Re: efi/reboot: Fall back to original power-off method if EFI_RESET_SHUTDOWN returns

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

Hi,

On 22-06-17 11:55, Matt Fleming wrote:
> On Wed, 21 Jun, at 03:15:09PM, Hans de Goede wrote:
>> HI,
>>
>> On 23-04-17 14:36, Hans de Goede wrote:
>>> Commit 44be28e9dd98 ("x86/reboot: Add EFI reboot quirk for ACPI Hardware
>>> Reduced flag") sets pm_power_off to efi_power_off() when the
>>> acpi_gbl_reduced_hardware flag is set.
>>>
>>> According to its commit message this is necessary because: "BayTrail-T
>>> class of hardware requires EFI in order to powerdown and reboot and no
>>> other reliable method exists"
>>>
>>> But I have a Bay Trail CR tablet where the EFI_RESET_SHUTDOWN call does
>>> not work, it simply returns without doing anything (AFAICT).
>>>
>>> So it seems that some Bay Trail devices must use EFI for power-off, while
>>> for others only ACPI works.
>>>
>>> Note that efi_power_off() only gets used if the platform code defines
>>> efi_poweroff_required() and that returns true, this currently only ever
>>> happens on x86.
>>>
>>> Since on the devices which need ACPI for power-off the EFI_RESET_SHUTDOWN
>>> call simply returns, this patch makes the efi-reboot code remember the
>>> old pm_power_off handler and if EFI_RESET_SHUTDOWN returns it falls back
>>> to calling that.
>>>
>>> This seems preferable to dmi-quirking our way out of this, since there
>>> are likely quite a few devices suffering from this.
>>>
>>> Cc: Mark Salter <msalter@redhat.com>
>>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>>
>> What is the status of this patch ? It has had 2 somewhat favorable
>> reviews and then things went silent ?
> 
> Sorry about the delay. I've picked this up for the efi-next branch
> since we're at -rc6 and it doesn't look like an -rc6-urgent bug.

Ack, putting this in -next is the right thing to do, you never know
what weird firmware quirks this patch may trigger. E.g. EFI_RESET_SHUTDOWN
could return on some models with the PMIC turned off leaving the device
running for XX ms on its power-supply capacitors, and then calling into
the ACPI method may cause weirdness.

Regards,

Hans