[U-Boot] [RFC] ARM: omap3: Add option to disable errata workarounds.

[Andreas Bießmann]

Hi Andreas,

On 07/09/2013 05:01 PM, Andreas Naumann wrote:
>>>> It seems that all three ARM errata workarounds done in omap3 board-init
>>>> (#454179 #430973 #621766) are solved/not longer needed e.g. in the
>>>> AM/DM37xx chips. Other people have noticed this:
>>>> http://e2e.ti.com/support/arm/sitara_arm/f/791/t/254742.aspx
>>>>
>>>> When still applying them (especcially #430973), lots of segmentations
>>>> faults and other strange stuff begin to appear.
>>
>> I read your link the other way round. If the #430973 errata fix is _not_
>> applied to r3p2 it gives a lot of segfaults. Unfortunately the thread
>> has noc more information on that.
> 
> I dont know what bootloader the guy used, but he states that he needs to
> enable the errata fix in the kernel for the segfaults to disappear. I
> found exactly the same: Initially I had no errata fixes configured for
> the kernel, only when I added them the segfaults disappeared.
> However they also disappear if I remove the workarounds from kernel as
> well as u-boot, hence this patch.

Ok, understand.

<snip>

>> I join Albert's suggestion. Another solution could be to read the
>> silicon revision and enable erratum workarounds on that information. It
>> would be a step towards single binary.
> 
> So I'd rather do that, but can we map the ARM revision e.g. r2p1 to the
> TI die versions ES1.0, 1.1 and so on? Or can the ARM revision be read
> directly?

You should use the ARM revisions. They are available, but dunno how:

---8<---
~ cat /proc/cpuinfo
Processor	: ARMv7 Processor rev 2 (v7l)
BogoMIPS	: 512.57
Features	: swp half thumb fastmult vfp edsp thumbee neon vfpv3 tls
CPU implementer	: 0x41
CPU architecture: 7
CPU variant	: 0x3
CPU part	: 0xc08
CPU revision	: 2
--->8---

AFAIK is CPU variant 'r3' and CPU revision 'p2' for this cpuinfo.

Regards

Andreas Bießmann