linux-mips
[Top] [All Lists]

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

To: Shmulik Ladkani <jungoshmulik@gmail.com>
Subject: Re: serial port 8250 messed up after coverting from little endian to big endian on kernel 2.6.31
From: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Date: Wed, 28 Oct 2009 14:04:00 +0300
Cc: myuboot@fastmail.fm, Florian Fainelli <florian@openwrt.org>, linux-kernel@vger.kernel.org, linux-mips <linux-mips@linux-mips.org>, shmulik@jungo.com
In-reply-to: <20091028103551.0b4052d8@pixies.home.jungo.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <1255735395.30097.1340523469@webmail.messagingengine.com> <4AD906D8.3020404@caviumnetworks.com> <1255996564.10560.1340920621@webmail.messagingengine.com> <200910200817.24018.florian@openwrt.org> <1256676013.24305.1342273367@webmail.messagingengine.com> <20091028103551.0b4052d8@pixies.home.jungo.com>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Thunderbird 2.0.0.23 (Windows/20090812)
Hello.

Shmulik Ladkani wrote:

Thanks, Florian. I found the cause of the problem. My board is 32 bit
based, so each serial port register is 32bit even only 8 bit is used. So
when the board is switched endianess, I need to change the address
offset to access the same registers.
For example, original RHR register address is 0x8001000 with little
endian mode. With big endian, I need to access it as 0x8001003.

I assume your uart_port's iotype is defined as UPIO_MEM32.

  He wouldn't have to add 3 to the register addresses then.

UPIO_MEM32 makes 8250 access serial registers using readl/writel (which might
be a problem for big-endian), while UPIO_MEM makes 8250 access the registers
using readb/writeb.

  Both may be a problem for big endian.

Maybe you should try UPIO_MEM (assuming hardware allows byte access).

  Contrarywise, I think he now has UPIO_MEM and needs to try UPIO_MEM32.

WBR, Sergei



<Prev in Thread] Current Thread [Next in Thread>