Re: ACPI: Do not call _STA on battery devices with unmet dependencies

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 19-01-18 22:03, Schmauss, Erik wrote:
> 
>> -----Original Message-----
>> From: linux-acpi-owner@vger.kernel.org [mailto:linux-acpi-
>> owner@vger.kernel.org] On Behalf Of Bjorn Helgaas
>> Sent: Thursday, January 18, 2018 11:11 AM
>> To: Hans de Goede <hdegoede@redhat.com>
>> Cc: Rafael J . Wysocki <rjw@rjwysocki.net>; Len Brown <lenb@kernel.org>;
>> Bjorn Helgaas <bhelgaas@google.com>; Moore, Robert
>> <robert.moore@intel.com>; Zheng, Lv <lv.zheng@intel.com>; linux-
>> acpi@vger.kernel.org; linux-pci@vger.kernel.org; devel@acpica.org
>> Subject: Re: ACPI: Do not call _STA on battery devices with unmet dependencies
>>
>> On Thu, Jan 18, 2018 at 05:03:55PM +0100, Hans de Goede wrote:
> 
> Hi Hans,
> 
>>> Hi All,
>>>
>>> The ACPI code already contains quite a bit of code to not bind the
>>> ACPI-battery until all deps for an ACPI battery device have been met,
>>> but on some devices calling _STA before all deps are met is a problem
>>> too because the _STA method uses an i2c OpRegion there.
> 
> Could you explain why _STA method using an I2C OpRegion is problematic?

It is problematic if we call the _STA method before the handler for
the OpRegion has been installed, this series delays / avoids calling
_STA before the OpRegion has been installed.

Regards,

Hans


> 
> Thanks,
> Erik
> 
>>>
>>> Here is the DSDT of the device I'm seeing this on:
>>> https://fedorapeople.org/~jwrdegoede/toshiba-click-mini-dsdt.dsl
>>
>> This looks like interesting info, but (a) this link isn't mentioned in the actual
>> patches, and (b) it's conceivable that fedorapeople.org could go away someday.
>> If this were a PCI series, I would suggest opening a report at bugzilla.kernel.org,
>> attaching the DSL there, and including the link in the patch changelog.
>>
>>> This series modifies the kernel to not call _STA until all deps are
>>> met, mirroring the binding behavior of the battery driver.
>>>
>>> Without this series a total of 32 ACPI errors get printend to the
>>> console on boot, there are 4 errors per _STA call, 2 battery devices
>>> on this system and 4 _STA calls per battery device.
>>>
>>> The first commit is a preparation commit for making the ACPICA changes
>>> in the 4th commit, this commit is necessary to not break things after
>>> the ACPICA changes.
>>>
>>> The second commit modifies acpi_bus_get_status to not call _STA on
>>> battery devices until all deps are met. This fixes 2 of the 4 too
>>> early _STA calls triggering these errors.
>>>
>>> The third commit makes the device instantiation code use
>>> acpi_bus_get_status instead of acpi_bus_get_status_handle so that the
>>> code to get the initial status also does not makes 1 too early _STA call.
>>>
>>> The fourth commit changes the ACPICA acpi_get_object_info function to
>>> not call _STA. Only 1 user (which is fixed in the first commit) cares
>>> about acpi_device_info.current_status. And the ACPICA code has this
>> comment:
>>>
>>>   * Note: This interface is intended to be used during the initial
>>> device
>>>   * discovery namespace traversal. Therefore, no complex methods can be
>>>   * executed, especially those that access operation regions.
>>> Therefore, do
>>>   * not add any additional methods that could cause problems in this area.
>>>   * Because of this reason support for the following methods has been
>> removed:
>>>   * this was the fate of the _SUB method which was found to cause such
>>>   * problems and was removed (11/2015).
>>>
>>> The described problems with the _SUB method clearly also apply to the
>>> _STA method, so removing it from acpi_get_object_info seems like it is
>>> the right thing to do here. This too fixes 1 too early _STA call, so
>>> that with all
>>> 4 patches in place we've fixed all 4 too early _STA calls.
>>>
>>> Regards,
>>>
>>> Hans
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