Re: [PATCH] spi_mpc8xxx: issue with using definition of pram in Device Tree

[LEROY Christophe <christophe.leroy@c-s.fr>]

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  Hello,

The issue is that cpm_muram_alloc_fixed() allocates memory from the 
general purpose muram area (from 0x0 to 0x1bff).
Here we need to return a pointer to the parameter RAM, which is located 
somewhere starting at 0x1c00. It is not a dynamic allocation that is 
required here but only to point on the correct location in the parameter 
RAM.

For the CPM2, I don't know. I'm working with a MPC866.

Attached is a previous discussion on the subject where I explain a bit 
more in details the issue.

Regards
C. Leroy

Le 24/09/2010 09:10, Grant Likely a écrit :
> On Thu, Sep 16, 2010 at 09:05:03AM +0200, christophe leroy wrote:
>> This patch applies to 2.6.34.7 and 2.6.35.4
>> It fixes an issue during the probe for CPM1 with definition of parameter ram from DTS
>>
>> Signed-off-by: christophe leroy<christophe.leroy@c-s.fr>
> I'm sorry, I don't understand the fix from the given description.
> What is the problem, and why is cpm_muram_alloc_fixed() the wrong
> thing to call on CPM1?  Does CPM2 still need it?
>
> g.
>
>> diff -urN b/drivers/spi/spi_mpc8xxx.c c/drivers/spi/spi_mpc8xxx.c
>> --- b/drivers/spi/spi_mpc8xxx.c	2010-09-08 16:43:50.000000000 +0200
>> +++ c/drivers/spi/spi_mpc8xxx.c	2010-09-08 16:44:03.000000000 +0200
>> @@ -822,7 +822,7 @@
>>   	if (!iprop || size != sizeof(*iprop) * 4)
>>   		return -ENOMEM;
>>
>> -	spi_base_ofs = cpm_muram_alloc_fixed(iprop[2], 2);
>> +	spi_base_ofs = iprop[2];
>>   	if (IS_ERR_VALUE(spi_base_ofs))
>>   		return -ENOMEM;
>>
>> @@ -844,7 +844,6 @@
>>   			return spi_base_ofs;
>>   	}
>>
>> -	cpm_muram_free(spi_base_ofs);
>>   	return pram_ofs;
>>   }

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From: Scott Wood <scottwood@freescale.com>
To: LEROY Christophe <christophe.leroy@c-s.fr>
Cc: Kumar Gala <kumar.gala@freescale.com>, LinuxPPC-dev <linuxppc-dev@lists.ozlabs.org>
Subject: Re: Small issue at init with spi_mpc8xxx.c with CPM1
Date: Tue, 7 Sep 2010 15:00:38 -0500
Message-ID: <20100907150038.57a7b065@schlenkerla.am.freescale.net>

On Tue, 7 Sep 2010 11:17:17 +0200
LEROY Christophe <christophe.leroy@c-s.fr> wrote:

> 
>   Dear Kumar,
> 
> I have a small issue in the init of spi_mpc8xxx.c with MPC866 (CPM1)
> 
> Unlike cpm_uart that maps the parameter ram directly using 
> of_iomap(np,1), spi_mpc8xxx.c uses cpm_muram_alloc_fixed().
> 
> This has two impacts in the .dts file:
> * The driver must be declared with pram at 1d80 instead of 3d80 whereas 
> it is not a child of muram@2000 but a child of cpm@9c0
> * muram@2000/data@0 must be declared with reg = <0x0 0x2000>   whereas 
> is should be reg=<0x0 0x1c00> to avoid cpm_muram_alloc() to allocate 
> space from parameters ram.
> 
> Maybe I misunderstood something ?

Don't make the device tree lie, fix the driver instead.

The allocator should not be given any chunks of muram that are
dedicated to a fixed purpose -- it might hand it out to something else
before you reserve it.  I don't think that cpm_muram_alloc_fixed() has
any legitimate use at all.

-Scott

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