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    SubjectRe: [RFC PATCH 2/6] ACPI: Reference devices in ACPI Power Resource
    Date
    On Tuesday, February 14, 2012, Zhang Rui wrote:
    > On 一, 2012-02-13 at 21:48 +0100, Rafael J. Wysocki wrote:
    > > On Monday, February 13, 2012, Lin Ming wrote:
    > > > From: Zhang Rui <rui.zhang@intel.com>
    > > >
    > > > ACPI Power Resource can power on/off a couple of devices.
    > > > Introduce interfaces to register/unregister a device to/from
    > > > an ACPI Power Resource.
    > > >
    > > > Signed-off-by: Zhang Rui <rui.zhang@intel.com>
    > > > ---
    > > > drivers/acpi/power.c | 128 +++++++++++++++++++++++++++++++++++++++++++++++
    > > > include/acpi/acpi_bus.h | 2 +
    > > > 2 files changed, 130 insertions(+), 0 deletions(-)
    > > >
    > > > diff --git a/drivers/acpi/power.c b/drivers/acpi/power.c
    > > > index 0d681fb..a7e2305 100644
    > > > --- a/drivers/acpi/power.c
    > > > +++ b/drivers/acpi/power.c
    > > > @@ -84,10 +84,25 @@ struct acpi_power_resource {
    > > > u32 order;
    > > > unsigned int ref_count;
    > > > struct mutex resource_lock;
    > > > + struct list_head devices; /* list for devices powered by this PR */
    > > > };
    > > >
    > > > static struct list_head acpi_power_resource_list;
    > > >
    > > > +/*
    > > > + * When a power resource is turned on, all the devices are put to an uninitialized
    > > > + * state although their ACPI states are still D0.
    > > > + * To handle this, we need to keep a list of all devices powered by the power resource,
    > > > + * and resume all of them.
    > > > + * Currently, we only support this case:
    > > > + * 1) multiple devices share the same power resoruce,
    > > > + * 2) One device uses One Power Resource ONLY.
    > >
    > > This is incorrect. We actually support all combinations.
    >
    > Agreed.
    >
    > > However, we don't
    > > generally support checking what devices depend on the given power resource.
    > >
    > Yes.
    > But all the code in this patch is for runtime D3_COLD support only.
    > At least for the BIOS code on hand, a device that support runtime
    > D3_COLD uses one ACPI Power Resource only.
    > We can add the support for all combinations if there are such kind of
    > BIOS in the market, which I do not think there would be.
    >
    > Besides, as a RFC version, I do not want to make a over designed
    > proposal at the beginning.
    >
    > > > + */
    > > > +struct acpi_powered_device {
    > > > + struct list_head node;
    > > > + struct device *dev;
    > > > +};
    > > > +
    > > > /* --------------------------------------------------------------------------
    > > > Power Resource Management
    > > > -------------------------------------------------------------------------- */
    > > > @@ -455,6 +470,118 @@ int acpi_disable_wakeup_device_power(struct acpi_device *dev)
    > > > Device Power Management
    > > > -------------------------------------------------------------------------- */
    > > >
    > > > +int acpi_power_resource_register_device(struct device *dev, acpi_handle handle)
    > > > +{
    > > > + struct acpi_power_resource *resource;
    > > > + struct acpi_device *acpi_dev, *res_dev;
    > > > + acpi_handle res_handle = NULL;
    > > > + struct acpi_powered_device *apd;
    > > > + int i;
    > > > + int ret;
    > > > +
    > > > + if (!handle || !dev)
    > > > + return -EINVAL;
    > > > +
    > > > + ret = acpi_bus_get_device(handle, &acpi_dev);
    > > > + if (ret)
    > > > + goto no_power_resource;
    > > > +
    > > > + if (!acpi_dev->power.flags.power_resources)
    > > > + goto no_power_resource;
    > > > +
    > > > + for (i = 0; i <= ACPI_STATE_D3; i++) {
    > > > + struct acpi_device_power_state *ps = &acpi_dev->power.states[i];
    > > > +
    > > > + if (!ps->flags.valid)
    > > > + continue;
    > > > +
    > > > + if (ps->resources.count > 1)
    > > > + return 0;
    > > > +
    > > > + if (!res_handle)
    > > > + res_handle = ps->resources.handles[0];
    > > > + else if (res_handle != ps->resources.handles[0])
    > > > + return 0;
    > > > + }
    > >
    > > I'm not sure what the above checks are needed for. It seems that this function
    > > will only be called from acpi_bus_add_power_resource() (which needs to be
    > > modified for this purpose, BTW), so it doesn't need to check all those things
    > > (those checks have been made already).
    > >
    > No. These two APIs are introduced to support the runtime D3_COLD remote
    > wakeup. And they should be invoked by drivers, either in driver code or
    > via bus layer code.
    >
    > Say, ATA port, who has _PR3 in its ACPI node, knows that it can enter
    > D3_COLD at run time, and it supports remote wakeup in D3_COLD because it
    > has _S0W (return value 4).
    > When remote wakeup event is triggered, there is an ACPI event sent to
    > the ATA controller/port, which sets the ATA controller/port back to D0
    > state.
    > At this time, what we actually need is to resume the ZPODD, rather than
    > the ATA controller/port. To follow the runtime PM model (runtime resume
    > starts from leaf devices),

    Well, this isn't the case. Parents are always resumed first.

    > ATA code can use these two APIs to tell ACPI
    > to runtime resume ZPODD device directly, because ZPODD is powered by
    > this Power Resource as well.

    I'm not exactly sure what you're trying to achieve and what you mean by
    "resume a device directly"? Do you want to run the device's resume
    callback at the time when another device is being resumed?

    Rafael
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