| Message ID | 20220701162726.31346-3-jim2101024@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | PCI: brcmstb: Re-submit reverted patchset | expand |
On Fri, Jul 01, 2022 at 12:27:23PM -0400, Jim Quinlan wrote: > Add a mechanism to identify standard PCIe regulators in the DT, allocate > them, and turn them on before the rest of the bus is scanned during > pci_host_probe(). > > The allocated structure that contains the regulators is stored in the port > driver dev.driver_data field. Here is a point-by-point of how and when > this mechanism is activated: > > If: > -- PCIe RC driver sets pci_ops {add,remove)_bus to > pci_subdev_regulators_{add,remove}_bus during its probe. > -- There is a DT node "RB" under the host bridge DT node. "RB" isn't mentioned in pcie-brcmstb.c. What's the connection to it? Is it just an example, and the actual name doesn't matter? > -- During the RC driver's pci_host_probe() the add_bus callback > is invoked where (bus->parent && pci_is_root_bus(bus->parent) > is true > > Then: > -- A struct subdev_regulators structure will be allocated and > assigned to bus->dev.driver_data. > -- regulator_bulk_{get,enable} will be invoked on &bus->dev > and the former will search for and process any > vpcie{12v,3v3,3v3aux}-supply properties that reside in node "RB". > -- The regulators will be turned off/on for any unbind/bind operations. > -- The regulators will be turned off/on for any suspend/resumes, but > only if the RC driver handles this on its own. This will appear > in a later commit for the pcie-brcmstb.c driver. I guess this is all functionality that depends on new properties in the DT? Prior to this patch, pcie-brcmstb.c didn't do anything at all with regulators, although brcm,stb-pcie.yaml does mention "vpcie3v3-supply" in an example. > The unabridged reason for doing this is as follows. We would like the > Broadcom STB PCIe root complex driver (and others) to be able to turn > off/on regulators[1] that provide power to endpoint[2] devices. Typically, > the drivers of these endpoint devices are stock Linux drivers that are not > aware that these regulator(s) exist and must be turned on for the driver to > be probed. The simple solution of course is to turn these regulators on at > boot and keep them on. However, this solution does not satisfy at least > three of our usage modes: > > 1. For example, one customer uses multiple PCIe controllers, but wants > the ability to, by script invoking and unbind, turn any or all of them > and their subdevices off to save power, e.g. when in battery mode. > > 2. Another example is when a watchdog script discovers that an endpoint > device is in an unresponsive state and would like to unbind, power > toggle, and re-bind just the PCIe endpoint and controller. > > 3. Of course we also want power turned off during suspend mode. However, > some endpoint devices may be able to "wake" during suspend and we need > to recognise this case and veto the nominal act of turning off its > regulator. Such is the case with Wake-on-LAN and Wake-on-WLAN support > where the PCIe endpoint device needs to be kept powered on in order to > receive network packets and wake the system. > > In all of these cases it is advantageous for the PCIe controller to govern > the turning off/on the regulators needed by the endpoint device. The first > two cases can be done by simply unbinding and binding the PCIe controller, > if the controller has control of these regulators. > > [1] These regulators typically govern the actual power supply to the > endpoint chip. Sometimes they may be the official PCIe socket > power -- such as 3.3v or aux-3.3v. Sometimes they are truly > the regulator(s) that supply power to the EP chip. > > [2] The 99% configuration of our boards is a single endpoint device > attached to the PCIe controller. I use the term endpoint but it could > possibly mean a switch as well. > > Link: https://lore.kernel.org/r/20220106160332.2143-6-jim2101024@gmail.com > Signed-off-by: Jim Quinlan <jim2101024@gmail.com> > --- > drivers/pci/controller/pcie-brcmstb.c | 77 +++++++++++++++++++++++++++ > 1 file changed, 77 insertions(+) > > diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c > index 2bf5cc399fd0..661d3834c6da 100644 > --- a/drivers/pci/controller/pcie-brcmstb.c > +++ b/drivers/pci/controller/pcie-brcmstb.c > @@ -24,6 +24,7 @@ > #include <linux/pci.h> > #include <linux/pci-ecam.h> > #include <linux/printk.h> > +#include <linux/regulator/consumer.h> > #include <linux/reset.h> > #include <linux/sizes.h> > #include <linux/slab.h> > @@ -283,6 +284,14 @@ static const struct pcie_cfg_data bcm2711_cfg = { > .bridge_sw_init_set = brcm_pcie_bridge_sw_init_set_generic, > }; > > +struct subdev_regulators { > + unsigned int num_supplies; > + struct regulator_bulk_data supplies[]; > +}; > + > +static int pci_subdev_regulators_add_bus(struct pci_bus *bus); > +static void pci_subdev_regulators_remove_bus(struct pci_bus *bus); I think these forward declarations are unnecessary. I can remove them if you agree. > struct brcm_msi { > struct device *dev; > void __iomem *base; > @@ -436,6 +445,72 @@ static int brcm_pcie_set_ssc(struct brcm_pcie *pcie) > return ssc && pll ? 0 : -EIO; > } > > +static void *alloc_subdev_regulators(struct device *dev) > +{ > + static const char * const supplies[] = { > + "vpcie3v3", > + "vpcie3v3aux", > + "vpcie12v", > + }; > + const size_t size = sizeof(struct subdev_regulators) > + + sizeof(struct regulator_bulk_data) * ARRAY_SIZE(supplies); > + struct subdev_regulators *sr; > + int i; > + > + sr = devm_kzalloc(dev, size, GFP_KERNEL); > + if (sr) { > + sr->num_supplies = ARRAY_SIZE(supplies); > + for (i = 0; i < ARRAY_SIZE(supplies); i++) > + sr->supplies[i].supply = supplies[i]; > + } > + > + return sr; > +} > + > +static int pci_subdev_regulators_add_bus(struct pci_bus *bus) > +{ > + struct device *dev = &bus->dev; > + struct subdev_regulators *sr; > + int ret; > + > + if (!dev->of_node || !bus->parent || !pci_is_root_bus(bus->parent)) > + return 0; > + > + if (dev->driver_data) > + dev_err(dev, "dev.driver_data unexpectedly non-NULL\n"); I guess you're using the pci_bus dev->driver_data. I don't know of other users of it, but there's really no ownership model for it. If it's non-NULL here, it means somebody else, e.g., the PCI core, is already using it, and when you overwrite it below, you will break that other user. I think you should complain and return instead of breaking the other user. That will mean the regulator won't get enabled and your endpoint won't work, but I think that's a better way to fail than by overwriting somebody else's pointer, which may lead to memory corruption that's very hard to debug. > + sr = alloc_subdev_regulators(dev); > + if (!sr) > + return -ENOMEM; > + > + dev->driver_data = sr; > + ret = regulator_bulk_get(dev, sr->num_supplies, sr->supplies); > + if (ret) > + return ret; > + > + ret = regulator_bulk_enable(sr->num_supplies, sr->supplies); > + if (ret) { > + dev_err(dev, "failed to enable regulators for downstream device\n"); > + return ret; > + } > + > + return 0; > +} > + > +static void pci_subdev_regulators_remove_bus(struct pci_bus *bus) > +{ > + struct device *dev = &bus->dev; > + struct subdev_regulators *sr = dev->driver_data; > + > + if (!sr || !bus->parent || !pci_is_root_bus(bus->parent)) > + return; > + > + if (regulator_bulk_disable(sr->num_supplies, sr->supplies)) > + dev_err(dev, "failed to disable regulators for downstream device\n"); > + regulator_bulk_free(sr->num_supplies, sr->supplies); > + dev->driver_data = NULL; > +} > + > /* Limits operation to a specific generation (1, 2, or 3) */ > static void brcm_pcie_set_gen(struct brcm_pcie *pcie, int gen) > { > @@ -779,6 +854,8 @@ static struct pci_ops brcm_pcie_ops = { > .map_bus = brcm_pcie_map_conf, > .read = pci_generic_config_read, > .write = pci_generic_config_write, > + .add_bus = pci_subdev_regulators_add_bus, > + .remove_bus = pci_subdev_regulators_remove_bus, > }; > > static struct pci_ops brcm_pcie_ops32 = { > -- > 2.17.1 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On Wed, Jul 6, 2022 at 7:12 PM Bjorn Helgaas <helgaas@kernel.org> wrote: > > On Fri, Jul 01, 2022 at 12:27:23PM -0400, Jim Quinlan wrote: > > Add a mechanism to identify standard PCIe regulators in the DT, allocate > > them, and turn them on before the rest of the bus is scanned during > > pci_host_probe(). > > > > The allocated structure that contains the regulators is stored in the port > > driver dev.driver_data field. Here is a point-by-point of how and when > > this mechanism is activated: > > > > If: > > -- PCIe RC driver sets pci_ops {add,remove)_bus to > > pci_subdev_regulators_{add,remove}_bus during its probe. > > -- There is a DT node "RB" under the host bridge DT node. > > "RB" isn't mentioned in pcie-brcmstb.c. What's the connection to it? > Is it just an example, and the actual name doesn't matter? I will reword this to something like "a regulator with one of these names ... under a root port DT node. I will review/edit this entire commit msg. > > > -- During the RC driver's pci_host_probe() the add_bus callback > > is invoked where (bus->parent && pci_is_root_bus(bus->parent) > > is true > > > > Then: > > -- A struct subdev_regulators structure will be allocated and > > assigned to bus->dev.driver_data. > > -- regulator_bulk_{get,enable} will be invoked on &bus->dev > > and the former will search for and process any > > vpcie{12v,3v3,3v3aux}-supply properties that reside in node "RB". > > -- The regulators will be turned off/on for any unbind/bind operations. > > -- The regulators will be turned off/on for any suspend/resumes, but > > only if the RC driver handles this on its own. This will appear > > in a later commit for the pcie-brcmstb.c driver. > > I guess this is all functionality that depends on new properties in > the DT? Prior to this patch, pcie-brcmstb.c didn't do anything at all > with regulators, although brcm,stb-pcie.yaml does mention > "vpcie3v3-supply" in an example. What is new in the DT is the presence of a regulator under a root port node. That is it. I submitted the regulator YAML allowance to Rob's Github repo and I believe it was accepted. > > > The unabridged reason for doing this is as follows. We would like the > > Broadcom STB PCIe root complex driver (and others) to be able to turn > > off/on regulators[1] that provide power to endpoint[2] devices. Typically, > > the drivers of these endpoint devices are stock Linux drivers that are not > > aware that these regulator(s) exist and must be turned on for the driver to > > be probed. The simple solution of course is to turn these regulators on at > > boot and keep them on. However, this solution does not satisfy at least > > three of our usage modes: > > > > 1. For example, one customer uses multiple PCIe controllers, but wants > > the ability to, by script invoking and unbind, turn any or all of them > > and their subdevices off to save power, e.g. when in battery mode. > > > > 2. Another example is when a watchdog script discovers that an endpoint > > device is in an unresponsive state and would like to unbind, power > > toggle, and re-bind just the PCIe endpoint and controller. > > > > 3. Of course we also want power turned off during suspend mode. However, > > some endpoint devices may be able to "wake" during suspend and we need > > to recognise this case and veto the nominal act of turning off its > > regulator. Such is the case with Wake-on-LAN and Wake-on-WLAN support > > where the PCIe endpoint device needs to be kept powered on in order to > > receive network packets and wake the system. > > > > In all of these cases it is advantageous for the PCIe controller to govern > > the turning off/on the regulators needed by the endpoint device. The first > > two cases can be done by simply unbinding and binding the PCIe controller, > > if the controller has control of these regulators. > > > > [1] These regulators typically govern the actual power supply to the > > endpoint chip. Sometimes they may be the official PCIe socket > > power -- such as 3.3v or aux-3.3v. Sometimes they are truly > > the regulator(s) that supply power to the EP chip. > > > > [2] The 99% configuration of our boards is a single endpoint device > > attached to the PCIe controller. I use the term endpoint but it could > > possibly mean a switch as well. > > > > Link: https://lore.kernel.org/r/20220106160332.2143-6-jim2101024@gmail.com > > Signed-off-by: Jim Quinlan <jim2101024@gmail.com> > > --- > > drivers/pci/controller/pcie-brcmstb.c | 77 +++++++++++++++++++++++++++ > > 1 file changed, 77 insertions(+) > > > > diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c > > index 2bf5cc399fd0..661d3834c6da 100644 > > --- a/drivers/pci/controller/pcie-brcmstb.c > > +++ b/drivers/pci/controller/pcie-brcmstb.c > > @@ -24,6 +24,7 @@ > > #include <linux/pci.h> > > #include <linux/pci-ecam.h> > > #include <linux/printk.h> > > +#include <linux/regulator/consumer.h> > > #include <linux/reset.h> > > #include <linux/sizes.h> > > #include <linux/slab.h> > > @@ -283,6 +284,14 @@ static const struct pcie_cfg_data bcm2711_cfg = { > > .bridge_sw_init_set = brcm_pcie_bridge_sw_init_set_generic, > > }; > > > > +struct subdev_regulators { > > + unsigned int num_supplies; > > + struct regulator_bulk_data supplies[]; > > +}; > > + > > +static int pci_subdev_regulators_add_bus(struct pci_bus *bus); > > +static void pci_subdev_regulators_remove_bus(struct pci_bus *bus); > > I think these forward declarations are unnecessary. I can remove them > if you agree. It is up to you. I have a commit-set ready that will make a number of improvements to our driver. One of them removes all forward declarations. Other commits concern other suggestions you have made, e.g. rename brcm_pcie_linkup() to brcm_pcie_start_link(). > > > struct brcm_msi { > > struct device *dev; > > void __iomem *base; > > @@ -436,6 +445,72 @@ static int brcm_pcie_set_ssc(struct brcm_pcie *pcie) > > return ssc && pll ? 0 : -EIO; > > } > > > > +static void *alloc_subdev_regulators(struct device *dev) > > +{ > > + static const char * const supplies[] = { > > + "vpcie3v3", > > + "vpcie3v3aux", > > + "vpcie12v", > > + }; > > + const size_t size = sizeof(struct subdev_regulators) > > + + sizeof(struct regulator_bulk_data) * ARRAY_SIZE(supplies); > > + struct subdev_regulators *sr; > > + int i; > > + > > + sr = devm_kzalloc(dev, size, GFP_KERNEL); > > + if (sr) { > > + sr->num_supplies = ARRAY_SIZE(supplies); > > + for (i = 0; i < ARRAY_SIZE(supplies); i++) > > + sr->supplies[i].supply = supplies[i]; > > + } > > + > > + return sr; > > +} > > + > > +static int pci_subdev_regulators_add_bus(struct pci_bus *bus) > > +{ > > + struct device *dev = &bus->dev; > > + struct subdev_regulators *sr; > > + int ret; > > + > > + if (!dev->of_node || !bus->parent || !pci_is_root_bus(bus->parent)) > > + return 0; > > + > > + if (dev->driver_data) > > + dev_err(dev, "dev.driver_data unexpectedly non-NULL\n"); > > I guess you're using the pci_bus dev->driver_data. I don't know of > other users of it, but there's really no ownership model for it. If > it's non-NULL here, it means somebody else, e.g., the PCI core, is > already using it, and when you overwrite it below, you will break that > other user. Yes, I'm not happy about this vulnerability. > > I think you should complain and return instead of breaking the other > user. That will mean the regulator won't get enabled and your > endpoint won't work, but I think that's a better way to fail than by > overwriting somebody else's pointer, which may lead to memory > corruption that's very hard to debug. Agree, will do in v2. Regards, Jim Quinlan Broadcom STB > > > + sr = alloc_subdev_regulators(dev); > > + if (!sr) > > + return -ENOMEM; > > + > > + dev->driver_data = sr; > > + ret = regulator_bulk_get(dev, sr->num_supplies, sr->supplies); > > + if (ret) > > + return ret; > > + > > + ret = regulator_bulk_enable(sr->num_supplies, sr->supplies); > > + if (ret) { > > + dev_err(dev, "failed to enable regulators for downstream device\n"); > > + return ret; > > + } > > + > > + return 0; > > +} > > + > > +static void pci_subdev_regulators_remove_bus(struct pci_bus *bus) > > +{ > > + struct device *dev = &bus->dev; > > + struct subdev_regulators *sr = dev->driver_data; > > + > > + if (!sr || !bus->parent || !pci_is_root_bus(bus->parent)) > > + return; > > + > > + if (regulator_bulk_disable(sr->num_supplies, sr->supplies)) > > + dev_err(dev, "failed to disable regulators for downstream device\n"); > > + regulator_bulk_free(sr->num_supplies, sr->supplies); > > + dev->driver_data = NULL; > > +} > > + > > /* Limits operation to a specific generation (1, 2, or 3) */ > > static void brcm_pcie_set_gen(struct brcm_pcie *pcie, int gen) > > { > > @@ -779,6 +854,8 @@ static struct pci_ops brcm_pcie_ops = { > > .map_bus = brcm_pcie_map_conf, > > .read = pci_generic_config_read, > > .write = pci_generic_config_write, > > + .add_bus = pci_subdev_regulators_add_bus, > > + .remove_bus = pci_subdev_regulators_remove_bus, > > }; > > > > static struct pci_ops brcm_pcie_ops32 = { > > -- > > 2.17.1 > > > > > > _______________________________________________ > > linux-arm-kernel mailing list > > linux-arm-kernel@lists.infradead.org > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On Fri, Jul 08, 2022 at 10:14:11AM -0400, Jim Quinlan wrote: > On Wed, Jul 6, 2022 at 7:12 PM Bjorn Helgaas <helgaas@kernel.org> wrote: > > On Fri, Jul 01, 2022 at 12:27:23PM -0400, Jim Quinlan wrote: > > > Add a mechanism to identify standard PCIe regulators in the DT, allocate > > > them, and turn them on before the rest of the bus is scanned during > > > pci_host_probe(). > > > ... > > > +static int pci_subdev_regulators_add_bus(struct pci_bus *bus); > > > +static void pci_subdev_regulators_remove_bus(struct pci_bus *bus); > > > > I think these forward declarations are unnecessary. I can remove them > > if you agree. > > It is up to you. I have a commit-set ready that will make a number of > improvements to our driver. > One of them removes all forward declarations. Other commits concern > other suggestions you > have made, e.g. rename brcm_pcie_linkup() to brcm_pcie_start_link(). If you're planning a v2, I'd drop the declarations there. No point in adding them, only to remove them in a future patch (unless we need them in the interim, of course, but in this case I don't think we do). Bjorn
diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c index 2bf5cc399fd0..661d3834c6da 100644 --- a/drivers/pci/controller/pcie-brcmstb.c +++ b/drivers/pci/controller/pcie-brcmstb.c @@ -24,6 +24,7 @@ #include <linux/pci.h> #include <linux/pci-ecam.h> #include <linux/printk.h> +#include <linux/regulator/consumer.h> #include <linux/reset.h> #include <linux/sizes.h> #include <linux/slab.h> @@ -283,6 +284,14 @@ static const struct pcie_cfg_data bcm2711_cfg = { .bridge_sw_init_set = brcm_pcie_bridge_sw_init_set_generic, }; +struct subdev_regulators { + unsigned int num_supplies; + struct regulator_bulk_data supplies[]; +}; + +static int pci_subdev_regulators_add_bus(struct pci_bus *bus); +static void pci_subdev_regulators_remove_bus(struct pci_bus *bus); + struct brcm_msi { struct device *dev; void __iomem *base; @@ -436,6 +445,72 @@ static int brcm_pcie_set_ssc(struct brcm_pcie *pcie) return ssc && pll ? 0 : -EIO; } +static void *alloc_subdev_regulators(struct device *dev) +{ + static const char * const supplies[] = { + "vpcie3v3", + "vpcie3v3aux", + "vpcie12v", + }; + const size_t size = sizeof(struct subdev_regulators) + + sizeof(struct regulator_bulk_data) * ARRAY_SIZE(supplies); + struct subdev_regulators *sr; + int i; + + sr = devm_kzalloc(dev, size, GFP_KERNEL); + if (sr) { + sr->num_supplies = ARRAY_SIZE(supplies); + for (i = 0; i < ARRAY_SIZE(supplies); i++) + sr->supplies[i].supply = supplies[i]; + } + + return sr; +} + +static int pci_subdev_regulators_add_bus(struct pci_bus *bus) +{ + struct device *dev = &bus->dev; + struct subdev_regulators *sr; + int ret; + + if (!dev->of_node || !bus->parent || !pci_is_root_bus(bus->parent)) + return 0; + + if (dev->driver_data) + dev_err(dev, "dev.driver_data unexpectedly non-NULL\n"); + + sr = alloc_subdev_regulators(dev); + if (!sr) + return -ENOMEM; + + dev->driver_data = sr; + ret = regulator_bulk_get(dev, sr->num_supplies, sr->supplies); + if (ret) + return ret; + + ret = regulator_bulk_enable(sr->num_supplies, sr->supplies); + if (ret) { + dev_err(dev, "failed to enable regulators for downstream device\n"); + return ret; + } + + return 0; +} + +static void pci_subdev_regulators_remove_bus(struct pci_bus *bus) +{ + struct device *dev = &bus->dev; + struct subdev_regulators *sr = dev->driver_data; + + if (!sr || !bus->parent || !pci_is_root_bus(bus->parent)) + return; + + if (regulator_bulk_disable(sr->num_supplies, sr->supplies)) + dev_err(dev, "failed to disable regulators for downstream device\n"); + regulator_bulk_free(sr->num_supplies, sr->supplies); + dev->driver_data = NULL; +} + /* Limits operation to a specific generation (1, 2, or 3) */ static void brcm_pcie_set_gen(struct brcm_pcie *pcie, int gen) { @@ -779,6 +854,8 @@ static struct pci_ops brcm_pcie_ops = { .map_bus = brcm_pcie_map_conf, .read = pci_generic_config_read, .write = pci_generic_config_write, + .add_bus = pci_subdev_regulators_add_bus, + .remove_bus = pci_subdev_regulators_remove_bus, }; static struct pci_ops brcm_pcie_ops32 = {
Add a mechanism to identify standard PCIe regulators in the DT, allocate them, and turn them on before the rest of the bus is scanned during pci_host_probe(). The allocated structure that contains the regulators is stored in the port driver dev.driver_data field. Here is a point-by-point of how and when this mechanism is activated: If: -- PCIe RC driver sets pci_ops {add,remove)_bus to pci_subdev_regulators_{add,remove}_bus during its probe. -- There is a DT node "RB" under the host bridge DT node. -- During the RC driver's pci_host_probe() the add_bus callback is invoked where (bus->parent && pci_is_root_bus(bus->parent) is true Then: -- A struct subdev_regulators structure will be allocated and assigned to bus->dev.driver_data. -- regulator_bulk_{get,enable} will be invoked on &bus->dev and the former will search for and process any vpcie{12v,3v3,3v3aux}-supply properties that reside in node "RB". -- The regulators will be turned off/on for any unbind/bind operations. -- The regulators will be turned off/on for any suspend/resumes, but only if the RC driver handles this on its own. This will appear in a later commit for the pcie-brcmstb.c driver. The unabridged reason for doing this is as follows. We would like the Broadcom STB PCIe root complex driver (and others) to be able to turn off/on regulators[1] that provide power to endpoint[2] devices. Typically, the drivers of these endpoint devices are stock Linux drivers that are not aware that these regulator(s) exist and must be turned on for the driver to be probed. The simple solution of course is to turn these regulators on at boot and keep them on. However, this solution does not satisfy at least three of our usage modes: 1. For example, one customer uses multiple PCIe controllers, but wants the ability to, by script invoking and unbind, turn any or all of them and their subdevices off to save power, e.g. when in battery mode. 2. Another example is when a watchdog script discovers that an endpoint device is in an unresponsive state and would like to unbind, power toggle, and re-bind just the PCIe endpoint and controller. 3. Of course we also want power turned off during suspend mode. However, some endpoint devices may be able to "wake" during suspend and we need to recognise this case and veto the nominal act of turning off its regulator. Such is the case with Wake-on-LAN and Wake-on-WLAN support where the PCIe endpoint device needs to be kept powered on in order to receive network packets and wake the system. In all of these cases it is advantageous for the PCIe controller to govern the turning off/on the regulators needed by the endpoint device. The first two cases can be done by simply unbinding and binding the PCIe controller, if the controller has control of these regulators. [1] These regulators typically govern the actual power supply to the endpoint chip. Sometimes they may be the official PCIe socket power -- such as 3.3v or aux-3.3v. Sometimes they are truly the regulator(s) that supply power to the EP chip. [2] The 99% configuration of our boards is a single endpoint device attached to the PCIe controller. I use the term endpoint but it could possibly mean a switch as well. Link: https://lore.kernel.org/r/20220106160332.2143-6-jim2101024@gmail.com Signed-off-by: Jim Quinlan <jim2101024@gmail.com> --- drivers/pci/controller/pcie-brcmstb.c | 77 +++++++++++++++++++++++++++ 1 file changed, 77 insertions(+)