Runtime Power Management¶
Xe PM implements the main routines for both system level suspend states and for the opportunistic runtime suspend states.
System Level Suspend (S-States) - In general this is OS initiated suspend driven by ACPI for achieving S0ix (a.k.a. S2idle, freeze), S3 (suspend to ram), S4 (disk). The main functions here are xe_pm_suspend and xe_pm_resume. They are the main point for the suspend to and resume from these states.
PCI Device Suspend (D-States) - This is the opportunistic PCIe device low power state D3, controlled by the PCI subsystem and ACPI with the help from the runtime_pm infrastructure. PCI D3 is special and can mean D3hot, where Vcc power is on for keeping memory alive and quicker low latency resume or D3Cold where Vcc power is off for better power savings. The Vcc control of PCI hierarchy can only be controlled at the PCI root port level, while the device driver can be behind multiple bridges/switches and paired with other devices. For this reason, the PCI subsystem cannot perform the transition towards D3Cold. The lowest runtime PM possible from the PCI subsystem is D3hot. Then, if all these paired devices in the same root port are in D3hot, ACPI will assist here and run its own methods (_PR3 and _OFF) to perform the transition from D3hot to D3cold. Xe may disallow this transition by calling pci_d3cold_disable(root_pdev) before going to runtime suspend. It will be based on runtime conditions such as VRAM usage for a quick and low latency resume for instance.
Runtime PM - This infrastructure provided by the Linux kernel allows the device drivers to indicate when the can be runtime suspended, so the device could be put at D3 (if supported), or allow deeper package sleep states (PC-states), and/or other low level power states. Xe PM component provides xe_pm_runtime_suspend and xe_pm_runtime_resume functions that PCI subsystem will call before transition to/from runtime suspend.
Also, Xe PM provides get and put functions that Xe driver will use to indicate activity. In order to avoid locking complications with the memory management, whenever possible, these get and put functions needs to be called from the higher/outer levels. The main cases that need to be protected from the outer levels are: IOCTL, sysfs, debugfs, dma-buf sharing, GPU execution.
This component is not responsible for GT idleness (RC6) nor GT frequency management (RPS).
Internal API¶
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int xe_pm_suspend(struct xe_device *xe)¶
Helper for System suspend, i.e. S0->S3 / S0->S2idle
Parameters
struct xe_device *xexe device instance
Return
0 on success
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int xe_pm_resume(struct xe_device *xe)¶
Helper for System resume S3->S0 / S2idle->S0
Parameters
struct xe_device *xexe device instance
Return
0 on success
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int xe_pm_init(struct xe_device *xe)¶
Initialize Xe Power Management
Parameters
struct xe_device *xexe device instance
Description
This component is responsible for System and Device sleep states.
Returns 0 for success, negative error code otherwise.
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void xe_pm_runtime_fini(struct xe_device *xe)¶
Finalize Runtime PM
Parameters
struct xe_device *xexe device instance
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bool xe_pm_runtime_suspended(struct xe_device *xe)¶
Check if runtime_pm state is suspended
Parameters
struct xe_device *xexe device instance
Description
This does not provide any guarantee that the device is going to remain suspended as it might be racing with the runtime state transitions. It can be used only as a non-reliable assertion, to ensure that we are not in the sleep state while trying to access some memory for instance.
Returns true if PCI device is suspended, false otherwise.
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int xe_pm_runtime_suspend(struct xe_device *xe)¶
Prepare our device for D3hot/D3Cold
Parameters
struct xe_device *xexe device instance
Description
Returns 0 for success, negative error code otherwise.
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int xe_pm_runtime_resume(struct xe_device *xe)¶
Waking up from D3hot/D3Cold
Parameters
struct xe_device *xexe device instance
Description
Returns 0 for success, negative error code otherwise.
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void xe_pm_runtime_get(struct xe_device *xe)¶
Get a runtime_pm reference and resume synchronously
Parameters
struct xe_device *xexe device instance
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void xe_pm_runtime_put(struct xe_device *xe)¶
Put the runtime_pm reference back and mark as idle
Parameters
struct xe_device *xexe device instance
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int xe_pm_runtime_get_ioctl(struct xe_device *xe)¶
Get a runtime_pm reference before ioctl
Parameters
struct xe_device *xexe device instance
Return
Any number greater than or equal to 0 for success, negative error code otherwise.
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bool xe_pm_runtime_get_if_active(struct xe_device *xe)¶
Get a runtime_pm reference if device active
Parameters
struct xe_device *xexe device instance
Return
True if device is awake (regardless the previous number of references) and a new reference was taken, false otherwise.
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bool xe_pm_runtime_get_if_in_use(struct xe_device *xe)¶
Get a new reference if device is active with previous ref taken
Parameters
struct xe_device *xexe device instance
Return
True if device is awake, a previous reference had been already taken, and a new reference was now taken, false otherwise.
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void xe_pm_runtime_get_noresume(struct xe_device *xe)¶
Bump runtime PM usage counter without resuming
Parameters
struct xe_device *xexe device instance
Description
This function should be used in inner places where it is surely already protected by outer-bound callers of xe_pm_runtime_get. It will warn if not protected. The reference should be put back after this function regardless, since it will always bump the usage counter, regardless.
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bool xe_pm_runtime_resume_and_get(struct xe_device *xe)¶
Resume, then get a runtime_pm ref if awake.
Parameters
struct xe_device *xexe device instance
Return
True if device is awake and the reference was taken, false otherwise.
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void xe_pm_assert_unbounded_bridge(struct xe_device *xe)¶
Disable PM on unbounded pcie parent bridge
Parameters
struct xe_device *xexe device instance
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int xe_pm_set_vram_threshold(struct xe_device *xe, u32 threshold)¶
Set a vram threshold for allowing/blocking D3Cold
Parameters
struct xe_device *xexe device instance
u32 thresholdVRAM size in bites for the D3cold threshold
Description
Returns 0 for success, negative error code otherwise.
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void xe_pm_d3cold_allowed_toggle(struct xe_device *xe)¶
Check conditions to toggle d3cold.allowed
Parameters
struct xe_device *xexe device instance
Description
To be called during runtime_pm idle callback. Check for all the D3Cold conditions ahead of runtime suspend.