imx6q restart is broken

[Catalin Marinas]

On 15 August 2012 22:44, Russell King - ARM Linux
<linux at arm.linux.org.uk> wrote:
> On Wed, Aug 15, 2012 at 10:07:47AM -0500, Rob Herring wrote:
>> I think I am seeing a similar problem on highbank with a v7 only build.
>>
>> >From what I've debugged, restart hangs for me on the L2x0 spinlock
>> during a writel. Changing the writel to writel_relaxed in the restart
>> hook fixes the problem. This skips barriers in the writel and for the
>> spinlock. However, I'm still puzzled as cpu_relax on the secondary cores
>> should not be doing a dmb in my case on a v7 only build.
>
> Well, I had the idea of only doing a dmb() once every N loops, but I don't
> think we can sensibly introduce such a change into the mainline kernel.
> (How would cpu_relax() know it's being used in a loop?)

It doesn't really need to know. We can say that every X calls to
cpu_relax() should result in a dmb and we can make the counter
per-cpu. This would ensure the write-buffer draining which was the aim
of this dmb.

-- 
Catalin