Time to get rid of CPU6 ERRATA on powerpc/8xx ?

[Joakim Tjernlund]

On Sun, 2018-01-07 at 17:23 +0100, christophe leroy wrote:
> CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.
> 
> 
> Today, Linux kernel includes a workaround for CPU6 ERRATA on the 8xx
> powerpc.
> 
> This ERRATA exists on the 801, the 823, the 855/860 before revision C.0
> It doesn't concern any modern versions of the 8xx, neither the 860 past
> and including rev C.0, nor the 866 nor the 885
> 
> This workaround complicates the TLBmiss and TLBerror handlers and make
> the code more and more unreadable.
> 
> Since this workaround addresses very old versions of the 8xx, I'd like
> to get rid of it. Do you see any good reason to keep it today ? If not I
> will come with a cleanup patch in the coming weeks.
> 
> Another alternative would be to keep that workaround separated from the
> rest of the code (ie using different registers to avoid/limit code
> nesting), it would add a few cycles but would increase readability while
> keeping the ERRATA in, allthought my preference goes to a complete
> removal of the workaround.
> 
> So, thanks to let me know your opinion on that.

Having done work on TLB Miss/Error, I agree the CPU6 errata is a pain.
On all our 8xx (86x/850) we never had to use this errata so I am in favour for
removing CPU6 Errata from recent kernels.

  Jocke