On Fri, Feb 2, 2024 at 1:03 AM Bjorn Andersson <andersson@xxxxxxxxxx> wrote: > [snip] > > > > > > 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. > My bad. In RB5 it isn't (yet - I want to add it in the power sequencing series). It is in X13s though[1]. > Said platform_device is also not a child under the PCIe bus, so this > would be a different platform_device... > It's the child of the PCIe port node but there's a reason for it to have the `compatible` property. It's because it's an entity of whose existence we are aware before the system boots. > > 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. > Ok, so I cannot find this information anywhere (nor any example). Do you happen to know if the auxiliary bus offers any software node integration so that the `compatible` property from DT can get seamlessly mapped to auxiliary device IDs? > Anyway, (please) don't claim that "we need to", when it actually is "we > want to use platform_device because that's more convenient"! Bart [snip] [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts#n744
