On Thursday, June 22, 2017 11:35:35 AM Ulf Hansson wrote:

On 21 June 2017 at 23:42, Rafael J. Wysocki [off-list ref] wrote:

quoted

On Wed, Jun 21, 2017 at 9:21 PM, Ulf Hansson [off-list ref] wrote:

quoted

In some cases a driver for an ACPI device needs to be able to prevent the
ACPI PM domain from using the direct_complete path during system sleep.

One typical case is when the driver for the device needs its device to stay
runtime enabled, during the __device_suspend phase. This isn't the case
when the direct_complete path is being executed by the PM core, as it then
disables runtime PM for the device in __device_suspend(). Any following
attempts to runtime resume the device after that point, just fails.

A workaround to this problem is to let the driver runtime resume its device
from its ->prepare() callback, as that would prevent the direct_complete
path from being executed. However, that may often be a waste, especially if
it turned out that no one really needed the device.

For this reason, invent acpi_dev_disable|enable_direct_complete(), to allow
drivers to inform the ACPI PM domain to change its default behaviour during
system sleep, and thus control whether it may use the direct_complete path
or not.

Typically a driver should call acpi_dev_disable_direct_comlete() during
->probe() and acpi_dev_enable_direct_complete() in ->remove().

Signed-off-by: Ulf Hansson <redacted>
---
 drivers/acpi/device_pm.c | 37 ++++++++++++++++++++++++++++++++++++-
 include/acpi/acpi_bus.h  |  1 +
 include/linux/acpi.h     |  4 ++++
 3 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/device_pm.c b/drivers/acpi/device_pm.c
index ee51e75..2393a1a 100644
--- a/drivers/acpi/device_pm.c
+++ b/drivers/acpi/device_pm.c

@@ -879,6 +879,41 @@ EXPORT_SYMBOL_GPL(acpi_subsys_runtime_resume);

 #ifdef CONFIG_PM_SLEEP
 /**
+ * acpi_dev_disable_direct_complete - Disable the direct_complete path for ACPI.
+ * @dev: Device to disable the path for.
+ *
+ * Per default the ACPI PM domain tries to use the direct_complete path for its
+ * devices during system sleep. This function allows a user, typically a driver
+ * during probe, to disable the direct_complete path from being used by ACPI.
+ */
+void acpi_dev_disable_direct_complete(struct device *dev)
+{
+       struct acpi_device *adev = ACPI_COMPANION(dev);
+
+       if (adev)
+               adev->no_direct_complete = true;

We have an analogous flag in PCI now and it is called needs_resume, so
it would be good to be consistent with that.

I was trying to come up with a nice name, however I couldn't find
anything better than no_direct_complete.

However as the next patch somewhat, extends the flag to also be use
for the runtime PM centric path, I should perhaps choose something
more related to that?

I think make "needs_resume" is going to e bit confusing, especially
while extending the usage for the flag it in the next patch, no?

OK, fair enough, but I still think the name isn't really nice. :-)

In fact, I'm not sure if the new flag is necessary at all.

If the driver is expected to use pm_runtime_force_suspend|resume() along with
it every time, why not to make the ACPI PM domain code check if the driver's
callback pointers point to pm_runtime_force_suspend|resume() and work
accordingly?

Thanks,
Rafael