/* 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__); \
                /* Guarantee COND check prior to timeout */             \
                barrier();                                              \
                OP;                                                     \
                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__ */