Subject: [PATCH RFT 1/2] drivers: bus: check cci device tree node status

From: [email-masked] (Sudeep Holla)
Date: Thu, 08 Jan 2015 12:15:35 +0530

Hi Abhilash,

On Wednesday 10 December 2014 10:46 AM, Sudeep Holla wrote:
>
>
> On Wednesday 10 December 2014 09:55 AM, Abhilash Kesavan wrote:
>> Hi Sudeep,
>>
>> On Wed, Dec 10, 2014 at 9:44 AM, Sudeep Holla <[email-masked]> wrote:
>>> Hi Abhilash,
>>>
>>> On Wednesday 10 December 2014 09:31 AM, Abhilash Kesavan wrote:
>>>>
>>>> Hi,
>>>>
>>>> On Fri, Nov 28, 2014 at 8:20 PM, Abhilash Kesavan <[email-masked]>
>>>> wrote:
>>>>>
>>>>> The arm-cci driver completes the probe sequence even if the cci node is
>>>>> marked as disabled. Add a check in the driver to honour the cci status
>>>>> in the device tree.
>>>>>
>>>>> Signed-off-by: Abhilash Kesavan <[email-masked]>
>>>>
>>>>
>>>> This patch helps disable CCI on the Arndale Octa board thus resolving
>>>> some imprecise aborts seen on that board. Kindly review.
>>>>
>>>> Regards,
>>>> Abhilash
>>>>>
>>>>> ---
>>>>>     drivers/bus/arm-cci.c |    3 +++
>>>>>     1 file changed, 3 insertions(+)
>>>>>
>>>>> diff --git a/drivers/bus/arm-cci.c b/drivers/bus/arm-cci.c
>>>>> index 860da40..0ce5e2d 100644
>>>>> --- a/drivers/bus/arm-cci.c
>>>>> +++ b/drivers/bus/arm-cci.c
>>>>> @@ -1312,6 +1312,9 @@ static int cci_probe(void)
>>>>>            if (!np)
>>>>>                    return -ENODEV;
>>>>>
>>>>> +       if (!of_device_is_available(np))
>>>>> +               return -ENODEV;
>>>>> +
>>>
>>>
>>> IIUC, by this change you are disabling the MCPM boot protocol here.
>>> Is there any alternative boot protocol that works on this platform
>>> to boot all 8 cores ? Sorry by quick grep couldn't find one, hence
>>> so I am asking.
>>
>> Thanks for the reply.
>> On disabling MCPM, we will default to platsmp.c/firmware.c which boots
>> 4 cores as per Kevin's comment here[1]. This was the original behavior
>> before MCPM was enabled for all 5420 based SoCs.
>>
>
> Thanks for pointing that out. I assume the firmware can handle the
> alternate boot protocol and no more workarounds are needed especially
> when getting CPUIdle working in this mode.
>
> Anyways the patch makes sense irrespective how it works on exynos, so
> you can add,
>
> Acked-by: Sudeep Holla <[email-masked]>
>

What's the status of this patch. It was useful for me on vexpress for 
some testing. Please feel free to add

Tested-by: Sudeep Holla <[email-masked]>

if this is not yet queued.

Regards,
Sudeep