drm/xe/bmg: Update Wa_22019338487

Limit GT max frequency to 2600MHz and wait for frequency to reduce
before proceeding with a transient flush. This is really only needed for
the transient flush: if L2 flush is needed due to 16023588340 then
there's no need to do this additional wait since we are already using
the bigger hammer.

v2: Use generic names, ensure user set max frequency requests wait
for flush to complete (Rodrigo)
v3:
 - User requests wait via wait_var_event_timeout (Lucas)
 - Close races on flush + user requests (Lucas)
 - Fix xe_guc_pc_remove_flush_freq_limit() being called on last gt
   rather than root gt (Lucas)
v4:
 - Only apply the freq reducing part if a TDF is needed: L2 flush trumps
   the need for waiting a lower frequency

Fixes: aaa0807 ("drm/xe/bmg: Apply Wa_22019338487")
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
Link: https://lore.kernel.org/r/20250618-wa-22019338487-v5-4-b888388477f2@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
(cherry picked from commit deea6a7)
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

Author: vsbelgaum

drivers/gpu/drm/xe/xe_device.c

@@ -40,6 +40,7 @@
 #include "xe_gt_printk.h"
 #include "xe_gt_sriov_vf.h"
 #include "xe_guc.h"
+#include "xe_guc_pc.h"
 #include "xe_hw_engine_group.h"
 #include "xe_hwmon.h"
 #include "xe_irq.h"
@@ -1071,11 +1072,14 @@ void xe_device_td_flush(struct xe_device *xe)
 		return;
 
 	root_gt = xe_root_mmio_gt(xe);
-	if (XE_WA(root_gt, 16023588340))
+	if (XE_WA(root_gt, 16023588340)) {
 		/* A transient flush is not sufficient: flush the L2 */
 		xe_device_l2_flush(xe);
-	else
+	} else {
+		xe_guc_pc_apply_flush_freq_limit(&root_gt->uc.guc.pc);
 		tdf_request_sync(xe);
+		xe_guc_pc_remove_flush_freq_limit(&root_gt->uc.guc.pc);
+	}
 }
 
 u32 xe_device_ccs_bytes(struct xe_device *xe, u64 size)

drivers/gpu/drm/xe/xe_guc_pc.c

@@ -7,7 +7,9 @@
 
 #include <linux/cleanup.h>
 #include <linux/delay.h>
+#include <linux/jiffies.h>
 #include <linux/ktime.h>
+#include <linux/wait_bit.h>
 
 #include <drm/drm_managed.h>
 #include <drm/drm_print.h>
@@ -53,9 +55,11 @@
 #define LNL_MERT_FREQ_CAP	800
 #define BMG_MERT_FREQ_CAP	2133
 #define BMG_MIN_FREQ		1200
+#define BMG_MERT_FLUSH_FREQ_CAP	2600
 
 #define SLPC_RESET_TIMEOUT_MS 5 /* roughly 5ms, but no need for precision */
 #define SLPC_RESET_EXTENDED_TIMEOUT_MS 1000 /* To be used only at pc_start */
+#define SLPC_ACT_FREQ_TIMEOUT_MS 100
 
 /**
  * DOC: GuC Power Conservation (PC)
@@ -143,6 +147,36 @@ static int wait_for_pc_state(struct xe_guc_pc *pc,
 	return -ETIMEDOUT;
 }
 
+static int wait_for_flush_complete(struct xe_guc_pc *pc)
+{
+	const unsigned long timeout = msecs_to_jiffies(30);
+
+	if (!wait_var_event_timeout(&pc->flush_freq_limit,
+				    !atomic_read(&pc->flush_freq_limit),
+				    timeout))
+		return -ETIMEDOUT;
+
+	return 0;
+}
+
+static int wait_for_act_freq_limit(struct xe_guc_pc *pc, u32 freq)
+{
+	int timeout_us = SLPC_ACT_FREQ_TIMEOUT_MS * USEC_PER_MSEC;
+	int slept, wait = 10;
+
+	for (slept = 0; slept < timeout_us;) {
+		if (xe_guc_pc_get_act_freq(pc) <= freq)
+			return 0;
+
+		usleep_range(wait, wait << 1);
+		slept += wait;
+		wait <<= 1;
+		if (slept + wait > timeout_us)
+			wait = timeout_us - slept;
+	}
+
+	return -ETIMEDOUT;
+}
 static int pc_action_reset(struct xe_guc_pc *pc)
 {
 	struct xe_guc_ct *ct = pc_to_ct(pc);
@@ -688,6 +722,11 @@ static int xe_guc_pc_set_max_freq_locked(struct xe_guc_pc *pc, u32 freq)
  */
 int xe_guc_pc_set_max_freq(struct xe_guc_pc *pc, u32 freq)
 {
+	if (XE_WA(pc_to_gt(pc), 22019338487)) {
+		if (wait_for_flush_complete(pc) != 0)
+			return -EAGAIN;
+	}
+
 	guard(mutex)(&pc->freq_lock);
 
 	return xe_guc_pc_set_max_freq_locked(pc, freq);
@@ -888,6 +927,92 @@ static int pc_adjust_requested_freq(struct xe_guc_pc *pc)
 	return ret;
 }
 
+static bool needs_flush_freq_limit(struct xe_guc_pc *pc)
+{
+	struct xe_gt *gt = pc_to_gt(pc);
+
+	return  XE_WA(gt, 22019338487) &&
+		pc->rp0_freq > BMG_MERT_FLUSH_FREQ_CAP;
+}
+
+/**
+ * xe_guc_pc_apply_flush_freq_limit() - Limit max GT freq during L2 flush
+ * @pc: the xe_guc_pc object
+ *
+ * As per the WA, reduce max GT frequency during L2 cache flush
+ */
+void xe_guc_pc_apply_flush_freq_limit(struct xe_guc_pc *pc)
+{
+	struct xe_gt *gt = pc_to_gt(pc);
+	u32 max_freq;
+	int ret;
+
+	if (!needs_flush_freq_limit(pc))
+		return;
+
+	guard(mutex)(&pc->freq_lock);
+
+	ret = xe_guc_pc_get_max_freq_locked(pc, &max_freq);
+	if (!ret && max_freq > BMG_MERT_FLUSH_FREQ_CAP) {
+		ret = pc_set_max_freq(pc, BMG_MERT_FLUSH_FREQ_CAP);
+		if (ret) {
+			xe_gt_err_once(gt, "Failed to cap max freq on flush to %u, %pe\n",
+				       BMG_MERT_FLUSH_FREQ_CAP, ERR_PTR(ret));
+			return;
+		}
+
+		atomic_set(&pc->flush_freq_limit, 1);
+
+		/*
+		 * If user has previously changed max freq, stash that value to
+		 * restore later, otherwise use the current max. New user
+		 * requests wait on flush.
+		 */
+		if (pc->user_requested_max != 0)
+			pc->stashed_max_freq = pc->user_requested_max;
+		else
+			pc->stashed_max_freq = max_freq;
+	}
+
+	/*
+	 * Wait for actual freq to go below the flush cap: even if the previous
+	 * max was below cap, the current one might still be above it
+	 */
+	ret = wait_for_act_freq_limit(pc, BMG_MERT_FLUSH_FREQ_CAP);
+	if (ret)
+		xe_gt_err_once(gt, "Actual freq did not reduce to %u, %pe\n",
+			       BMG_MERT_FLUSH_FREQ_CAP, ERR_PTR(ret));
+}
+
+/**
+ * xe_guc_pc_remove_flush_freq_limit() - Remove max GT freq limit after L2 flush completes.
+ * @pc: the xe_guc_pc object
+ *
+ * Retrieve the previous GT max frequency value.
+ */
+void xe_guc_pc_remove_flush_freq_limit(struct xe_guc_pc *pc)
+{
+	struct xe_gt *gt = pc_to_gt(pc);
+	int ret = 0;
+
+	if (!needs_flush_freq_limit(pc))
+		return;
+
+	if (!atomic_read(&pc->flush_freq_limit))
+		return;
+
+	mutex_lock(&pc->freq_lock);
+
+	ret = pc_set_max_freq(&gt->uc.guc.pc, pc->stashed_max_freq);
+	if (ret)
+		xe_gt_err_once(gt, "Failed to restore max freq %u:%d",
+			       pc->stashed_max_freq, ret);
+
+	atomic_set(&pc->flush_freq_limit, 0);
+	mutex_unlock(&pc->freq_lock);
+	wake_up_var(&pc->flush_freq_limit);
+}
+
 static int pc_set_mert_freq_cap(struct xe_guc_pc *pc)
 {
 	int ret;

drivers/gpu/drm/xe/xe_guc_pc.h

@@ -38,5 +38,7 @@ u64 xe_guc_pc_mc6_residency(struct xe_guc_pc *pc);
 void xe_guc_pc_init_early(struct xe_guc_pc *pc);
 int xe_guc_pc_restore_stashed_freq(struct xe_guc_pc *pc);
 void xe_guc_pc_raise_unslice(struct xe_guc_pc *pc);
+void xe_guc_pc_apply_flush_freq_limit(struct xe_guc_pc *pc);
+void xe_guc_pc_remove_flush_freq_limit(struct xe_guc_pc *pc);
 
 #endif /* _XE_GUC_PC_H_ */

drivers/gpu/drm/xe/xe_guc_pc_types.h

@@ -15,6 +15,8 @@
 struct xe_guc_pc {
 	/** @bo: GGTT buffer object that is shared with GuC PC */
 	struct xe_bo *bo;
+	/** @flush_freq_limit: 1 when max freq changes are limited by driver */
+	atomic_t flush_freq_limit;
 	/** @rp0_freq: HW RP0 frequency - The Maximum one */
 	u32 rp0_freq;
 	/** @rpa_freq: HW RPa frequency - The Achievable one */