On Wednesday, October 25, 2023 4:05:43 AM CEST Mario Limonciello wrote:
> Before kernel 3.6 D3cold was considered "opt-in" for PCIe devices.
> Userspace was able to opt PCIe devices into d3cold support by using
> the `d3cold_allowed` sysfs attribute. The policy changed to default
> to enabled with commit 4f9c1397e2e8 ("PCI/PM: Enable D3/D3cold by
> default for most devices"). The sysfs file remains however and
> can potentially allow userspace to prevent the SoC from getting into
> the deepest sleep state on modern systems.
>
> For debugging purposes `pcie_port_pm=` can be used to control whether
> a PCI port will go into D3cold and runtime PM can be turned off by
> `/sys/bus/pci/devices/*/power/control` on PCI end points.
>
> Change the sysfs attribute to a noop that ignores the input when written
> and shows a warning. Simplify the internal kernel logic to drop
> `d3cold_allowed`.
>
> Link: https://lore.kernel.org/linux-pci/20230918132424.GA11357@xxxxxxxxx/
> Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
I'm not aware of anyone using this sysfs i/f in practice, so
Acked-by: Rafael J. Wysocki <rafael@xxxxxxxxxx>
> ---
> Changes from previous submission:
> * Update commit message
> * Roll into series for D3 related handling
> ---
> Documentation/ABI/testing/sysfs-bus-pci | 4 ++--
> drivers/pci/pci-acpi.c | 2 +-
> drivers/pci/pci-sysfs.c | 14 ++------------
> drivers/pci/pci.c | 3 +--
> include/linux/pci.h | 1 -
> 5 files changed, 6 insertions(+), 18 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
> index ecf47559f495..b5db141dfee6 100644
> --- a/Documentation/ABI/testing/sysfs-bus-pci
> +++ b/Documentation/ABI/testing/sysfs-bus-pci
> @@ -283,8 +283,8 @@ Description:
> device will never be put into D3Cold state. If it is set, the
> device may be put into D3Cold state if other requirements are
> satisfied too. Reading this attribute will show the current
> - value of d3cold_allowed bit. Writing this attribute will set
> - the value of d3cold_allowed bit.
> + value of no_d3cold bit.
> + Writing to this attribute is deprecated and will do nothing.
>
> What: /sys/bus/pci/devices/.../sriov_totalvfs
> Date: November 2012
> diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
> index 05b7357bd258..a05350a4e49c 100644
> --- a/drivers/pci/pci-acpi.c
> +++ b/drivers/pci/pci-acpi.c
> @@ -911,7 +911,7 @@ pci_power_t acpi_pci_choose_state(struct pci_dev *pdev)
> {
> int acpi_state, d_max;
>
> - if (pdev->no_d3cold || !pdev->d3cold_allowed)
> + if (pdev->no_d3cold)
> d_max = ACPI_STATE_D3_HOT;
> else
> d_max = ACPI_STATE_D3_COLD;
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index 5e741a05cf2c..52ed5a55a371 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -523,17 +523,7 @@ static ssize_t d3cold_allowed_store(struct device *dev,
> struct device_attribute *attr,
> const char *buf, size_t count)
> {
> - struct pci_dev *pdev = to_pci_dev(dev);
> - unsigned long val;
> -
> - if (kstrtoul(buf, 0, &val) < 0)
> - return -EINVAL;
> -
> - pdev->d3cold_allowed = !!val;
> - pci_bridge_d3_update(pdev);
> -
> - pm_runtime_resume(dev);
> -
> + dev_warn_once(dev, "pci: writing to d3cold_allowed is deprecated\n");
> return count;
> }
>
> @@ -541,7 +531,7 @@ static ssize_t d3cold_allowed_show(struct device *dev,
> struct device_attribute *attr, char *buf)
> {
> struct pci_dev *pdev = to_pci_dev(dev);
> - return sysfs_emit(buf, "%u\n", pdev->d3cold_allowed);
> + return sysfs_emit(buf, "%u\n", !pdev->no_d3cold);
> }
> static DEVICE_ATTR_RW(d3cold_allowed);
> #endif
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 59c01d68c6d5..8c5a6f68f63d 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -3067,7 +3067,7 @@ static int pci_dev_check_d3cold(struct pci_dev *dev, void *data)
> bool *d3cold_ok = data;
>
> if (/* The device needs to be allowed to go D3cold ... */
> - dev->no_d3cold || !dev->d3cold_allowed ||
> + dev->no_d3cold ||
>
> /* ... and if it is wakeup capable to do so from D3cold. */
> (device_may_wakeup(&dev->dev) &&
> @@ -3204,7 +3204,6 @@ void pci_pm_init(struct pci_dev *dev)
> dev->d3hot_delay = PCI_PM_D3HOT_WAIT;
> dev->d3cold_delay = PCI_PM_D3COLD_WAIT;
> dev->bridge_d3 = pci_bridge_d3_possible(dev);
> - dev->d3cold_allowed = true;
>
> dev->d1_support = false;
> dev->d2_support = false;
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 8c7c2c3c6c65..5f4ed71d31f5 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -376,7 +376,6 @@ struct pci_dev {
> unsigned int no_d1d2:1; /* D1 and D2 are forbidden */
> unsigned int no_d3cold:1; /* D3cold is forbidden */
> unsigned int bridge_d3:1; /* Allow D3 for bridge */
> - unsigned int d3cold_allowed:1; /* D3cold is allowed by user */
> unsigned int mmio_always_on:1; /* Disallow turning off io/mem
> decoding during BAR sizing */
> unsigned int wakeup_prepared:1;
>
