drm/i915: split out i915_timer_util.[ch]

Move timer related utilities from i915_utils.[ch] to separate new files
i915_timer_util.[ch]. Clean up related includes.

Note: Arguably none of this should exist in i915 in the first place. At
least isolate it better.

Reviewed-by: Rodrigo Vivi <[e-mail]>
Link: https://lore.kernel.org/r/0a8[e-mail]
Signed-off-by: Jani Nikula <[e-mail]>

drivers/gpu/drm/i915/Makefile

···
 	i915_scatterlist.o \
 	i915_switcheroo.o \
 	i915_sysfs.o \
+	i915_timer_util.o \
 	i915_utils.o \
 	intel_clock_gating.o \
 	intel_cpu_info.o \

drivers/gpu/drm/i915/gt/intel_execlists_submission.c

···
  * preemption, but just sampling the new tail pointer).
  *
  */
+
 #include <linux/interrupt.h>
 #include <linux/string_helpers.h>
 
+#include "gen8_engine_cs.h"
 #include "i915_drv.h"
 #include "i915_reg.h"
+#include "i915_timer_util.h"
 #include "i915_trace.h"
 #include "i915_vgpu.h"
-#include "gen8_engine_cs.h"
 #include "intel_breadcrumbs.h"
 #include "intel_context.h"
 #include "intel_engine_heartbeat.h"

drivers/gpu/drm/i915/gt/sysfs_engines.c

···
 #include <linux/sysfs.h>
 
 #include "i915_drv.h"
+#include "i915_timer_util.h"
 #include "intel_engine.h"
 #include "intel_engine_heartbeat.h"
 #include "sysfs_engines.h"

drivers/gpu/drm/i915/i915_timer_util.c

···
+// SPDX-License-Identifier: MIT
+/* Copyright © 2025 Intel Corporation */
+
+#include <linux/jiffies.h>
+
+#include "i915_timer_util.h"
+
+void cancel_timer(struct timer_list *t)
+{
+	if (!timer_active(t))
+		return;
+
+	timer_delete(t);
+	WRITE_ONCE(t->expires, 0);
+}
+
+void set_timer_ms(struct timer_list *t, unsigned long timeout)
+{
+	if (!timeout) {
+		cancel_timer(t);
+		return;
+	}
+
+	timeout = msecs_to_jiffies(timeout);
+
+	/*
+	 * Paranoia to make sure the compiler computes the timeout before
+	 * loading 'jiffies' as jiffies is volatile and may be updated in
+	 * the background by a timer tick. All to reduce the complexity
+	 * of the addition and reduce the risk of losing a jiffy.
+	 */
+	barrier();
+
+	/* Keep t->expires = 0 reserved to indicate a canceled timer. */
+	mod_timer(t, jiffies + timeout ?: 1);
+}

drivers/gpu/drm/i915/i915_timer_util.h

···
+/* SPDX-License-Identifier: MIT */
+/* Copyright © 2025 Intel Corporation */
+
+#ifndef __I915_TIMER_UTIL_H__
+#define __I915_TIMER_UTIL_H__
+
+#include <linux/timer.h>
+#include <asm/rwonce.h>
+
+void cancel_timer(struct timer_list *t);
+void set_timer_ms(struct timer_list *t, unsigned long timeout);
+
+static inline bool timer_active(const struct timer_list *t)
+{
+	return READ_ONCE(t->expires);
+}
+
+static inline bool timer_expired(const struct timer_list *t)
+{
+	return timer_active(t) && !timer_pending(t);
+}
+
+#endif /* __I915_TIMER_UTIL_H__ */

drivers/gpu/drm/i915/i915_utils.c

···
 
 #endif
 
-void cancel_timer(struct timer_list *t)
-{
-	if (!timer_active(t))
-		return;
-
-	timer_delete(t);
-	WRITE_ONCE(t->expires, 0);
-}
-
-void set_timer_ms(struct timer_list *t, unsigned long timeout)
-{
-	if (!timeout) {
-		cancel_timer(t);
-		return;
-	}
-
-	timeout = msecs_to_jiffies(timeout);
-
-	/*
-	 * Paranoia to make sure the compiler computes the timeout before
-	 * loading 'jiffies' as jiffies is volatile and may be updated in
-	 * the background by a timer tick. All to reduce the complexity
-	 * of the addition and reduce the risk of losing a jiffy.
-	 */
-	barrier();
-
-	/* Keep t->expires = 0 reserved to indicate a canceled timer. */
-	mod_timer(t, jiffies + timeout ?: 1);
-}
-
 bool i915_vtd_active(struct drm_i915_private *i915)
 {
 	if (device_iommu_mapped(i915->drm.dev))

drivers/gpu/drm/i915/i915_utils.h

···
 #endif
 
 struct drm_i915_private;
-struct timer_list;
 
 #define MISSING_CASE(x) WARN(1, "Missing case (%s == %ld)\n", \
 			     __stringify(x), (long)(x))
···
 	 * the machine if the kernel is tainted.
 	 */
 	add_taint(taint, LOCKDEP_STILL_OK);
-}
-
-void cancel_timer(struct timer_list *t);
-void set_timer_ms(struct timer_list *t, unsigned long timeout);
-
-static inline bool timer_active(const struct timer_list *t)
-{
-	return READ_ONCE(t->expires);
-}
-
-static inline bool timer_expired(const struct timer_list *t)
-{
-	return timer_active(t) && !timer_pending(t);
 }
 
 static inline bool i915_run_as_guest(void)