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/* 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__ */
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