Re: [PATCH v3 01/11] ACPI: delay enumeration of devices with a _DEP pointing to an INT3472 device

Hans de Goede
2021-10-13T18:24:22Z

Hi,

On 10/13/21 7:29 PM, Rafael J. Wysocki wrote:
> On Sun, Oct 10, 2021 at 8:57 PM Hans de Goede <hdegoede@redhat.com> wrote:
>>
>> The clk and regulator frameworks expect clk/regulator consumer-devices
>> to have info about the consumed clks/regulators described in the device's
>> fw_node.
>>
>> To work around cases where this info is not present in the firmware tables,
>> which is often the case on x86/ACPI devices, both frameworks allow the
>> provider-driver to attach info about consumers to the clks/regulators
>> when registering these.
>>
>> This causes problems with the probe ordering wrt drivers for consumers
>> of these clks/regulators. Since the lookups are only registered when the
>> provider-driver binds, trying to get these clks/regulators before then
>> results in a -ENOENT error for clks and a dummy regulator for regulators.
>>
>> One case where we hit this issue is camera sensors such as e.g. the OV8865
>> sensor found on the Microsoft Surface Go. The sensor uses clks, regulators
>> and GPIOs provided by a TPS68470 PMIC which is described in an INT3472
>> ACPI device. There is special platform code handling this and setting
>> platform_data with the necessary consumer info on the MFD cells
>> instantiated for the PMIC under: drivers/platform/x86/intel/int3472.
>>
>> For this to work properly the ov8865 driver must not bind to the I2C-client
>> for the OV8865 sensor until after the TPS68470 PMIC gpio, regulator and
>> clk MFD cells have all been fully setup.
>>
>> The OV8865 on the Microsoft Surface Go is just one example, all X86
>> devices using the Intel IPU3 camera block found on recent Intel SoCs
>> have similar issues where there is an INT3472 HID ACPI-device, which
>> describes the clks and regulators, and the driver for this INT3472 device
>> must be fully initialized before the sensor driver (any sensor driver)
>> binds for things to work properly.
>>
>> On these devices the ACPI nodes describing the sensors all have a _DEP
>> dependency on the matching INT3472 ACPI device (there is one per sensor).
>>
>> This allows solving the probe-ordering problem by delaying the enumeration
>> (instantiation of the I2C-client in the ov8865 example) of ACPI-devices
>> which have a _DEP dependency on an INT3472 device.
>>
>> The new acpi_dev_ready_for_enumeration() helper used for this is also
>> exported because for devices, which have the enumeration_by_parent flag
>> set, the parent-driver will do its own scan of child ACPI devices and
>> it will try to enumerate those during its probe(). Code doing this such
>> as e.g. the i2c-core-acpi.c code must call this new helper to ensure
>> that it too delays the enumeration until all the _DEP dependencies are
>> met on devices which have the new honor_deps flag set.
>>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> ---
>> drivers/acpi/scan.c | 36 ++++++++++++++++++++++++++++++++++--
>> include/acpi/acpi_bus.h | 5 ++++-
>> 2 files changed, 38 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
>> index 5b54c80b9d32..efee6ee91c8f 100644
>> --- a/drivers/acpi/scan.c
>> +++ b/drivers/acpi/scan.c
>> @@ -796,6 +796,12 @@ static const char * const acpi_ignore_dep_ids[] = {
>> NULL
>> };
>>
>> +/* List of HIDs for which we honor deps of matching ACPI devs, when checking _DEP lists. */
>> +static const char * const acpi_honor_dep_ids[] = {
>> + "INT3472", /* Camera sensor PMIC / clk and regulator info */
>> + NULL
>> +};
>> +
>> static struct acpi_device *acpi_bus_get_parent(acpi_handle handle)
>> {
>> struct acpi_device *device = NULL;
>> @@ -1757,8 +1763,12 @@ static void acpi_scan_dep_init(struct acpi_device *adev)
>> struct acpi_dep_data *dep;
>>
>> list_for_each_entry(dep, &acpi_dep_list, node) {
>> - if (dep->consumer == adev->handle)
>> + if (dep->consumer == adev->handle) {
>> + if (dep->honor_dep)
>> + adev->flags.honor_deps = 1;
>
> Any concerns about doing
>
> adev->flags.honor_deps = dep->honor_dep;
>
> here?

The idea is to set adev->flags.honor_deps even if the device has
multiple deps and only one of them has the honor_dep flag set.

If we just do:

adev->flags.honor_deps = dep->honor_dep;

Then adev->flags.honor_deps ends up having the honor_dep
flag of the last dependency checked.

>
>> +
>> adev->dep_unmet++;
>> + }
>> }
>> }
>>
>> @@ -1962,7 +1972,7 @@ static u32 acpi_scan_check_dep(acpi_handle handle, bool check_dep)
>> for (count = 0, i = 0; i < dep_devices.count; i++) {
>> struct acpi_device_info *info;
>> struct acpi_dep_data *dep;
>> - bool skip;
>> + bool skip, honor_dep;
>>
>> status = acpi_get_object_info(dep_devices.handles[i], &info);
>> if (ACPI_FAILURE(status)) {
>> @@ -1971,6 +1981,7 @@ static u32 acpi_scan_check_dep(acpi_handle handle, bool check_dep)
>> }
>>
>> skip = acpi_info_matches_ids(info, acpi_ignore_dep_ids);
>> + honor_dep = acpi_info_matches_ids(info, acpi_honor_dep_ids);
>> kfree(info);
>>
>> if (skip)
>> @@ -1984,6 +1995,7 @@ static u32 acpi_scan_check_dep(acpi_handle handle, bool check_dep)
>>
>> dep->supplier = dep_devices.handles[i];
>> dep->consumer = handle;
>> + dep->honor_dep = honor_dep;
>>
>> mutex_lock(&acpi_dep_list_lock);
>> list_add_tail(&dep->node , &acpi_dep_list);
>> @@ -2071,6 +2083,9 @@ static acpi_status acpi_bus_check_add_2(acpi_handle handle, u32 lvl_not_used,
>>
>> static void acpi_default_enumeration(struct acpi_device *device)
>> {
>> + if (!acpi_dev_ready_for_enumeration(device))
>> + return;
>
> I'm not sure about this.
>
> First of all, this adds an acpi_device_is_present() check here which
> potentially is a change in behavior and I'm not sure how it is related
> to the other changes in this patch (it is not mentioned in the
> changelog AFAICS).
>
> I'm saying "potentially", because if we get here at all,
> acpi_device_is_present() has been evaluated already by
> acpi_bus_attach().

Right the idea was that for this code-path the extra
acpi_device_is_present() check is a no-op since the only
caller of acpi_default_enumeration() has already done
that check before calling acpi_default_enumeration(),
where as the is_present check is useful for users outside
of the ACPI core code, like e.g. the i2c ACPI enumeration
code.

Although I see this is also called from
acpi_generic_device_attach which comes into play when there
is devicetree info embedded inside the ACPI tables.

> Now, IIUC, the new acpi_dev_ready_for_enumeration() is kind of an
> extension of acpi_device_is_present(), so shouldn't it be called by
> acpi_bus_attach() instead of the latter rather than from here?

That is an interesting proposal. I assume you want this to replace
the current acpi_device_is_present() call in acpi_bus_attach()
then ?

For the use-case at hand here that should work fine and it would also
make the honor_deps flag work for devices which bind to the actual
acpi_device (because we delay the device_attach()) or
use an acpi_scan_handler.

This would mean though that we can now have acpi_device-s where
acpi_device_is_present() returns true, but which are not
initialized (do not have device->flags.initialized set)
that would be a new acpi_device state which we have not had
before. I do not immediately forsee this causing issues,
but still...

If you want me to replace the current acpi_device_is_present() call
in acpi_bus_attach() with the new acpi_dev_ready_for_enumeration()
helper, let me know and I'll prepare a new version with this change
(and run some tests with that new version).

Regards,

Hans

>
>> +
>> /*
>> * Do not enumerate devices with enumeration_by_parent flag set as
>> * they will be enumerated by their respective parents.
>> @@ -2313,6 +2328,23 @@ void acpi_dev_clear_dependencies(struct acpi_device *supplier)
>> }
>> EXPORT_SYMBOL_GPL(acpi_dev_clear_dependencies);
>>
>> +/**
>> + * acpi_dev_ready_for_enumeration - Check if the ACPI device is ready for enumeration
>> + * @device: Pointer to the &struct acpi_device to check
>> + *
>> + * Check if the device is present and has no unmet dependencies.
>> + *
>> + * Return true if the device is ready for enumeratino. Otherwise, return false.
>> + */
>> +bool acpi_dev_ready_for_enumeration(const struct acpi_device *device)
>> +{
>> + if (device->flags.honor_deps && device->dep_unmet)
>> + return false;
>> +
>> + return acpi_device_is_present(device);
>> +}
>> +EXPORT_SYMBOL_GPL(acpi_dev_ready_for_enumeration);
>> +
>> /**
>> * acpi_dev_get_first_consumer_dev - Return ACPI device dependent on @supplier
>> * @supplier: Pointer to the dependee device
>> diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
>> index 13d93371790e..2da53b7b4965 100644
>> --- a/include/acpi/acpi_bus.h
>> +++ b/include/acpi/acpi_bus.h
>> @@ -202,7 +202,8 @@ struct acpi_device_flags {
>> u32 coherent_dma:1;
>> u32 cca_seen:1;
>> u32 enumeration_by_parent:1;
>> - u32 reserved:19;
>> + u32 honor_deps:1;
>> + u32 reserved:18;
>> };
>>
>> /* File System */
>> @@ -284,6 +285,7 @@ struct acpi_dep_data {
>> struct list_head node;
>> acpi_handle supplier;
>> acpi_handle consumer;
>> + bool honor_dep;
>> };
>>
>> /* Performance Management */
>> @@ -693,6 +695,7 @@ static inline bool acpi_device_can_poweroff(struct acpi_device *adev)
>> bool acpi_dev_hid_uid_match(struct acpi_device *adev, const char *hid2, const char *uid2);
>>
>> void acpi_dev_clear_dependencies(struct acpi_device *supplier);
>> +bool acpi_dev_ready_for_enumeration(const struct acpi_device *device);
>> struct acpi_device *acpi_dev_get_first_consumer_dev(struct acpi_device *supplier);
>> struct acpi_device *
>> acpi_dev_get_next_match_dev(struct acpi_device *adev, const char *hid, const char *uid, s64 hrv);
>> --
>