[PATCH 11/14] drivers: firmware: psci: Allow OS Initiated suspend mode

[Vikas Sajjan]

Hi Mark,

On Mon, Jun 27, 2016 at 3:42 PM, Mark Rutland <mark.rutland at arm.com> wrote:
> On Fri, Jun 24, 2016 at 09:55:20AM +0530, Vikas Sajjan wrote:
>> On Thu, Jun 23, 2016 at 1:06 AM, Lina Iyer <lina.iyer at linaro.org> wrote:
>> > +static int __init psci_1_0_init(struct device_node *np)
>> > +{
>> > +       int ret;
>> > +
>> > +       ret = psci_0_2_init(np);
>> > +       if (ret)
>> > +               return ret;
>> > +
>> > +       /* Check if PSCI OSI mode is available */
>> > +       ret = psci_features(psci_function_id[PSCI_FN_CPU_SUSPEND]);
>> > +       if (ret & PSCI_1_0_OS_INITIATED) {
>> > +               ret = psci_features(PSCI_1_0_FN_SET_SUSPEND_MODE);
>> > +               if (!ret)
>> > +                       psci_has_osi_pd = true;
>>
>> IMHO, its better to have this done in psci_init_cpu_suspend() itself
>> for 2 reasons
>>
>> a] psci_init_cpu_suspend() already calls
>> psci_features(psci_function_id[PSCI_FN_CPU_SUSPEND])
>> b] by moving this in psci_init_cpu_suspend() we make this support
>> available even for ACPI platforms, since psci_acpi_init() calls
>> psci_probe() and this calls  psci_init_cpu_suspend() for
>> PSCI_VERSION_MAJOR(ver) >= 1
>
> For ACPI platforms it is necessary to go through a handshake to
> determine whether LPI can use OSI (see 6.2.11.2 in the ACPI 6.1 spec).
> So there will have to be some ACPI-specific code to determine whether
> OSI should be used.
>
> We will probably have to an ACPI-specific wrapper for
> psci_init_cpu_suspend to cater for that. I don't think that
> psci_init_cpu_suspend itself should be in charge of deciding whether to
> enable OSI.

True, I think you are referring to the function acpi_bus_osc_support()
which does the handing shaking.
Right, for ACPI platforms along with SET_SUSPEND_MODE feature, we
should also be depending on the handing shaking result to set the
psci_has_osi_pd flag.


>
> Thanks,
> Mark.

Thanks and Regards
Vikas Sajjan
Hewlett Packard Enterprise