drm/i915: split out i915_wait_util.h

Move waiting related utilities from i915_utils.h to separate new file
i915_wait_util.h. Clean up related includes.

Note: Many of the various wait macro usages could likely be refactored
to use poll_timeout_us().

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://lore.kernel.org/r/431396ac8cdb3e2f4ff053a8933290289a66ce42.1757582214.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/i915_wait_util.h

@@ -0,0 +1,119 @@
+/* SPDX-License-Identifier: MIT */
+/* Copyright © 2025 Intel Corporation */
+
+#ifndef __I915_WAIT_UTIL_H__
+#define __I915_WAIT_UTIL_H__
+
+#include <linux/compiler.h>
+#include <linux/delay.h>
+#include <linux/ktime.h>
+#include <linux/sched/clock.h>
+#include <linux/smp.h>
+
+/*
+ * __wait_for - magic wait macro
+ *
+ * Macro to help avoid open coding check/wait/timeout patterns. Note that it's
+ * important that we check the condition again after having timed out, since the
+ * timeout could be due to preemption or similar and we've never had a chance to
+ * check the condition before the timeout.
+ */
+#define __wait_for(OP, COND, US, Wmin, Wmax) ({ \
+	const ktime_t end__ = ktime_add_ns(ktime_get_raw(), 1000ll * (US)); \
+	long wait__ = (Wmin); /* recommended min for usleep is 10 us */	\
+	int ret__;							\
+	might_sleep();							\
+	for (;;) {							\
+		const bool expired__ = ktime_after(ktime_get_raw(), end__); \
+		OP;							\
+		/* Guarantee COND check prior to timeout */		\
+		barrier();						\
+		if (COND) {						\
+			ret__ = 0;					\
+			break;						\
+		}							\
+		if (expired__) {					\
+			ret__ = -ETIMEDOUT;				\
+			break;						\
+		}							\
+		usleep_range(wait__, wait__ * 2);			\
+		if (wait__ < (Wmax))					\
+			wait__ <<= 1;					\
+	}								\
+	ret__;								\
+})
+
+#define _wait_for(COND, US, Wmin, Wmax)	__wait_for(, (COND), (US), (Wmin), \
+						   (Wmax))
+#define wait_for(COND, MS)		_wait_for((COND), (MS) * 1000, 10, 1000)
+
+/*
+ * If CONFIG_PREEMPT_COUNT is disabled, in_atomic() always reports false.
+ * On PREEMPT_RT the context isn't becoming atomic because it is used in an
+ * interrupt handler or because a spinlock_t is acquired. This leads to
+ * warnings which don't occur otherwise and therefore the check is disabled.
+ */
+#if IS_ENABLED(CONFIG_DRM_I915_DEBUG) && IS_ENABLED(CONFIG_PREEMPT_COUNT) && !defined(CONFIG_PREEMPT_RT)
+# define _WAIT_FOR_ATOMIC_CHECK(ATOMIC) WARN_ON_ONCE((ATOMIC) && !in_atomic())
+#else
+# define _WAIT_FOR_ATOMIC_CHECK(ATOMIC) do { } while (0)
+#endif
+
+#define _wait_for_atomic(COND, US, ATOMIC) \
+({ \
+	int cpu, ret, timeout = (US) * 1000; \
+	u64 base; \
+	_WAIT_FOR_ATOMIC_CHECK(ATOMIC); \
+	if (!(ATOMIC)) { \
+		preempt_disable(); \
+		cpu = smp_processor_id(); \
+	} \
+	base = local_clock(); \
+	for (;;) { \
+		u64 now = local_clock(); \
+		if (!(ATOMIC)) \
+			preempt_enable(); \
+		/* Guarantee COND check prior to timeout */ \
+		barrier(); \
+		if (COND) { \
+			ret = 0; \
+			break; \
+		} \
+		if (now - base >= timeout) { \
+			ret = -ETIMEDOUT; \
+			break; \
+		} \
+		cpu_relax(); \
+		if (!(ATOMIC)) { \
+			preempt_disable(); \
+			if (unlikely(cpu != smp_processor_id())) { \
+				timeout -= now - base; \
+				cpu = smp_processor_id(); \
+				base = local_clock(); \
+			} \
+		} \
+	} \
+	ret; \
+})
+
+#define wait_for_us(COND, US) \
+({ \
+	int ret__; \
+	BUILD_BUG_ON(!__builtin_constant_p(US)); \
+	if ((US) > 10) \
+		ret__ = _wait_for((COND), (US), 10, 10); \
+	else \
+		ret__ = _wait_for_atomic((COND), (US), 0); \
+	ret__; \
+})
+
+#define wait_for_atomic_us(COND, US) \
+({ \
+	BUILD_BUG_ON(!__builtin_constant_p(US)); \
+	BUILD_BUG_ON((US) > 50000); \
+	_wait_for_atomic((COND), (US), 1); \
+})
+
+#define wait_for_atomic(COND, MS) wait_for_atomic_us((COND), (MS) * 1000)
+
+#endif /* __I915_WAIT_UTIL_H__ */