[PATCH 5.8+ regression fix 0/1] i2c: core: Restore acpi_walk_dep_device_list() getting called after registering the ACPI i2c devs

[PATCH 5.8+ regression fix 0/1] i2c: core: Restore acpi_walk_dep_device_list() getting called after registering the ACPI i2c devs

[Hans de Goede]

Hi All,

I am afraid that commit 21653a4181ff ("i2c: core: Call
i2c_acpi_install_space_handler() before i2c_acpi_register_devices()")
which is in 5.9 and was also added to 5.8.13 (and possible other
stable series releases) causes a regression on some devices including
on the Microsoft Surface Go 2 (and possibly also the Go 1) where the
system no longer boots.

Before the troublesome commit the ACPI related i2c core code looked
like this:

        /* create pre-declared device nodes */
        of_i2c_register_devices(adap);
        i2c_acpi_register_devices(adap);
        i2c_acpi_install_space_handler(adap);

	if (...

The trouble some commit changed this to:

        /* create pre-declared device nodes */
        of_i2c_register_devices(adap);
        i2c_acpi_install_space_handler(adap);
        i2c_acpi_register_devices(adap);

	if (...

The goal here was to only move the acpi_install_address_space_handler()
which is wrapped by i2c_acpi_install_space_handler() which should be
pretty safe. But as Maximilian Luz' sharp eyes pointed out while
debugging the regression, i2c_acpi_install_space_handler() does more,
it also contains a call to acpi_walk_dep_device_list() at the end.
Which I missed and which is causing the trouble we are seeing now.

The original code flow looked like this:

1.  i2c_acpi_register_devices()
1.1  Create ACPI declared i2c_clients for adap
2.  i2c_acpi_install_space_handler(adap);
2.1  acpi_install_address_space_handler()
2.2  acpi_walk_dep_device_list()

And after the troublesome commit it now looks like this:

1.  i2c_acpi_install_space_handler(adap);
1.1  acpi_install_address_space_handler()
1.2  acpi_walk_dep_device_list()
2.  i2c_acpi_register_devices()
2.1  Create ACPI declared i2c_clients for adap

Notice that the acpi_walk_dep_device_list() now happens before
the i2c_clients below this adapter are created.

The patch in this 1 patch series fixes this by moving the
acpi_walk_dep_device_list() call to the end of
i2c_acpi_register_devices(), partly restoring the original
order, so that we now get:

1.  i2c_acpi_install_space_handler(adap);
1.1  acpi_install_address_space_handler()
2.  i2c_acpi_register_devices()
2.1  Create ACPI declared i2c_clients for adap
2.2  acpi_walk_dep_device_list()

So we end up calling acpi_walk_dep_device_list() last
again, as before.

Sorry for missing this the first time around.

Wolfram, can we get this queued up to go to Linus
soonish ?

Greg, in essence this is a partial revert of the trouble
some commit. With the 2 combined acpi_walk_dep_device_list()
is called last again, while still doing the
acpi_install_address_space_handler() call earlier.

Since this is a somewhat nasty regression and since the poor
timing wrt the merge-window, I was hoping that you would be
willing to make an exception and pick up this fix before
it hits Linus' tree?

The alternative would be to revert this now and then pick
up both again later, when the fix has landed in Linus'
tree. The problem with that is that reverting the original
troublesome commit will regress all these bugs:

https://bugzilla.redhat.com/show_bug.cgi?id=1842039
https://bugzilla.redhat.com/show_bug.cgi?id=1871793
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1861610

Regards,

Hans

[PATCH 5.8+ regression fix] i2c: core: Restore acpi_walk_dep_device_list() getting called after registering the ACPI i2c devs

[Hans de Goede]

Commit 21653a4181ff ("i2c: core: Call i2c_acpi_install_space_handler()
before i2c_acpi_register_devices()")'s intention was to only move the
acpi_install_address_space_handler() call to the point before where
the ACPI declared i2c-children of the adapter where instantiated by
i2c_acpi_register_devices().

But i2c_acpi_install_space_handler() had a call to
acpi_walk_dep_device_list() hidden (that is I missed it) at the end
of it, so as an unwanted side-effect now acpi_walk_dep_device_list()
was also being called before i2c_acpi_register_devices().

Move the acpi_walk_dep_device_list() call to the end of
i2c_acpi_register_devices(), so that it is once again called *after*
the i2c_client-s hanging of the adapter have been created.

This fixes the Microsoft Surface Go 2 hanging at boot.

Fixes: 21653a4181ff ("i2c: core: Call i2c_acpi_install_space_handler() before i2c_acpi_register_devices()")
Suggested-by: Maximilian Luz <luzmaximilian@gmail.com>
Reported-and-tested-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/i2c/i2c-core-acpi.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/i2c-core-acpi.c b/drivers/i2c/i2c-core-acpi.c
index e627d7b2790f..37c510d9347a 100644
--- a/drivers/i2c/i2c-core-acpi.c
+++ b/drivers/i2c/i2c-core-acpi.c
@@ -264,6 +264,7 @@ static acpi_status i2c_acpi_add_device(acpi_handle handle, u32 level,
 void i2c_acpi_register_devices(struct i2c_adapter *adap)
 {
 	acpi_status status;
+	acpi_handle handle;
 
 	if (!has_acpi_companion(&adap->dev))
 		return;
@@ -274,6 +275,15 @@ void i2c_acpi_register_devices(struct i2c_adapter *adap)
 				     adap, NULL);
 	if (ACPI_FAILURE(status))
 		dev_warn(&adap->dev, "failed to enumerate I2C slaves\n");
+
+	if (!adap->dev.parent)
+		return;
+
+	handle = ACPI_HANDLE(adap->dev.parent);
+	if (!handle)
+		return;
+
+	acpi_walk_dep_device_list(handle);
 }
 
 static const struct acpi_device_id i2c_acpi_force_400khz_device_ids[] = {
@@ -719,7 +729,6 @@ int i2c_acpi_install_space_handler(struct i2c_adapter *adapter)
 		return -ENOMEM;
 	}
 
-	acpi_walk_dep_device_list(handle);
 	return 0;
 }
 
-- 
2.28.0

Re: [PATCH 5.8+ regression fix] i2c: core: Restore acpi_walk_dep_device_list() getting called after registering the ACPI i2c devs

[Wolfram Sang]

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On Wed, Oct 14, 2020 at 04:41:58PM +0200, Hans de Goede wrote:
> Commit 21653a4181ff ("i2c: core: Call i2c_acpi_install_space_handler()
> before i2c_acpi_register_devices()")'s intention was to only move the
> acpi_install_address_space_handler() call to the point before where
> the ACPI declared i2c-children of the adapter where instantiated by
> i2c_acpi_register_devices().
> 
> But i2c_acpi_install_space_handler() had a call to
> acpi_walk_dep_device_list() hidden (that is I missed it) at the end
> of it, so as an unwanted side-effect now acpi_walk_dep_device_list()
> was also being called before i2c_acpi_register_devices().
> 
> Move the acpi_walk_dep_device_list() call to the end of
> i2c_acpi_register_devices(), so that it is once again called *after*
> the i2c_client-s hanging of the adapter have been created.
> 
> This fixes the Microsoft Surface Go 2 hanging at boot.
> 
> Fixes: 21653a4181ff ("i2c: core: Call i2c_acpi_install_space_handler() before i2c_acpi_register_devices()")
> Suggested-by: Maximilian Luz <luzmaximilian@gmail.com>
> Reported-and-tested-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Applied to for-current, thanks!


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Re: [PATCH 5.8+ regression fix 0/1] i2c: core: Restore acpi_walk_dep_device_list() getting called after registering the ACPI i2c devs

[Greg Kroah-Hartman]

On Wed, Oct 14, 2020 at 04:41:57PM +0200, Hans de Goede wrote:
> Hi All,
> 
> I am afraid that commit 21653a4181ff ("i2c: core: Call
> i2c_acpi_install_space_handler() before i2c_acpi_register_devices()")
> which is in 5.9 and was also added to 5.8.13 (and possible other
> stable series releases) causes a regression on some devices including
> on the Microsoft Surface Go 2 (and possibly also the Go 1) where the
> system no longer boots.

That commit is also in the following stable releases:
	4.9.238 4.14.200 4.19.149 5.4.69 5.8.13

so it would need to fixed in all of those places :)

thanks,

greg k-h

Re: [PATCH 5.8+ regression fix 0/1] i2c: core: Restore acpi_walk_dep_device_list() getting called after registering the ACPI i2c devs

[Sasha Levin]

On Wed, Oct 14, 2020 at 04:41:57PM +0200, Hans de Goede wrote:
>Wolfram, can we get this queued up to go to Linus
>soonish ?
>
>Greg, in essence this is a partial revert of the trouble
>some commit. With the 2 combined acpi_walk_dep_device_list()
>is called last again, while still doing the
>acpi_install_address_space_handler() call earlier.
>
>Since this is a somewhat nasty regression and since the poor
>timing wrt the merge-window, I was hoping that you would be
>willing to make an exception and pick up this fix before
>it hits Linus' tree?

I don't think the merge window plays any role here: this fix can go into
Linus's tree immediately and once it's there we can pick it up for
-stable right away.

-- 
Thanks,
Sasha