[PATCH AUTOSEL 6.17] drm/xe: Ensure GT is in C0 during resumes

[Sasha Levin <sashal@kernel.org>]

From: Xin Wang <x.wang@intel.com>

[ Upstream commit 95d0883ac8105717f59c2dcdc0d8b9150f13aa12 ]

This patch ensures the gt will be awake for the entire duration
of the resume sequences until GuCRC takes over and GT-C6 gets
re-enabled.

Before suspending GT-C6 is kept enabled, but upon resume, GuCRC
is not yet alive to properly control the exits and some cases of
instability and corruption related to GT-C6 can be observed.

Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/4037

Suggested-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Xin Wang <x.wang@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/4037
Link: https://lore.kernel.org/r/20250827000633.1369890-3-x.wang@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

LLM Generated explanations, may be completely bogus:

YES

- Fixes real user-visible bugs: The commit addresses resume-time
  instability and corruption linked to GT-C6 being enabled before GuC
  (power control) is up, as described in the message and tracked by the
  referenced issue. Keeping the GT awake through resume avoids those
  failures.

- Small, contained change: It only adds early RC6 disable during resume
  paths and the required header:
  - Adds `#include "xe_gt_idle.h"` so the helper is visible
    (drivers/gpu/drm/xe/xe_pm.c:21).
  - System resume: disables GT-C6 for all GTs right at resume entry,
    before any other resume work (drivers/gpu/drm/xe/xe_pm.c:184-186).
  - Runtime resume: same early disable for all GTs
    (drivers/gpu/drm/xe/xe_pm.c:570-572).
  - No architectural changes, no interface changes, no behavior changes
    outside resume paths.

- Correct technical fix: The helper `xe_gt_idle_disable_c6()` safely
  forces GT out of RC6 before resume proceeds:
  - Implementation clears RC6 and RC state under forcewake and is a no-
    op on VFs (drivers/gpu/drm/xe/xe_gt_idle.c:389-407).
  - If forcewake is not available yet, it returns `-ETIMEDOUT`; the
    resume continues without regressing behavior (callers ignore return,
    which is acceptable to prevent blocking resume).

- Proper handoff to re-enable C-states: RC6 is re-enabled by GuC Power
  Conservation once firmware is up, or explicitly when GuC PC is
  skipped:
  - `xe_uc_load_hw()` starts GuC PC during GT bringup
    (drivers/gpu/drm/xe/xe_uc.c:215).
  - If GuC PC is skipped, RC6 is explicitly re-enabled via
    `xe_gt_idle_enable_c6(gt)` (drivers/gpu/drm/xe/xe_guc_pc.c:1257).
  - Thus the “keep GT awake only until GuC takes over” intent is
    fulfilled, avoiding prolonged power impact.

- Low regression risk:
  - Scope limited to early resume time; worst-case effect is slightly
    higher power during resume window.
  - No changes to suspend sequencing, only resume entry.
  - SR-IOV VFs unaffected (helper is no-op there).
  - Resume sequences already transition to GuC-controlled power states,
    so this change aligns with existing design.

- Stable backport suitability:
  - Bug fix with user impact (instability/corruption) and a minimal,
    targeted change.
  - No new features or ABI changes.
  - Touches the `drm/xe` driver only, not core subsystems.
  - If a target stable branch predates `xe_gt_idle_disable_c6()` or
    `xe_gt_idle.h`, the backport must include or adapt to the equivalent
    RC6 control helper; otherwise this applies cleanly.

Overall, this is a classic stable-worthy fix: minimal, isolated, and
prevents real-world resume failures without architectural churn.

 drivers/gpu/drm/xe/xe_pm.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xe/xe_pm.c b/drivers/gpu/drm/xe/xe_pm.c
index 3e301e42b2f19..9fccc7a855f30 100644
--- a/drivers/gpu/drm/xe/xe_pm.c
+++ b/drivers/gpu/drm/xe/xe_pm.c
@@ -18,7 +18,7 @@
 #include "xe_device.h"
 #include "xe_ggtt.h"
 #include "xe_gt.h"
-#include "xe_guc.h"
+#include "xe_gt_idle.h"
 #include "xe_i2c.h"
 #include "xe_irq.h"
 #include "xe_pcode.h"
@@ -177,6 +177,9 @@ int xe_pm_resume(struct xe_device *xe)
 	drm_dbg(&xe->drm, "Resuming device\n");
 	trace_xe_pm_resume(xe, __builtin_return_address(0));
 
+	for_each_gt(gt, xe, id)
+		xe_gt_idle_disable_c6(gt);
+
 	for_each_tile(tile, xe, id)
 		xe_wa_apply_tile_workarounds(tile);
 
@@ -547,6 +550,9 @@ int xe_pm_runtime_resume(struct xe_device *xe)
 
 	xe_rpm_lockmap_acquire(xe);
 
+	for_each_gt(gt, xe, id)
+		xe_gt_idle_disable_c6(gt);
+
 	if (xe->d3cold.allowed) {
 		err = xe_pcode_ready(xe, true);
 		if (err)
-- 
2.51.0