Re: [PATCH] arm: Add Arm Erratum 773769 for Large data RAM latency.

[Nicolas Pitre]

On Wed, 8 Jan 2014, Doug Anderson wrote:

> Hi,
> 
> On Wed, Jan 8, 2014 at 11:20 AM, Russell King - ARM Linux
> > No, we're saying to put the work-around in the boot loader, not the kernel.
> 
> Unfortunately the resume path of the firmware runs from Read Only 
> firmware code (yes, it sucks), so it's not totally trivial to fix. It 
> would be possible for someone to unscrew their write protect switch 
> and update their RO firmware, but that doesn't help the average user.

[...]

> I'd guess that the way forward is:
> 
> * Land kernel workaround locally in Chromium tree
> 
> * I'll try to land FW change locally in at least one Chromium branch.
> If we were to get a new RO build ever (seems unlikely at this point)
> it would be fixed for upstream kernels.  If we were to get a new RW
> build (seems unlikely, but at least less unlikely) it would be fixed
> if someone landed a kernel patch to save/restore this register across
> suspend/resume.
> 
> * If Joe Upstream wants to run an upstream kernel on some type of
> exynos5250 product (Samsung ARM Chromebook, HP Chromebook 11, Nexus 10
> are the ones I know of) then he will deal with the small number of
> crashes or figure out a solution.

If Joe Upstream wants to run an upstream kernel, doesn't he have to 
unscrew his write protect switch first, at which point the RO firmware 
can be updated as well?


Nicolas
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