Cortex-A9 SCU + ARM_ERRATA_764369

[Mason]

On 03/11/2015 21:36, Mason wrote:

> On 03/11/2015 20:52, Mason wrote:
> 
>> Mark Rutland wrote:
>>
>>> Mason wrote:
>>>
>>>> What is scu_base + 0x30? (SCU diagnostic control register?)
>>>
>>> It's documented (admittedly very sparsely) in the Software
>>> Developers Errata Notice for Cortex-A9 processors, in the
>>> section regarding erratum 764369.
>>
>> A Freescale document mentions:
>>
>>> Set bit[0] in the undocumented SCU diagnostic control register
>>> located at offset 0x30 from the PERIPHBASE address. Setting this bit
>>> disables the "migratory bit" feature. This forces a dirty cache line
>>> to be evicted to the lower memory subsystem—which is both the point
>>> of coherency and the point of unification—when it is being read by
>>> another processor.
>>
>> Can this register be written to by a non-secure OS?
> 
> IIUC Rob's message, NS OS cannot write to scu_base + 0x30.
> http://lists.infradead.org/pipermail/linux-arm-kernel/2014-April/244341.html
> 
> <confused> Rob stated:
> "these types of work-arounds must go into the bootloader or firmware."
> 
> Doesn't that apply to 764369 too? (At least the part setting
> bit0 in scu_base + 0x30)
> 
> If a company is not using a standard boot-loader such as U-Boot,
> does that mean it must re-implement all these work-arounds in
> its own boot-loader?

AFAICT, U-Boot implements the following work-arounds.
http://git.denx.de/?p=u-boot.git;a=blob;f=README

	CONFIG_ARM_ERRATA_716044
	CONFIG_ARM_ERRATA_742230
	CONFIG_ARM_ERRATA_743622
	CONFIG_ARM_ERRATA_751472
	CONFIG_ARM_ERRATA_761320
	CONFIG_ARM_ERRATA_773022
	CONFIG_ARM_ERRATA_774769
	CONFIG_ARM_ERRATA_794072

I'll have to talk to the boot-loader and secure OS devs.

Regards.