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To fix bridge resource allocation issues when powering PCI bridges with the
pwrctrl driver, introduce APIs to explicitly power on and off all related
devices simultaneously.
Previously, the individual pwrctrl drivers powered on/off the PCI devices
autonomously, without any control from the controller drivers. But to
enforce ordering with respect to powering on the devices, these APIs will
power on/off all the devices at the same time.
The pci_pwrctrl_power_on_devices() API recursively scans the PCI child
nodes, makes sure that pwrctrl drivers are bound to devices, and calls
their power_on() callbacks. If any pwrctrl driver is not bound, it will
return -EPROBE_DEFER.
Similarly, pci_pwrctrl_power_off_devices() API powers off devices
recursively via their power_off() callbacks.
These APIs are expected to be called during the controller probe and
suspend/resume time to power on/off the devices. But before calling these
APIs, the pwrctrl devices should be created using the
pci_pwrctrl_{create/destroy}_devices() APIs.
Co-developed-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Link: https://patch.msgid.link/20260115-pci-pwrctrl-rework-v5-11-9d26da3ce903@oss.qualcomm.com
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Previously, the PCI core created pwrctrl devices during pci_scan_device()
on its own and then skipped enumeration of those devices, hoping the
pwrctrl driver would power them on and trigger a bus rescan.
This approach works for endpoint devices directly connected to Root Ports,
but it fails for PCIe switches acting as bus extenders. When the switch
requires pwrctrl support and the pwrctrl driver is not available during
the pwrctrl device creation, its enumeration will be skipped during the
initial PCI bus scan.
This premature scan leads the PCI core to allocate resources (bridge
windows, bus numbers) for the upstream bridge based on available downstream
buses at scan time. For non-hotplug capable bridges, PCI core typically
allocates resources based on the number of buses available during the
initial bus scan, which happens to be just one if the switch is not powered
on and enumerated at that time. When the switch gets enumerated later on,
it will fail due to the lack of upstream resources.
As a result, a PCIe switch powered on by the pwrctrl driver cannot be
reliably enumerated currently. Either the switch has to be enabled in the
bootloader or the switch pwrctrl driver has to be loaded during the pwrctrl
device creation time to work around these issues.
Introduce new APIs to explicitly create and destroy pwrctrl devices from
controller drivers by recursively scanning the PCI child nodes of the
controller. These APIs allow creating pwrctrl devices based on the original
criteria and are intended to be called during controller probe and removal.
These APIs, together with the upcoming APIs for power on/off will allow the
controller drivers to power on all the devices before starting the initial
bus scan, thereby solving the resource allocation issue.
Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
[mani: splitted the patch, cleaned up the code, and rewrote description]
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Link: https://patch.msgid.link/20260115-pci-pwrctrl-rework-v5-10-9d26da3ce903@oss.qualcomm.com
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To allow the pwrctrl core to control the power on/off sequences of the
pwrctrl drivers, add the 'struct pci_pwrctrl::power_{on/off}' callbacks and
populate them in the respective pwrctrl drivers.
The pwrctrl drivers still power on the resources on their own now. So there
is no functional change.
Co-developed-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Link: https://patch.msgid.link/20260115-pci-pwrctrl-rework-v5-9-9d26da3ce903@oss.qualcomm.com
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The correct tag for marking private fields in kerneldoc is "private:", not
capitalized "Private:". Fix the pwrctl struct to silence the following
warnings:
Warning: include/linux/pci-pwrctrl.h:45 struct member 'nb' not described in 'pci_pwrctrl'
Warning: include/linux/pci-pwrctrl.h:45 struct member 'link' not described in 'pci_pwrctrl'
Warning: include/linux/pci-pwrctrl.h:45 struct member 'work' not described in 'pci_pwrctrl'
Fixes: 4565d2652a37 ("PCI/pwrctl: Add PCI power control core code")
Reported-by: Bjorn Helgaas <helgaas@kernel.org>
Closes: https://lore.kernel.org/all/20250617233539.GA1177120@bhelgaas/
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20250618091129.44810-1-brgl@bgdev.pl
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Rename pwrctrl functions and structures from "pwrctl" to "pwrctrl" to match
the similar file renames.
Link: https://lore.kernel.org/r/20241115214428.2061153-3-helgaas@kernel.org
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Acked-by: Krzysztof Wilczyński <kw@linux.com>
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To slightly reduce confusion between "pwrctl" (the power controller and
power sequencing framework) and "bwctrl" (the bandwidth controller),
rename "pwrctl" to "pwrctrl" so they use the same "ctrl" suffix.
Rename drivers/pci/pwrctl/ to drivers/pci/pwrctrl/, including the related
MAINTAINERS, include file (include/linux/pci-pwrctl.h), Makefile, and
Kconfig changes.
This is the minimal rename of files only. A subsequent commit will rename
functions and data structures.
Link: https://lore.kernel.org/r/20241115214428.2061153-2-helgaas@kernel.org
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Acked-by: Krzysztof Wilczyński <kw@linux.com>
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