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Date: Sat, 6 Jun 2020 17:45:10 +0200
From: Hans de Goede <hdegoede@...hat.com>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>,
ACPI Devel Maling List <linux-acpi@...r.kernel.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>,
Len Brown <lenb@...nel.org>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Mika Westerberg <mika.westerberg@...ux.intel.com>,
youling257@...il.com, LKML <linux-kernel@...r.kernel.org>,
Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH] ACPI: PM: Avoid using power resources if there are none
for D0
Hi,
On 6/4/20 7:22 PM, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> As recently reported, some platforms provide a list of power
> resources for device power state D3hot, through the _PR3 object,
> but they do not provide a list of power resources for device power
> state D0.
>
> Among other things, this causes acpi_device_get_power() to return
> D3hot as the current state of the device in question if all of the
> D3hot power resources are "on", because it sees the power_resources
> flag set and calls acpi_power_get_inferred_state() which finds that
> D3hot is the shallowest power state with all of the associated power
> resources turned "on", so that's what it returns. Moreover, that
> value takes precedence over the acpi_dev_pm_explicit_get() return
> value, because it means a deeper power state. The device may very
> well be in D0 physically at that point, however.
>
> Moreover, the presence of _PR3 without _PR0 for a given device
> means that only one D3-level power state can be supported by it.
> Namely, because there are no power resources to turn "off" when
> transitioning the device from D0 into D3cold (which should be
> supported since _PR3 is present), the evaluation of _PS3 should
> be sufficient to put it straight into D3cold, but this means that
> the effect of turning "on" the _PR3 power resources is unclear,
> so it is better to avoid doing that altogether. Consequently,
> there is no practical way do distinguish D3cold from D3hot for
> the device in question and the power states of it can be labeled
> so that D3hot is the deepest supported one (and Linux assumes
> that putting a device into D3hot via ACPI may cause power to be
> removed from it anyway, for legacy reasons).
>
> To work around the problem described above modify the ACPI
> enumeration of devices so that power resources are only used
> for device power management if the list of D0 power resources
> is not empty and make it mart D3cold as supported only if that
> is the case and the D3hot list of power resources is not empty
> too.
>
> Fixes: ef85bdbec444 ("ACPI / scan: Consolidate extraction of power resources lists")
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=205057
> Link: https://lore.kernel.org/linux-acpi/20200603194659.185757-1-hdegoede@redhat.com/
> Reported-by: Hans de Goede <hdegoede@...hat.com>
> Cc: 3.10+ <stable@...r.kernel.org> # 3.10+
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Thank you.
I've tested this and I can confirm that it fixes the issue:
Tested-by: Hans de Goede <hdegoede@...hat.com>
I've also looked at the code and it looks good to me:
Reviewed-by: Hans de Goede <hdegoede@...hat.com>
Regards,
Hans
> ---
> drivers/acpi/device_pm.c | 2 +-
> drivers/acpi/scan.c | 28 +++++++++++++++++++---------
> 2 files changed, 20 insertions(+), 10 deletions(-)
>
> Index: linux-pm/drivers/acpi/scan.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/scan.c
> +++ linux-pm/drivers/acpi/scan.c
> @@ -919,12 +919,9 @@ static void acpi_bus_init_power_state(st
>
> if (buffer.length && package
> && package->type == ACPI_TYPE_PACKAGE
> - && package->package.count) {
> - int err = acpi_extract_power_resources(package, 0,
> - &ps->resources);
> - if (!err)
> - device->power.flags.power_resources = 1;
> - }
> + && package->package.count)
> + acpi_extract_power_resources(package, 0, &ps->resources);
> +
> ACPI_FREE(buffer.pointer);
> }
>
> @@ -971,14 +968,27 @@ static void acpi_bus_get_power_flags(str
> acpi_bus_init_power_state(device, i);
>
> INIT_LIST_HEAD(&device->power.states[ACPI_STATE_D3_COLD].resources);
> - if (!list_empty(&device->power.states[ACPI_STATE_D3_HOT].resources))
> - device->power.states[ACPI_STATE_D3_COLD].flags.valid = 1;
>
> - /* Set defaults for D0 and D3hot states (always valid) */
> + /* Set the defaults for D0 and D3hot (always supported). */
> device->power.states[ACPI_STATE_D0].flags.valid = 1;
> device->power.states[ACPI_STATE_D0].power = 100;
> device->power.states[ACPI_STATE_D3_HOT].flags.valid = 1;
>
> + /*
> + * Use power resources only if the D0 list of them is populated, because
> + * some platforms may provide _PR3 only to indicate D3cold support and
> + * in those cases the power resources list returned by it may be bogus.
> + */
> + if (!list_empty(&device->power.states[ACPI_STATE_D0].resources)) {
> + device->power.flags.power_resources = 1;
> + /*
> + * D3cold is supported if the D3hot list of power resources is
> + * not empty.
> + */
> + if (!list_empty(&device->power.states[ACPI_STATE_D3_HOT].resources))
> + device->power.states[ACPI_STATE_D3_COLD].flags.valid = 1;
> + }
> +
> if (acpi_bus_init_power(device))
> device->flags.power_manageable = 0;
> }
> Index: linux-pm/drivers/acpi/device_pm.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/device_pm.c
> +++ linux-pm/drivers/acpi/device_pm.c
> @@ -186,7 +186,7 @@ int acpi_device_set_power(struct acpi_de
> * possibly drop references to the power resources in use.
> */
> state = ACPI_STATE_D3_HOT;
> - /* If _PR3 is not available, use D3hot as the target state. */
> + /* If D3cold is not supported, use D3hot as the target state. */
> if (!device->power.states[ACPI_STATE_D3_COLD].flags.valid)
> target_state = state;
> } else if (!device->power.states[state].flags.valid) {
>
>
>
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