On Wed, Jan 31, 2024 at 12:04:14PM +0100, Bartosz Golaszewski wrote: > On Tue, Jan 30, 2024 at 10:54 PM Bjorn Andersson <andersson@xxxxxxxxxx> wrote: > > > > On Thu, Jan 18, 2024 at 12:15:27PM +0100, Greg Kroah-Hartman wrote: > > > On Thu, Jan 18, 2024 at 11:58:50AM +0100, Bartosz Golaszewski wrote: > > > > On Wed, Jan 17, 2024 at 5:45 PM Greg Kroah-Hartman > > > > <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > > > > > > On Wed, Jan 17, 2024 at 05:07:43PM +0100, Bartosz Golaszewski wrote: > > > > > > From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx> > > > > > > > > > > > > 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 > > > (I'm not questioning the need for having a bus, creating devices, and > > matching/binding them to a set of drivers) > > > > Regards, > > Bjorn > > > > [snip]
