| Message ID | 20240117160748.37682-5-brgl@bgdev.pl |
|---|---|
| State | New |
| Headers | show |
| Series | PCI: introduce the concept of power sequencing of PCIe devices | expand |
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@linuxfoundation.org> wrote: > > > > > > On Wed, Jan 17, 2024 at 05:07:43PM +0100, Bartosz Golaszewski wrote: > > > > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org> > > > > > > > > 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? (I'm not questioning the need for having a bus, creating devices, and matching/binding them to a set of drivers) Regards, Bjorn > > Now as for the implementation, the way I see it we have two solutions: > > either we introduce a fake, top-level PCI slot platform device device > > that will reference the PCI host controller by phandle or we will live > > with a secondary, "virtual" platform device for power sequencing that > > is tied to the actual PCI device. The former requires us to add DT > > bindings, add a totally fake DT node representing the "slot" which > > doesn't really exist (and Krzysztof already expressed his negative > > opinion of that) and then have code that will be more complex than it > > needs to be. The latter allows us to not change DT at all (other than > > adding regulators, clocks and GPIOs to already existing WLAN nodes), > > reuse the existing parent-child relationship between the port node and > > the instantiated platform device as well as result in simpler code. > > > > Given that DT needs to be stable while the underlying C code can > > freely change if we find a better solution, I think that the second > > option is a no-brainer here. > > Ok, I remove my objections, sorry about that, my confusion. > > greg k-h
On Tue, Jan 30, 2024 at 10:54 PM Bjorn Andersson <andersson@kernel.org> 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@linuxfoundation.org> wrote: > > > > > > > > On Wed, Jan 17, 2024 at 05:07:43PM +0100, Bartosz Golaszewski wrote: > > > > > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org> > > > > > > > > > > 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. 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". 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]
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@kernel.org> 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@linuxfoundation.org> wrote: > > > > > > > > > > On Wed, Jan 17, 2024 at 05:07:43PM +0100, Bartosz Golaszewski wrote: > > > > > > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org> > > > > > > > > > > > > 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]
On 2/1/2024 4:03 PM, Bjorn Andersson wrote: > 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@kernel.org> 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@linuxfoundation.org> wrote: >>>>>> >>>>>> On Wed, Jan 17, 2024 at 05:07:43PM +0100, Bartosz Golaszewski wrote: >>>>>>> From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org> >>>>>>> >>>>>>> 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. Are you considering out-of-tree drivers? My understanding is that there are different PCIe modules, ones that don't have GPIO-control for x86 and ones that do have GPIO-control for ARM. The out-of-tree cnss platform driver used for Android has a large amount of DT control <https://git.codelinaro.org/clo/la/platform/vendor/qcom-opensource/wlan/platform/-/blob/wlan-platform.lnx.1.0.r1-rel/cnss2/power.c?ref_type=heads> (not sure off hand where the DT files themselves are) /jeff
On Fri, Feb 2, 2024 at 1:03 AM Bjorn Andersson <andersson@kernel.org> 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
On Fri, Feb 2, 2024 at 11:02 AM Bartosz Golaszewski <brgl@bgdev.pl> wrote: > > On Fri, Feb 2, 2024 at 1:03 AM Bjorn Andersson <andersson@kernel.org> 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? > So I was just trying to port this to using the auxiliary bus, only to find myself literally reimplementing functions from drivers/of/device.c. I have a feeling that this is simply wrong. If we're instantiating devices well defined on the device-tree then IMO we *should* make them platform devices. Anything else and we'll be reimplementing drivers/of/ because we will need to parse the device nodes, check the compatible, match it against drivers etc. Things that are already implemented for the platform bus and of_* APIs. Greg: Could you chime in and confirm that it's alright to use the platform bus here? Or maybe there is some infrastructure to create auxiliary devices from software nodes? Bartosz > > 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
On Wed, Feb 07, 2024 at 05:32:38PM +0100, Bartosz Golaszewski wrote: > On Fri, Feb 2, 2024 at 11:02 AM Bartosz Golaszewski <brgl@bgdev.pl> wrote: > > > > On Fri, Feb 2, 2024 at 1:03 AM Bjorn Andersson <andersson@kernel.org> 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? > > > > So I was just trying to port this to using the auxiliary bus, only to > find myself literally reimplementing functions from > drivers/of/device.c. I have a feeling that this is simply wrong. If > we're instantiating devices well defined on the device-tree then IMO > we *should* make them platform devices. Anything else and we'll be > reimplementing drivers/of/ because we will need to parse the device > nodes, check the compatible, match it against drivers etc. Things that > are already implemented for the platform bus and of_* APIs. > > Greg: Could you chime in and confirm that it's alright to use the > platform bus here? Or maybe there is some infrastructure to create > auxiliary devices from software nodes? Note, I HATE the use of the platform bus here, but I don't have a better suggestion. I'd love for the auxbus to work, and if you can create that from software nodes, all the better! But I don't think that's possible just yet, and you would end up implementing all the same stuff that the platform bus has today for this functionality, so I doubt it would be worth it. thanks, greg k-h
diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c index 9c2137dae429..8ab07f711834 100644 --- a/drivers/pci/bus.c +++ b/drivers/pci/bus.c @@ -12,6 +12,7 @@ #include <linux/errno.h> #include <linux/ioport.h> #include <linux/of.h> +#include <linux/of_platform.h> #include <linux/proc_fs.h> #include <linux/slab.h> @@ -342,8 +343,14 @@ void pci_bus_add_device(struct pci_dev *dev) */ pcibios_bus_add_device(dev); pci_fixup_device(pci_fixup_final, dev); - if (pci_is_bridge(dev)) + if (pci_is_bridge(dev)) { of_pci_make_dev_node(dev); + retval = of_platform_populate(dev->dev.of_node, NULL, NULL, + &dev->dev); + if (retval) + pci_err(dev, "failed to populate child OF nodes (%d)\n", + retval); + } pci_create_sysfs_dev_files(dev); pci_proc_attach_device(dev); pci_bridge_d3_update(dev); diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c index d749ea8250d6..77be0630b7b3 100644 --- a/drivers/pci/remove.c +++ b/drivers/pci/remove.c @@ -1,6 +1,7 @@ // SPDX-License-Identifier: GPL-2.0 #include <linux/pci.h> #include <linux/module.h> +#include <linux/of_platform.h> #include "pci.h" static void pci_free_resources(struct pci_dev *dev) @@ -18,11 +19,11 @@ static void pci_stop_dev(struct pci_dev *dev) pci_pme_active(dev, false); if (pci_dev_is_added(dev)) { - device_release_driver(&dev->dev); pci_proc_detach_device(dev); pci_remove_sysfs_dev_files(dev); of_pci_remove_node(dev); + of_platform_depopulate(&dev->dev); pci_dev_assign_added(dev, false); }