[RFC 1/2] drm/xe: Introduce PM guard classes

[Lucas De Marchi]

On Mon, Jun 17, 2024 at 04:01:19PM GMT, Michal Wajdeczko wrote:
>There is support for 'classes' with constructor and destructor
>semantics that can be used for scope-based resource management,
>like our device power management.
>
>Use provided macros from linux/cleanup.h to generate required
>code definitions.
>
>This should allow us to use:
>
>	scoped_guard(xe_pm, xe)
>		foo();
>or
>	CLASS(xe_pm, var)(xe);
>
>without any concern of leaking the pm reference.
>
>Signed-off-by: Michal Wajdeczko <michal.wajdeczko at intel.com>
>Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
>Cc: Lucas De Marchi <lucas.demarchi at intel.com>
>---
> drivers/gpu/drm/xe/xe_pm.h | 5 +++++
> 1 file changed, 5 insertions(+)
>
>diff --git a/drivers/gpu/drm/xe/xe_pm.h b/drivers/gpu/drm/xe/xe_pm.h
>index 104a21ae6dfd..26293a3b18af 100644
>--- a/drivers/gpu/drm/xe/xe_pm.h
>+++ b/drivers/gpu/drm/xe/xe_pm.h
>@@ -6,6 +6,7 @@
> #ifndef _XE_PM_H_
> #define _XE_PM_H_
>
>+#include <linux/cleanup.h>

Cool, I didn't know we had  helpers in the kernel for attribute cleanup
and friends.

> #include <linux/pm_runtime.h>
>
> #define DEFAULT_VRAM_THRESHOLD 300 /* in MB */
>@@ -33,4 +34,8 @@ int xe_pm_set_vram_threshold(struct xe_device *xe, u32 threshold);
> void xe_pm_d3cold_allowed_toggle(struct xe_device *xe);
> struct task_struct *xe_pm_read_callback_task(struct xe_device *xe);
>
>+DEFINE_GUARD(xe_pm, struct xe_device *, xe_pm_runtime_get(_T), xe_pm_runtime_put(_T))

per linux/cleanup.h doc it seems DEFINE_GUARD() was intended
specifically for locks though:

  * DEFINE_GUARD(name, type, lock, unlock):
  *      trivial wrapper around DEFINE_CLASS() above specifically
  *      for locks.

we probably shouldn't abuse it or get the doc changed

Lucas De Marchi

>+DEFINE_GUARD_COND(xe_pm, _if_active, xe_pm_runtime_get_if_active(_T))
>+DEFINE_GUARD_COND(xe_pm, _if_in_use, xe_pm_runtime_get_if_in_use(_T))
>+
> #endif
>-- 
>2.43.0
>