linux-kernel - Re: [PATCH4/4] [POWERPC] Fix cpm

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Date:	Mon, 24 Sep 2007 13:22:01 -0500
From:	Scott Wood <scottwood@...escale.com>
To:	Jochen Friedrich <jochen@...am.de>
CC:	linuxppc-embedded@...abs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH4/4] [POWERPC] Fix cpm_uart driver

Jochen Friedrich wrote:
> Scott Wood schrieb:
>> Jochen Friedrich wrote:
>>>
>>> In cpm_uart_core, functions cpm_uart_init_bd and cpm_uart_init_scc
>>> an offset into DP RAM is calculated by substracting a physical
>>> memory constant from an virtual address. This patch fixes the
>>> problem by converting the virtual address into a physical
>>> first.
>>
>> Huh?  DPRAM_BASE is a virtual address.  With this patch, you'd be 
>> subtracting a virtual address from a physical address.
> 
> Thanks for pointing me to it. So the bug is in cpm_uart_cpm1.h assigning 
> a physical memory to DPRAM_BASE (at least on ARC=ppc). cpm_uart_cpm2.h 
> seems to be correct though. I'll submit a new patch for this.

cpmp is a physical address on arch/ppc?
/me looks at arch/ppc/8xx_io/commproc.c

Yikes.  Please don't change cpm_uart_cpm1.h, as it's correct for 
arch/powerpc, and there are numerous other places that assume cpmp is 
virtual (including in the very same function that assigns it a physical 
address).

You could fix arch/ppc if you want, though it may be easier to wait for 
it to die, and insist on identity maps in the meantime. :-)

-Scott
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