On Wed, Jan 31, 2024 at 12:04:14PM +0100, Bartosz Golaszewski wrote:

On Tue, Jan 30, 2024 at 10:54 PM Bjorn Andersson [off-list ref] wrote:

quoted

On Thu, Jan 18, 2024 at 12:15:27PM +0100, Greg Kroah-Hartman wrote:

quoted

On Thu, Jan 18, 2024 at 11:58:50AM +0100, Bartosz Golaszewski wrote:

quoted

On Wed, Jan 17, 2024 at 5:45 PM Greg Kroah-Hartman
[off-list ref] wrote:

quoted

On Wed, Jan 17, 2024 at 05:07:43PM +0100, Bartosz Golaszewski wrote:

quoted

From: Bartosz Golaszewski <redacted>

In order to introduce PCI power-sequencing, we need to create platform
devices for child nodes of the port node.

Ick, why a platform device?  What is the parent of this device, a PCI
device?  If so, then this can't be a platform device, as that's not what
it is, it's something else so make it a device of that type,.

Greg,

This is literally what we agreed on at LPC. In fact: during one of the
hall track discussions I said that you typically NAK any attempts at
using the platform bus for "fake" devices but you responded that this
is what the USB on-board HUB does and while it's not pretty, this is
what we need to do.

Ah, you need to remind me of these things, this changelog was pretty
sparse :)

I believe I missed this part of the discussion, why does this need to be
a platform_device? What does the platform_bus bring that can't be
provided by some other bus?

Does it need to be a platform_device? No, of course not. Does it make
sense for it to be one? Yes, for two reasons:

1. The ATH11K WLAN module is represented on the device tree like a
platform device, we know it's always there and it consumes regulators
from another platform device. The fact it uses PCIe doesn't change the
fact that it is logically a platform device.

Are you referring to the ath11k SNOC (firmware running on co-processor
in the SoC) variant?

Afaict the PCIe-attached ath11k is not represented as a platform_device
in DeviceTree.

Said platform_device is also not a child under the PCIe bus, so this
would be a different platform_device...

2. The platform bus already provides us with the entire infrastructure
that we'd now need to duplicate (possibly adding bugs) in order to
introduce a "power sequencing bus".

This is a perfectly reasonable desire. Look at our PMICs, they are full
of platform_devices. But through the years it's been said many times,
that this is not a valid or good reason for using platform_devices, and
as a result we have e.g. auxiliary bus.

Anyway, (please) don't claim that "we need to", when it actually is "we
want to use platform_device because that's more convenient"!

Regards,
Bjorn

Bart

quoted

(I'm not questioning the need for having a bus, creating devices, and
matching/binding them to a set of drivers)

Regards,
Bjorn

[snip]