[U-Boot] Exynos 5800/5422 CPU ID inconsistency.

[U-Boot] Exynos 5800/5422 CPU ID inconsistency.

[Przemyslaw Marczak]

Hello,

The s5p_cpu_id variable is set in here:
arch/arm/mach-exynos/include/mach/cpu.h

For value 0x422, found in pro id register, the s5p_cpu_id is set as 
0x5800. I think, that hiding the real info is wrong and misleading.

I don't have documentation for E5800, but maybe there is some additional 
register like package id to recognise the SoC variant.

I'm pointing this issue, because for older boards, we used this 
information to set the $fdtfile environment variable name, to next load 
proper fdt from partition before boot the kernel.

Now, I would like use the s5p_cpu_id to set the fdtfile name for Odroid 
XU3/4, but the value is bad.

I would like fix this value to the real one, but then, the CPU name will 
change on Chromebooks.

To fix this we could add "cpu-name" property to device tree, and then 
print it.

What do you think about this?

Best regards,
-- 
Przemyslaw Marczak
Samsung R&D Institute Poland
Samsung Electronics
p.marczak at samsung.com

[U-Boot] Exynos 5800/5422 CPU ID inconsistency.

[Simon Glass]

Hi Przemyslaw,

On 26 August 2015 at 06:09, Przemyslaw Marczak <p.marczak@samsung.com> wrote:
> Hello,
>
> The s5p_cpu_id variable is set in here:
> arch/arm/mach-exynos/include/mach/cpu.h
>
> For value 0x422, found in pro id register, the s5p_cpu_id is set as 0x5800.
> I think, that hiding the real info is wrong and misleading.
>
> I don't have documentation for E5800, but maybe there is some additional
> register like package id to recognise the SoC variant.
>
> I'm pointing this issue, because for older boards, we used this information
> to set the $fdtfile environment variable name, to next load proper fdt from
> partition before boot the kernel.
>
> Now, I would like use the s5p_cpu_id to set the fdtfile name for Odroid
> XU3/4, but the value is bad.
>
> I would like fix this value to the real one, but then, the CPU name will
> change on Chromebooks.
>
> To fix this we could add "cpu-name" property to device tree, and then print
> it.
>
> What do you think about this?

That seems fine to me.

Regards,
Simon

[U-Boot] Exynos 5800/5422 CPU ID inconsistency.

[Sjoerd Simons]

On Wed, 2015-08-26 at 06:37 -0700, Simon Glass wrote:
> Hi Przemyslaw,
> 
> On 26 August 2015 at 06:09, Przemyslaw Marczak <p.marczak@samsung.com
> > wrote:
> > Hello,
> > 
> > The s5p_cpu_id variable is set in here:
> > arch/arm/mach-exynos/include/mach/cpu.h
> > 
> > For value 0x422, found in pro id register, the s5p_cpu_id is set as 
> > 0x5800.
> > I think, that hiding the real info is wrong and misleading.
> > 
> > I don't have documentation for E5800, but maybe there is some 
> > additional
> > register like package id to recognise the SoC variant.
> > 
> > I'm pointing this issue, because for older boards, we used this 
> > information
> > to set the $fdtfile environment variable name, to next load proper 
> > fdt from
> > partition before boot the kernel.
> > 
> > Now, I would like use the s5p_cpu_id to set the fdtfile name for 
> > Odroid
> > XU3/4, but the value is bad.
> > 
> > I would like fix this value to the real one, but then, the CPU name 
> > will
> > change on Chromebooks.
> > 
> > To fix this we could add "cpu-name" property to device tree, and 
> > then print
> > it.

I was wondering recently whether there shouldn't simply be a device
-tree property with the name of the fdt file as used by linux such
there is no need for putting this dynamically together which can be a
tad error-prone (as this example shows). (Unfortunately not all boards
in linux use the <cpu name>-<board name> convention :/) 


-- 
Sjoerd Simons
Collabora Ltd.

[U-Boot] Exynos 5800/5422 CPU ID inconsistency.

[Przemyslaw Marczak]

Hello Sjoerd,

On 08/26/2015 10:56 PM, Sjoerd Simons wrote:
> On Wed, 2015-08-26 at 06:37 -0700, Simon Glass wrote:
>> Hi Przemyslaw,
>>
>> On 26 August 2015 at 06:09, Przemyslaw Marczak <p.marczak@samsung.com
>>> wrote:
>>> Hello,
>>>
>>> The s5p_cpu_id variable is set in here:
>>> arch/arm/mach-exynos/include/mach/cpu.h
>>>
>>> For value 0x422, found in pro id register, the s5p_cpu_id is set as
>>> 0x5800.
>>> I think, that hiding the real info is wrong and misleading.
>>>
>>> I don't have documentation for E5800, but maybe there is some
>>> additional
>>> register like package id to recognise the SoC variant.
>>>
>>> I'm pointing this issue, because for older boards, we used this
>>> information
>>> to set the $fdtfile environment variable name, to next load proper
>>> fdt from
>>> partition before boot the kernel.
>>>
>>> Now, I would like use the s5p_cpu_id to set the fdtfile name for
>>> Odroid
>>> XU3/4, but the value is bad.
>>>
>>> I would like fix this value to the real one, but then, the CPU name
>>> will
>>> change on Chromebooks.
>>>
>>> To fix this we could add "cpu-name" property to device tree, and
>>> then print
>>> it.
>
> I was wondering recently whether there shouldn't simply be a device
> -tree property with the name of the fdt file as used by linux such
> there is no need for putting this dynamically together which can be a
> tad error-prone (as this example shows). (Unfortunately not all boards
> in linux use the <cpu name>-<board name> convention :/)
>
>

This could be good for the boards with only one kernel compatible fdt file.

But for Exynos, there can be more than one kernel compatible fdt for a 
single U-Boot binary like for Odroid XU3/3L/4 or Odroid U3/X2.
There are also other platforms with this issue, like imx6 wandboard.

Adding common feature for board detection, may be complicated.

After some quick research, I think that adding "cpu-name" to fdt will 
look not pretty. Change the name of "cpus" node to the SoC name would be 
nice, but will break the compatibility with the kernel and U-Boot's 
UCLASS_CPU driver.

In this case, adding a line:

#define CONFIG_CPU_NAME  "Exynos5800"

only to the peach-pi.h seem to be reasonable, because for other Exynos 
platforms the CPU name is proper.

Best regards,
-- 
Przemyslaw Marczak
Samsung R&D Institute Poland
Samsung Electronics
p.marczak at samsung.com