Errata Description: CPU A-005125 - SPR976 not found

[yepkris]

Hi All,

Recently we received an errata (CPU A-005125) from freescale, in which a workaround is given for resolving a system hang issue of e500 core. It is recomended to set SPR976[40:41] to b'10. However, we can not found this register in the PowerPC e500 Core Family Reference Manual.So could anybody please tell me what's the name of this SPR or how can I find it in any datasheet?

What's more, for the system hang, could anybody kindly tell me how to reproduce this issue? Thanks a lot.

-Kris.

[suchit_lepcha]

The SPR976 is a hidden register in e500v2. Its a rare condition.

[yepkris]

Hi Suchit,

That is to say we can not find the description of the SPR976 in the specs, right? In this case, is it correct to write b'10 to the SPR976[40:41] in the u-boot boot-up stage? or in the runtime (say, Linux) stage?

Thanks,

-Kris.

[suchit_lepcha · Accepted solution]

You are right. The description of SPR976 is not available  in e500v2 manual.This should be done as early as possible. Hence this has to be in the u-boot boot-up stage.

[yepkris]

Hi Suchit,

If we try to config this SPR in Linux init stage, will it bring more risks? Because the bootloader we use is not that easy to modify.

-Kris

[suchit_lepcha]

As the erratum says, the issue may occur while there are some transactions on PCI/PCIe/SRIO bus (for more details, please refer the erratum). If you are confident that there will be no transactions on PCI/PCIe/SRIO bus till Linux comes up, you may choose to apply workaround in Linux.

For example, the u-boot bootloader scans the PCI/PCIe bus and accordingly creates in/out bound windows. The system may hit the erratum if PCI/PCIe transactions start before Linux comes up.

[yepkris]

Hi Suchit,

Got it. Thx a lot!

-Kris

[murugeshpitchai]

Hi Kris,

I am also in  your boat ! Need to implement this bit setting. But as you mentioned I am not able to see the possible way we can define this register in code. I see people have suggested to implement it in u-boot. Could you please elaborate more on this ? Is there no way to define this in code ?

BTW, I am working for a router.