Messages in this thread | | | Subject | Re: [PATCH v5 2/5] ACPI / processor_idle: Add support for Low Power Idle(LPI) states | From | Sudeep Holla <> | Date | Thu, 19 May 2016 14:26:29 +0100 |
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On 18/05/16 20:13, Prakash, Prashanth wrote: > > > On 5/18/2016 11:37 AM, Sudeep Holla wrote: >> >> >> On 17/05/16 18:46, Prakash, Prashanth wrote: >>> Hi Sudeep, >>> >>> On 5/11/2016 9:37 AM, Sudeep Holla wrote: >>>> + >>>> +static int acpi_processor_get_lpi_info(struct acpi_processor *pr) >>>> +{ >>>> + int ret, i; >>>> + struct acpi_lpi_states_array *info; >>>> + struct acpi_device *d = NULL; >>>> + acpi_handle handle = pr->handle, pr_ahandle; >>>> + acpi_status status; >>>> + >>>> + if (!osc_pc_lpi_support_confirmed) >>>> + return -EOPNOTSUPP; >>>> + >>>> + max_leaf_depth = 0; >>>> + if (!acpi_has_method(handle, "_LPI")) >>>> + return -EINVAL; >>>> + flat_state_cnt = 0; >>>> + >>>> + while (ACPI_SUCCESS(status = acpi_get_parent(handle, &pr_ahandle))) { >>>> + if (!acpi_has_method(handle, "_LPI")) >>>> + continue; >>>> + >>>> + acpi_bus_get_device(handle, &d); >>>> + if (!strcmp(acpi_device_hid(d), ACPI_PROCESSOR_CONTAINER_HID)) >>>> + break; >>>> + >>>> + max_leaf_depth++; >>>> + handle = pr_ahandle; >>>> + } >>>> + >>> In the above loop, we break when we find a device with HID == >>> ACPI_PROCESSOR_CONTAINER_HID. Shouldn't we continue to parse as long as the >>> parent HID == ACPI_PROCESSOR_CONTAINER_HID? This is required to make sure we >>> parse states in levels higher than cluster level in processor hierarchy. >>> >> >> Yes, thanks for pointing that out. With just clusters in _LPI on my dev >> board, I missed it. >> > Same reason, I failed to notice it all this time :)
No worries.
>>> Also, I think it might be safe to break out of the loop if we didn't find >>> _LPI package, instead of continuing. Given the presence of LPI entry: >>> "Enabled Parent State", I can't think of a non-ambiguous scenario where we >>> might find LPI packages in state N and N+2, but not in N+1, as we will not >>> be able to figure out which state in N enables which states in N+2. >>> Thoughts? >> >> Though I admit I haven't thought in detail on how to deal with the >> asymmetric topology, but that was the reason why I continue instead of >> breaking. >> >> Excerpts from the spec: "... This example is symmetric but that is not a >> requirement. For example, a system may contain a different number of >> processors in different containers or an asymmetric hierarchy where one >> side of the topology tree is deeper than another...." >> > If it addresses asymmetric topology, sure we can keep as it doesn't impact other > scenarios. Also, we need to set handle=pr_ahandle prior to the continue statement. >
Yes I noticed it yesterday, the more I think, I feel we can break out of the loop. At any level, we need to have container nodes and that must contain _LPI irrespective of asymmetricity. So you were right. I have fixed accordingly and have pushed out on my branch.
-- Regards, Sudeep
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