de116c5fd5
Changes: - SAM: - Add support for Surface Laptop 4 - Fix legacy PIC initialization issue - Add missing device IDs for GPIO controller and UARTs - Small code fixes - Cameras: - Fix for subdevice properties Links: - kernel:0c2ae61563
- SAM:0b52307159
69 lines
2.8 KiB
Diff
69 lines
2.8 KiB
Diff
From 448f0aaa69c07426f1df2ef96075d964545ef1c5 Mon Sep 17 00:00:00 2001
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From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
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Date: Tue, 16 Mar 2021 16:51:40 +0100
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Subject: [PATCH] PCI: PM: Do not read power state in pci_enable_device_flags()
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It should not be necessary to update the current_state field of
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struct pci_dev in pci_enable_device_flags() before calling
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do_pci_enable_device() for the device, because none of the
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code between that point and the pci_set_power_state() call in
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do_pci_enable_device() invoked later depends on it.
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Moreover, doing that is actively harmful in some cases. For example,
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if the given PCI device depends on an ACPI power resource whose _STA
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method initially returns 0 ("off"), but the config space of the PCI
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device is accessible and the power state retrieved from the
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PCI_PM_CTRL register is D0, the current_state field in the struct
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pci_dev representing that device will get out of sync with the
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power.state of its ACPI companion object and that will lead to
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power management issues going forward.
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To avoid such issues it is better to leave the current_state value
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as is until it is changed to PCI_D0 by do_pci_enable_device() as
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appropriate. However, the power state of the device is not changed
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to PCI_D0 if it is already enabled when pci_enable_device_flags()
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gets called for it, so update its current_state in that case, but
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use pci_update_current_state() covering platform PM too for that.
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Link: https://lore.kernel.org/lkml/20210314000439.3138941-1-luzmaximilian@gmail.com/
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Reported-by: Maximilian Luz <luzmaximilian@gmail.com>
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Tested-by: Maximilian Luz <luzmaximilian@gmail.com>
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Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
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Patchset: surface-hotplug
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---
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drivers/pci/pci.c | 16 +++-------------
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1 file changed, 3 insertions(+), 13 deletions(-)
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diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
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index 16a17215f633..e4d4e399004b 100644
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--- a/drivers/pci/pci.c
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+++ b/drivers/pci/pci.c
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@@ -1870,20 +1870,10 @@ static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags)
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int err;
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int i, bars = 0;
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- /*
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- * Power state could be unknown at this point, either due to a fresh
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- * boot or a device removal call. So get the current power state
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- * so that things like MSI message writing will behave as expected
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- * (e.g. if the device really is in D0 at enable time).
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- */
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- if (dev->pm_cap) {
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- u16 pmcsr;
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- pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
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- dev->current_state = (pmcsr & PCI_PM_CTRL_STATE_MASK);
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- }
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-
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- if (atomic_inc_return(&dev->enable_cnt) > 1)
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+ if (atomic_inc_return(&dev->enable_cnt) > 1) {
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+ pci_update_current_state(dev, dev->current_state);
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return 0; /* already enabled */
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+ }
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bridge = pci_upstream_bridge(dev);
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if (bridge)
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--
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2.31.1
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