miss anything? Thanks again for your help.

I guess you did fine with UPIO_MEM32.

Keeping the UPIO_MEM32 approach, I suggest also to fiddle Y/N with
CONFIG_SWAP_IO_SPACE (might be that you have it set to Y while you don't
really need it, or vice versa).
This is since 'readl' uses 'ioswabl' for (potential) byte-swapping of the read
value. Take a look at asm/io.h and mangle-port.h.

Most important, read your hardware documentation to determine correct access
to the memory mapped serial registers.

Shmulik Ladkani         Jungo Ltd.

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