Patchwork spi_mpc8xxx: issue with using definition of pram in Device Tree

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Submitter LEROY Christophe
Date Sept. 16, 2010, 7:05 a.m.
Message ID <20100916070503.10046C7391@messagerie.si.c-s.fr>
Download mbox | patch
Permalink /patch/64942/
State Not Applicable
Delegated to: Grant Likely
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Comments

LEROY Christophe - Sept. 16, 2010, 7:05 a.m.
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>

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Grant Likely - Sept. 24, 2010, 7:10 a.m.
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;
>  }
LEROY Christophe - Sept. 24, 2010, 7:20 a.m.
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;
>>   }
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
Anton Vorontsov - Sept. 24, 2010, 7:57 a.m.
Hello,

On Fri, Sep 24, 2010 at 09:20:27AM +0200, LEROY Christophe wrote:
> 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.

The patch looks OK, I think.

Doesn't explain why that worked on MPC8272 (CPM2) and MPC8560
(also CPM2) machines though. But here's my guess (I no longer
have these boards to test it):

On 8272 I used this node:

+                       spi@4c0 {
+                               #address-cells = <1>;
+                               #size-cells = <0>;
+                               compatible = "fsl,cpm2-spi", "fsl,spi";
+                               reg = <0x11a80 0x40 0x89fc 0x2>;

On that SOC there are two muram data regions 0x0..0x2000 and
0x9000..0x9100. Note that we actually don't want "data" regions,
and the only reason why that worked is that sysdev/cpm_common.c
maps muram(0)..muram(max).

Thanks,
Scott Wood - Sept. 24, 2010, 3:07 p.m.
On Fri, 24 Sep 2010 01:10:06 -0600
Grant Likely <grant.likely@secretlab.ca> wrote:

> 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?

I don't see how cpm_muram_alloc_fixed() can be used safely at all.  If
you need a fixed address, it shouldn't be part of the general
allocation pool, or something else might get it first.

-Scott
Scott Wood - Sept. 24, 2010, 3:12 p.m.
On Fri, 24 Sep 2010 11:57:40 +0400
Anton Vorontsov <cbouatmailru@gmail.com> wrote:

> Doesn't explain why that worked on MPC8272 (CPM2) and MPC8560
> (also CPM2) machines though. But here's my guess (I no longer
> have these boards to test it):
> 
> On 8272 I used this node:
> 
> +                       spi@4c0 {
> +                               #address-cells = <1>;
> +                               #size-cells = <0>;
> +                               compatible = "fsl,cpm2-spi", "fsl,spi";
> +                               reg = <0x11a80 0x40 0x89fc 0x2>;
> 
> On that SOC there are two muram data regions 0x0..0x2000 and
> 0x9000..0x9100. Note that we actually don't want "data" regions,
> and the only reason why that worked is that sysdev/cpm_common.c
> maps muram(0)..muram(max).

Wouldn't it still fail the rh_alloc_fixed call?

-Scott

Patch

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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