On Tuesday, December 18, 2012 09:10:41 AM Toshi Kani wrote:
> On Tue, 2012-12-18 at 02:48 +0100, Rafael J. Wysocki wrote:
> > On Monday, December 17, 2012 05:08:17 PM Toshi Kani wrote:
> > > On Thu, 2012-12-13 at 23:17 +0100, Rafael J. Wysocki wrote:
> > > > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> > > >
> > >
> > > (snip)
> > >
> > > > struct acpi_device_ops {
> > > > Index: linux/drivers/acpi/scan.c
> > > > ===================================================================
> > > > --- linux.orig/drivers/acpi/scan.c
> > > > +++ linux/drivers/acpi/scan.c
> > > > @@ -494,7 +494,8 @@ static int acpi_bus_match(struct device
> > > > struct acpi_device *acpi_dev = to_acpi_device(dev);
> > > > struct acpi_driver *acpi_drv = to_acpi_driver(drv);
> > > >
> > > > - return !acpi_match_device_ids(acpi_dev, acpi_drv->ids);
> > > > + return acpi_dev->bus_ops.acpi_op_match
> > > > + && !acpi_match_device_ids(acpi_dev, acpi_drv->ids);
> > > > }
> > > >
> > > > static int acpi_device_uevent(struct device *dev, struct kobj_uevent_env *env)
> > > > @@ -1418,6 +1419,17 @@ static int acpi_bus_remove(struct acpi_d
> > > > return 0;
> > > > }
> > > >
> > > > +/*
> > > > + * acpi_hot_add_bind - Bind _ADR-based devices on hot-add.
> > > > + * @device: ACPI device node to bind.
> > > > + */
> > > > +static void acpi_hot_add_bind(struct acpi_device *device)
> > > > +{
> > > > + if (device->flags.bus_address
> > > > + && device->parent && device->parent->ops.bind)
> > > > + device->parent->ops.bind(device);
> > > > +}
> > > > +
> > > > static int acpi_add_single_object(struct acpi_device **child,
> > > > acpi_handle handle, int type,
> > > > unsigned long long sta,
> > > > @@ -1490,13 +1502,8 @@ static int acpi_add_single_object(struct
> > > >
> > > > result = acpi_device_register(device);
> > > >
> > > > - /*
> > > > - * Bind _ADR-Based Devices when hot add
> > > > - */
> > > > - if (device->flags.bus_address) {
> > > > - if (device->parent && device->parent->ops.bind)
> > > > - device->parent->ops.bind(device);
> > > > - }
> > >
> > > I think the original code above is hot-add only because ops.bind is not
> > > set at boot since the acpi_pci driver has not been registered yet. It
> > > seems that acpi_pci_bridge_scan() called from acpi_pci_root_add() takes
> > > care of the binding.
> >
> > Ah, I see the problem. During boot the PCI root bridge driver is not present
> > yet when all struct acpi_device "devices" are registered, so their parents'
> > .bind() callbacks are all empty, so the code above has no effect.
> >
> > But say we're doing a PCI root bridge hotplug, in which case the driver is
> > present, so acpi_pci_bind() will be executed both from acpi_pci_bridge_scan()
> > and from here, won't it?
>
> Right.
>
>
> > OK, this needs to be addressed.
> >
> > > This brings me a question for acpi_bus_probe_start() below...
> > >
> > >
> > > > + if (device->bus_ops.acpi_op_match)
> > > > + acpi_hot_add_bind(device);
> > > >
> > > > end:
> > > > if (!result) {
> > > > @@ -1522,6 +1529,7 @@ static void acpi_bus_add_power_resource(
> > > > struct acpi_bus_ops ops = {
> > > > .acpi_op_add = 1,
> > > > .acpi_op_start = 1,
> > > > + .acpi_op_match = 1,
> > > > };
> > > > struct acpi_device *device = NULL;
> > > >
> > > > @@ -1574,9 +1582,9 @@ static acpi_status acpi_bus_check_add(ac
> > > > void *context, void **return_value)
> > > > {
> > > > struct acpi_bus_ops *ops = context;
> > > > + struct acpi_device *device = NULL;
> > > > int type;
> > > > unsigned long long sta;
> > > > - struct acpi_device *device;
> > > > acpi_status status;
> > > > int result;
> > > >
> > > > @@ -1596,52 +1604,86 @@ static acpi_status acpi_bus_check_add(ac
> > > > return AE_CTRL_DEPTH;
> > > > }
> > > >
> > > > - /*
> > > > - * We may already have an acpi_device from a previous enumeration. If
> > > > - * so, we needn't add it again, but we may still have to start it.
> > > > - */
> > > > - device = NULL;
> > > > acpi_bus_get_device(handle, &device);
> > > > if (ops->acpi_op_add && !device) {
> > > > - acpi_add_single_object(&device, handle, type, sta, ops);
> > > > - /* Is the device a known good platform device? */
> > > > - if (device
> > > > - && !acpi_match_device_ids(device, acpi_platform_device_ids))
> > > > - acpi_create_platform_device(device);
> > > > - }
> > > > -
> > > > - if (!device)
> > > > - return AE_CTRL_DEPTH;
> > > > + struct acpi_bus_ops add_ops = *ops;
> > > >
> > > > - if (ops->acpi_op_start && !(ops->acpi_op_add)) {
> > > > - status = acpi_start_single_object(device);
> > > > - if (ACPI_FAILURE(status))
> > > > + add_ops.acpi_op_match = 0;
> > > > + acpi_add_single_object(&device, handle, type, sta, &add_ops);
> > > > + if (!device)
> > > > return AE_CTRL_DEPTH;
> > > > +
> > > > + device->bus_ops.acpi_op_match = 1;
> > > > }
> > > >
> > > > if (!*return_value)
> > > > *return_value = device;
> > > > +
> > > > return AE_OK;
> > > > }
> > > >
> > > > +static acpi_status acpi_bus_probe_start(acpi_handle handle, u32 lvl,
> > > > + void *context, void **not_used)
> > > > +{
> > > > + struct acpi_bus_ops *ops = context;
> > > > + acpi_status status = AE_OK;
> > > > + struct acpi_device *device;
> > > > + unsigned long long sta_not_used;
> > > > + int type_not_used;
> > > > +
> > > > + /*
> > > > + * Ignore errors ignored by acpi_bus_check_add() to avoid terminating
> > >
> > > "ignore" seems duplicated.
> >
> > It is not. This is supposed to mean that the errors previously ignored by
> > acpi_bus_check_add() should be ignored here as well.
>
> Oh, I see. Thanks for the clarification.
>
>
> > > > + * namespace walks prematurely.
> > > > + */
> > > > + if (acpi_bus_type_and_status(handle, &type_not_used, &sta_not_used))
> > > > + return AE_OK;
> > > > +
> > > > + if (acpi_bus_get_device(handle, &device))
> > > > + return AE_CTRL_DEPTH;
> > > > +
> > > > + if (ops->acpi_op_add) {
> > > > + if (!acpi_match_device_ids(device, acpi_platform_device_ids)) {
> > > > + /* This is a known good platform device. */
> > > > + acpi_create_platform_device(device);
> > > > + } else {
> > > > + int ret = device_attach(&device->dev);
> > > > + acpi_hot_add_bind(device);
> > >
> > > Since acpi_pci_root_add() is called by device_attach(), I think this
> > > acpi_hot_add_bind() calls .bind() of a device at boot since its .bind()
> > > may be set. Is that correct? If so, how does it coordinate with the
> > > bind procedure in acpi_pci_bridge_scan()?
> >
> > It actually doesn't.
> >
> > However, the $subject patch doesn't change this particular aspect of the
> > original behavior, because with it applied the PCI root bridge driver is still
> > not present when the device_attach() above is executed for all objects in the
> > given namespace scope, so the .bind() callbacks should all be empty. In other
> > words, it doesn't change the boot case.
> >
> > It also reproduces the original behavior in the hotplug case which may not be
> > correct. Patch [2/6], however, kind of changes the boot case into the hotplug
> > case and things start to get ugly.
>
> Yes, I was concerned with the behavior when patch [2/6] applied. It is
> actually a good thing that this hotplug issue is now exposed in the boot
> path. This means that boot and hot-add paths are consistent. So, we
> just need to fix it.
>
>
> > Well, what about calling acpi_hot_add_bind() from acpi_bus_check_add(),
> > right after doing the acpi_add_single_object()? It would avoid calling
> > acpi_pci_bind() twice for the same device during root bridge hotplug too,
> > because in that case acpi_pci_root_add() will be called after all of these
> > acpi_hot_add_bind() calls. At the same time if a single device is
> > hot-added and its parent happens to have .bind() set, it will be run
> > from acpi_bus_check_add().
>
> I may be missing something here, but in case of root bridge hot-add, I
> think acpi_pci_root_add() still calls .bind() after acpi_bus_check_add()
> called it. So, it's called twice, isn't it?
No, it isn't. The reason is that the .bind pointers of all devices below the
root bridge are populated from within acpi_pci_root_add() and are NULL before
it is called. Therefore they are NULL when acpi_bus_check_add() checks them.
Of course, I'm referring to this patch:
https://patchwork.kernel.org/patch/1889821/
After this and [2/6] (https://patchwork.kernel.org/patch/1884701/) have been
applied, it is quite easy to verify that acpi_pci_bind() is called exactly once
for each PCI device during boot (just add a debug printk to that function) and
the same should happen during root bridge hotplug.
> We need to decide which module is responsible for calling .bind(). I
> think it should be the ACPI scan module, not the ACPI PCI root bridge
> driver, because:
> - bind() needs to be called when _ADR device is added. The ACPI scan
> module can scan any devices, while the PCI root driver can only scan
> when it is added.
> - acpi_bus_remove() calls unbind() at hot-remove. The same module
> should be responsible for both bind() and unbind() handling.
> - It is cleaner to keep struct acpi_device_ops interface to be called
> by the ACPI core.
I agree with that. :-)
Moreover, I don't think we need acpi_pci_bind() and acpi_pci_unbind() at all.
> So, I would propose the following changes.
>
> - Move the acpi_hot_add_bind() call back to the original place after
> the device_attach() call.
> - Rename the name of acpi_hot_add_bind() to something like
> acpi_bind_adr_device() since it is no longer hot-add only (and is
> specific to _ADR devices).
> - Create its pair function, acpi_unbind_adr_device(), which is called
> from acpi_bus_remove(). When a constructor interface is introduced, its
> destructor should be introduced as well.
> - Remove the binding procedure from acpi_pci_root_add(). This should
> be done in patch [2/6].
Well, what about moving the code from acpi_pci_bind()/acpi_pci_unbind()
somewhere else and removing those things altogether?
Rafael
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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