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drm/xe: Document Xe PM component

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Replace outdated information with a proper PM documentation.
Already establish the rules for the runtime PM get and put that
Xe needs to follow.

Also add missing function documentation to all the "exported" functions.

v2: updated after Francois' feedback.
    s/grater/greater (Matt)
v3: detach D3 from runtime_pm
    remove opportunistic S0iX (Anshuman)

Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Anshuman Gupta <anshuman.gupta@intel.com>
Acked-by: Francois Dugast <francois.dugast@intel.com>
Reviewed-by: Francois Dugast <francois.dugast@intel.com> #v2
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Anshuman Gupta <anshuman.gupta@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240222163937.138342-1-rodrigo.vivi@intel.com
This commit is contained in:
Rodrigo Vivi 2024-02-22 11:39:24 -05:00
parent a9e483dda3
commit 30c399529f
1 changed files with 98 additions and 11 deletions
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109
drivers/gpu/drm/xe/xe_pm.c
View File

@ -25,21 +25,47 @@
/**
* DOC: Xe Power Management
*
* Xe PM shall be guided by the simplicity.
* Use the simplest hook options whenever possible.
* Let's not reinvent the runtime_pm references and hooks.
* Shall have a clear separation of display and gt underneath this component.
* Xe PM implements the main routines for both system level suspend states and
* for the opportunistic runtime suspend states.
*
* What's next:
* 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.
*
* For now s2idle and s3 are only working in integrated devices. The next step
* is to iterate through all VRAM's BO backing them up into the system memory
* before allowing the system suspend.
* 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.
*
* Also runtime_pm needs to be here from the beginning.
* 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.
*
* RC6/RPS are also critical PM features. Let's start with GuCRC and GuC SLPC
* and no wait boost. Frequency optimizations should come on a next stage.
* 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).
*/
/**
@ -178,6 +204,12 @@ void xe_pm_init_early(struct xe_device *xe)
drmm_mutex_init(&xe->drm, &xe->mem_access.vram_userfault.lock);
}
/**
* xe_pm_init - Initialize Xe Power Management
* @xe: xe device instance
*
* This component is responsible for System and Device sleep states.
*/
void xe_pm_init(struct xe_device *xe)
{
/* For now suspend/resume is only allowed with GuC */
@ -196,6 +228,10 @@ void xe_pm_init(struct xe_device *xe)
xe_pm_runtime_init(xe);
}
/**
* xe_pm_runtime_fini - Finalize Runtime PM
* @xe: xe device instance
*/
void xe_pm_runtime_fini(struct xe_device *xe)
{
struct device *dev = xe->drm.dev;
@ -225,6 +261,12 @@ struct task_struct *xe_pm_read_callback_task(struct xe_device *xe)
return READ_ONCE(xe->pm_callback_task);
}
/**
* xe_pm_runtime_suspend - Prepare our device for D3hot/D3Cold
* @xe: xe device instance
*
* Returns 0 for success, negative error code otherwise.
*/
int xe_pm_runtime_suspend(struct xe_device *xe)
{
struct xe_bo *bo, *on;
@ -290,6 +332,12 @@ int xe_pm_runtime_suspend(struct xe_device *xe)
return err;
}
/**
* xe_pm_runtime_resume - Waking up from D3hot/D3Cold
* @xe: xe device instance
*
* Returns 0 for success, negative error code otherwise.
*/
int xe_pm_runtime_resume(struct xe_device *xe)
{
struct xe_gt *gt;
@ -341,22 +389,47 @@ int xe_pm_runtime_resume(struct xe_device *xe)
return err;
}
/**
* xe_pm_runtime_get - Get a runtime_pm reference and resume synchronously
* @xe: xe device instance
*
* Returns: Any number greater than or equal to 0 for success, negative error
* code otherwise.
*/
int xe_pm_runtime_get(struct xe_device *xe)
{
return pm_runtime_get_sync(xe->drm.dev);
}
/**
* xe_pm_runtime_put - Put the runtime_pm reference back and mark as idle
* @xe: xe device instance
*
* Returns: Any number greater than or equal to 0 for success, negative error
* code otherwise.
*/
int xe_pm_runtime_put(struct xe_device *xe)
{
pm_runtime_mark_last_busy(xe->drm.dev);
return pm_runtime_put(xe->drm.dev);
}
/**
* xe_pm_runtime_get_if_active - Get a runtime_pm reference if device active
* @xe: xe device instance
*
* Returns: Any number greater than or equal to 0 for success, negative error
* code otherwise.
*/
int xe_pm_runtime_get_if_active(struct xe_device *xe)
{
return pm_runtime_get_if_active(xe->drm.dev, true);
}
/**
* xe_pm_assert_unbounded_bridge - Disable PM on unbounded pcie parent bridge
* @xe: xe device instance
*/
void xe_pm_assert_unbounded_bridge(struct xe_device *xe)
{
struct pci_dev *pdev = to_pci_dev(xe->drm.dev);
@ -371,6 +444,13 @@ void xe_pm_assert_unbounded_bridge(struct xe_device *xe)
}
}
/**
* xe_pm_set_vram_threshold - Set a vram threshold for allowing/blocking D3Cold
* @xe: xe device instance
* @threshold: VRAM size in bites for the D3cold threshold
*
* Returns 0 for success, negative error code otherwise.
*/
int xe_pm_set_vram_threshold(struct xe_device *xe, u32 threshold)
{
struct ttm_resource_manager *man;
@ -395,6 +475,13 @@ int xe_pm_set_vram_threshold(struct xe_device *xe, u32 threshold)
return 0;
}
/**
* xe_pm_d3cold_allowed_toggle - Check conditions to toggle d3cold.allowed
* @xe: xe device instance
*
* To be called during runtime_pm idle callback.
* Check for all the D3Cold conditions ahead of runtime suspend.
*/
void xe_pm_d3cold_allowed_toggle(struct xe_device *xe)
{
struct ttm_resource_manager *man;