[PATCH 2/2] arm64: dts: Add PMU node for APM X-Gene Storm SOC

[Dann Frazier]

On Tue, Jun 24, 2014 at 1:00 AM, Ming Lei <ming.lei at canonical.com> wrote:
> Hi Jon and Vinayak,
>
> On Tue, Jun 24, 2014 at 11:42 AM, Jon Masters <jcm at redhat.com> wrote:
>> On 06/23/2014 10:47 PM, Ming Lei wrote:
>>
>>> On Thu, Mar 20, 2014 at 5:47 PM, Vinayak Kale <vkale at apm.com> wrote:
>>>> This patch adds the PMU device tree node for APM X-Gene Storm SOC.
>>>>
>>>> Please note that this patch has dependancy on a GIC driver patch [1] which is
>>>> yet to be approved by maintainers.
>>>>
>>>> [1]- https://lkml.org/lkml/2014/2/27/605
>>>> (irqchip:gic: change access of gicc_ctrl register to read modify write)
>>
>>> No matter if Feng Kan's gic patch is applied or not, perf(PMU)
>>> still can't work well with your patch, and the failure[1] will be
>>> triggered when 'perf top' is started.
>>>
>>> The failure happened during the 1st pmu overflow interrupt.
>>>
>>> I test several mustang boards, and all has the problem with
>>> upstream kernel.
>>
>> Note that the GIC bypass register config is set by the firmware and this
>> only preserves the original setting, so you could be running an older
>> firmware (such as U-Boot). On our (UEFI-enabled systems, complete with
>> correct patch) perf top runs correctly without any such problems.
>
> I am wondering if it is related with boot or firmware. We have a board
> which is running APM internal 3.12 based kernel, and perf(pmu) works
> well. But if I just replace the 3.12 based kernel with upstream kernel
> and keep others(boot, kernel parameter, fs, ....) not changed, then
> the problem still can happen.

fyi, newer firmware is confirmed to fix this issue on u-boot based platforms.
Tested-by: dann frazier <dann.frazier at canonical.com>