// SPDX-License-Identifier: GPL-2.0
// Copyright (C) 2017 Thomas Gleixner <tglx@linutronix.de>

#include <linux/spinlock.h>
#include <linux/seq_file.h>
#include <linux/bitmap.h>
#include <linux/percpu.h>
#include <linux/cpu.h>
#include <linux/irq.h>

#define IRQ_MATRIX_SIZE (BITS_TO_LONGS(IRQ_MATRIX_BITS))

struct cpumap {
        unsigned int            available;
        unsigned int            allocated;
        unsigned int            managed;
        unsigned int            managed_allocated;
        bool                    initialized;
        bool                    online;
        unsigned long           alloc_map[IRQ_MATRIX_SIZE];
        unsigned long           managed_map[IRQ_MATRIX_SIZE];
};

struct irq_matrix {
        unsigned int            matrix_bits;
        unsigned int            alloc_start;
        unsigned int            alloc_end;
        unsigned int            alloc_size;
        unsigned int            global_available;
        unsigned int            global_reserved;
        unsigned int            systembits_inalloc;
        unsigned int            total_allocated;
        unsigned int            online_maps;
        struct cpumap __percpu  *maps;
        unsigned long           scratch_map[IRQ_MATRIX_SIZE];
        unsigned long           system_map[IRQ_MATRIX_SIZE];
};

#define CREATE_TRACE_POINTS
#include <trace/events/irq_matrix.h>

/**
 * irq_alloc_matrix - Allocate a irq_matrix structure and initialize it
 * @matrix_bits:        Number of matrix bits must be <= IRQ_MATRIX_BITS
 * @alloc_start:        From which bit the allocation search starts
 * @alloc_end:          At which bit the allocation search ends, i.e first
 *                      invalid bit
 */
__init struct irq_matrix *irq_alloc_matrix(unsigned int matrix_bits,
                                           unsigned int alloc_start,
                                           unsigned int alloc_end)
{
        struct irq_matrix *m;

        if (matrix_bits > IRQ_MATRIX_BITS)
                return NULL;

        m = kzalloc(sizeof(*m), GFP_KERNEL);
        if (!m)
                return NULL;

        m->matrix_bits = matrix_bits;
        m->alloc_start = alloc_start;
        m->alloc_end = alloc_end;
        m->alloc_size = alloc_end - alloc_start;
        m->maps = alloc_percpu(*m->maps);
        if (!m->maps) {
                kfree(m);
                return NULL;
        }
        return m;
}

/**
 * irq_matrix_online - Bring the local CPU matrix online
 * @m:          Matrix pointer
 */
void irq_matrix_online(struct irq_matrix *m)
{
        struct cpumap *cm = this_cpu_ptr(m->maps);

        BUG_ON(cm->online);

        if (!cm->initialized) {
                cm->available = m->alloc_size;
                cm->available -= cm->managed + m->systembits_inalloc;
                cm->initialized = true;
        }
        m->global_available += cm->available;
        cm->online = true;
        m->online_maps++;
        trace_irq_matrix_online(m);
}

/**
 * irq_matrix_offline - Bring the local CPU matrix offline
 * @m:          Matrix pointer
 */
void irq_matrix_offline(struct irq_matrix *m)
{
        struct cpumap *cm = this_cpu_ptr(m->maps);

        /* Update the global available size */
        m->global_available -= cm->available;
        cm->online = false;
        m->online_maps--;
        trace_irq_matrix_offline(m);
}

static unsigned int matrix_alloc_area(struct irq_matrix *m, struct cpumap *cm,
                                      unsigned int num, bool managed)
{
        unsigned int area, start = m->alloc_start;
        unsigned int end = m->alloc_end;

        bitmap_or(m->scratch_map, cm->managed_map, m->system_map, end);
        bitmap_or(m->scratch_map, m->scratch_map, cm->alloc_map, end);
        area = bitmap_find_next_zero_area(m->scratch_map, end, start, num, 0);
        if (area >= end)
                return area;
        if (managed)
                bitmap_set(cm->managed_map, area, num);
        else
                bitmap_set(cm->alloc_map, area, num);
        return area;
}

/* Find the best CPU which has the lowest vector allocation count */
static unsigned int matrix_find_best_cpu(struct irq_matrix *m,
                                        const struct cpumask *msk)
{
        unsigned int cpu, best_cpu, maxavl = 0;
        struct cpumap *cm;

        best_cpu = UINT_MAX;

        for_each_cpu(cpu, msk) {
                cm = per_cpu_ptr(m->maps, cpu);

                if (!cm->online || cm->available <= maxavl)
                        continue;

                best_cpu = cpu;
                maxavl = cm->available;
        }
        return best_cpu;
}

/* Find the best CPU which has the lowest number of managed IRQs allocated */
static unsigned int matrix_find_best_cpu_managed(struct irq_matrix *m,
                                                const struct cpumask *msk)
{
        unsigned int cpu, best_cpu, allocated = UINT_MAX;
        struct cpumap *cm;

        best_cpu = UINT_MAX;

        for_each_cpu(cpu, msk) {
                cm = per_cpu_ptr(m->maps, cpu);

                if (!cm->online || cm->managed_allocated > allocated)
                        continue;

                best_cpu = cpu;
                allocated = cm->managed_allocated;
        }
        return best_cpu;
}

/**
 * irq_matrix_assign_system - Assign system wide entry in the matrix
 * @m:          Matrix pointer
 * @bit:        Which bit to reserve
 * @replace:    Replace an already allocated vector with a system
 *              vector at the same bit position.
 *
 * The BUG_ON()s below are on purpose. If this goes wrong in the
 * early boot process, then the chance to survive is about zero.
 * If this happens when the system is life, it's not much better.
 */
void irq_matrix_assign_system(struct irq_matrix *m, unsigned int bit,
                              bool replace)
{
        struct cpumap *cm = this_cpu_ptr(m->maps);

        BUG_ON(bit > m->matrix_bits);
        BUG_ON(m->online_maps > 1 || (m->online_maps && !replace));

        set_bit(bit, m->system_map);
        if (replace) {
                BUG_ON(!test_and_clear_bit(bit, cm->alloc_map));
                cm->allocated--;
                m->total_allocated--;
        }
        if (bit >= m->alloc_start && bit < m->alloc_end)
                m->systembits_inalloc++;

        trace_irq_matrix_assign_system(bit, m);
}

/**
 * irq_matrix_reserve_managed - Reserve a managed interrupt in a CPU map
 * @m:          Matrix pointer
 * @msk:        On which CPUs the bits should be reserved.
 *
 * Can be called for offline CPUs. Note, this will only reserve one bit
 * on all CPUs in @msk, but it's not guaranteed that the bits are at the
 * same offset on all CPUs
 */
int irq_matrix_reserve_managed(struct irq_matrix *m, const struct cpumask *msk)
{
        unsigned int cpu, failed_cpu;

        for_each_cpu(cpu, msk) {
                struct cpumap *cm = per_cpu_ptr(m->maps, cpu);
                unsigned int bit;

                bit = matrix_alloc_area(m, cm, 1, true);
                if (bit >= m->alloc_end)
                        goto cleanup;
                cm->managed++;
                if (cm->online) {
                        cm->available--;
                        m->global_available--;
                }
                trace_irq_matrix_reserve_managed(bit, cpu, m, cm);
        }
        return 0;
cleanup:
        failed_cpu = cpu;
        for_each_cpu(cpu, msk) {
                if (cpu == failed_cpu)
                        break;
                irq_matrix_remove_managed(m, cpumask_of(cpu));
        }
        return -ENOSPC;
}

/**
 * irq_matrix_remove_managed - Remove managed interrupts in a CPU map
 * @m:          Matrix pointer
 * @msk:        On which CPUs the bits should be removed
 *
 * Can be called for offline CPUs
 *
 * This removes not allocated managed interrupts from the map. It does
 * not matter which one because the managed interrupts free their
 * allocation when they shut down. If not, the accounting is screwed,
 * but all what can be done at this point is warn about it.
 */
void irq_matrix_remove_managed(struct irq_matrix *m, const struct cpumask *msk)
{
        unsigned int cpu;

        for_each_cpu(cpu, msk) {
                struct cpumap *cm = per_cpu_ptr(m->maps, cpu);
                unsigned int bit, end = m->alloc_end;

                if (WARN_ON_ONCE(!cm->managed))
                        continue;

                /* Get managed bit which are not allocated */
                bitmap_andnot(m->scratch_map, cm->managed_map, cm->alloc_map, end);

                bit = find_first_bit(m->scratch_map, end);
                if (WARN_ON_ONCE(bit >= end))
                        continue;

                clear_bit(bit, cm->managed_map);

                cm->managed--;
                if (cm->online) {
                        cm->available++;
                        m->global_available++;
                }
                trace_irq_matrix_remove_managed(bit, cpu, m, cm);
        }
}

/**
 * irq_matrix_alloc_managed - Allocate a managed interrupt in a CPU map
 * @m:          Matrix pointer
 * @cpu:        On which CPU the interrupt should be allocated
 */
int irq_matrix_alloc_managed(struct irq_matrix *m, const struct cpumask *msk,
                             unsigned int *mapped_cpu)
{
        unsigned int bit, cpu, end = m->alloc_end;
        struct cpumap *cm;

        if (cpumask_empty(msk))
                return -EINVAL;

        cpu = matrix_find_best_cpu_managed(m, msk);
        if (cpu == UINT_MAX)
                return -ENOSPC;

        cm = per_cpu_ptr(m->maps, cpu);
        end = m->alloc_end;
        /* Get managed bit which are not allocated */
        bitmap_andnot(m->scratch_map, cm->managed_map, cm->alloc_map, end);
        bit = find_first_bit(m->scratch_map, end);
        if (bit >= end)
                return -ENOSPC;
        set_bit(bit, cm->alloc_map);
        cm->allocated++;
        cm->managed_allocated++;
        m->total_allocated++;
        *mapped_cpu = cpu;
        trace_irq_matrix_alloc_managed(bit, cpu, m, cm);
        return bit;
}

/**
 * irq_matrix_assign - Assign a preallocated interrupt in the local CPU map
 * @m:          Matrix pointer
 * @bit:        Which bit to mark
 *
 * This should only be used to mark preallocated vectors
 */
void irq_matrix_assign(struct irq_matrix *m, unsigned int bit)
{
        struct cpumap *cm = this_cpu_ptr(m->maps);

        if (WARN_ON_ONCE(bit < m->alloc_start || bit >= m->alloc_end))
                return;
        if (WARN_ON_ONCE(test_and_set_bit(bit, cm->alloc_map)))
                return;
        cm->allocated++;
        m->total_allocated++;
        cm->available--;
        m->global_available--;
        trace_irq_matrix_assign(bit, smp_processor_id(), m, cm);
}

/**
 * irq_matrix_reserve - Reserve interrupts
 * @m:          Matrix pointer
 *
 * This is merily a book keeping call. It increments the number of globally
 * reserved interrupt bits w/o actually allocating them. This allows to
 * setup interrupt descriptors w/o assigning low level resources to it.
 * The actual allocation happens when the interrupt gets activated.
 */
void irq_matrix_reserve(struct irq_matrix *m)
{
        if (m->global_reserved <= m->global_available &&
            m->global_reserved + 1 > m->global_available)
                pr_warn("Interrupt reservation exceeds available resources\n");

        m->global_reserved++;
        trace_irq_matrix_reserve(m);
}

/**
 * irq_matrix_remove_reserved - Remove interrupt reservation
 * @m:          Matrix pointer
 *
 * This is merily a book keeping call. It decrements the number of globally
 * reserved interrupt bits. This is used to undo irq_matrix_reserve() when the
 * interrupt was never in use and a real vector allocated, which undid the
 * reservation.
 */
void irq_matrix_remove_reserved(struct irq_matrix *m)
{
        m->global_reserved--;
        trace_irq_matrix_remove_reserved(m);
}

/**
 * irq_matrix_alloc - Allocate a regular interrupt in a CPU map
 * @m:          Matrix pointer
 * @msk:        Which CPUs to search in
 * @reserved:   Allocate previously reserved interrupts
 * @mapped_cpu: Pointer to store the CPU for which the irq was allocated
 */
int irq_matrix_alloc(struct irq_matrix *m, const struct cpumask *msk,
                     bool reserved, unsigned int *mapped_cpu)
{
        unsigned int cpu, bit;
        struct cpumap *cm;

        cpu = matrix_find_best_cpu(m, msk);
        if (cpu == UINT_MAX)
                return -ENOSPC;

        cm = per_cpu_ptr(m->maps, cpu);
        bit = matrix_alloc_area(m, cm, 1, false);
        if (bit >= m->alloc_end)
                return -ENOSPC;
        cm->allocated++;
        cm->available--;
        m->total_allocated++;
        m->global_available--;
        if (reserved)
                m->global_reserved--;
        *mapped_cpu = cpu;
        trace_irq_matrix_alloc(bit, cpu, m, cm);
        return bit;

}

/**
 * irq_matrix_free - Free allocated interrupt in the matrix
 * @m:          Matrix pointer
 * @cpu:        Which CPU map needs be updated
 * @bit:        The bit to remove
 * @managed:    If true, the interrupt is managed and not accounted
 *              as available.
 */
void irq_matrix_free(struct irq_matrix *m, unsigned int cpu,
                     unsigned int bit, bool managed)
{
        struct cpumap *cm = per_cpu_ptr(m->maps, cpu);

        if (WARN_ON_ONCE(bit < m->alloc_start || bit >= m->alloc_end))
                return;

        clear_bit(bit, cm->alloc_map);
        cm->allocated--;
        if(managed)
                cm->managed_allocated--;

        if (cm->online)
                m->total_allocated--;

        if (!managed) {
                cm->available++;
                if (cm->online)
                        m->global_available++;
        }
        trace_irq_matrix_free(bit, cpu, m, cm);
}

/**
 * irq_matrix_available - Get the number of globally available irqs
 * @m:          Pointer to the matrix to query
 * @cpudown:    If true, the local CPU is about to go down, adjust
 *              the number of available irqs accordingly
 */
unsigned int irq_matrix_available(struct irq_matrix *m, bool cpudown)
{
        struct cpumap *cm = this_cpu_ptr(m->maps);

        if (!cpudown)
                return m->global_available;
        return m->global_available - cm->available;
}

/**
 * irq_matrix_reserved - Get the number of globally reserved irqs
 * @m:          Pointer to the matrix to query
 */
unsigned int irq_matrix_reserved(struct irq_matrix *m)
{
        return m->global_reserved;
}

/**
 * irq_matrix_allocated - Get the number of allocated irqs on the local cpu
 * @m:          Pointer to the matrix to search
 *
 * This returns number of allocated irqs
 */
unsigned int irq_matrix_allocated(struct irq_matrix *m)
{
        struct cpumap *cm = this_cpu_ptr(m->maps);

        return cm->allocated;
}

#ifdef CONFIG_GENERIC_IRQ_DEBUGFS
/**
 * irq_matrix_debug_show - Show detailed allocation information
 * @sf:         Pointer to the seq_file to print to
 * @m:          Pointer to the matrix allocator
 * @ind:        Indentation for the print format
 *
 * Note, this is a lockless snapshot.
 */
void irq_matrix_debug_show(struct seq_file *sf, struct irq_matrix *m, int ind)
{
        unsigned int nsys = bitmap_weight(m->system_map, m->matrix_bits);
        int cpu;

        seq_printf(sf, "Online bitmaps:   %6u\n", m->online_maps);
        seq_printf(sf, "Global available: %6u\n", m->global_available);
        seq_printf(sf, "Global reserved:  %6u\n", m->global_reserved);
        seq_printf(sf, "Total allocated:  %6u\n", m->total_allocated);
        seq_printf(sf, "System: %u: %*pbl\n", nsys, m->matrix_bits,
                   m->system_map);
        seq_printf(sf, "%*s| CPU | avl | man | mac | act | vectors\n", ind, " ");
        cpus_read_lock();
        for_each_online_cpu(cpu) {
                struct cpumap *cm = per_cpu_ptr(m->maps, cpu);

                seq_printf(sf, "%*s %4d  %4u  %4u  %4u %4u  %*pbl\n", ind, " ",
                           cpu, cm->available, cm->managed,
                           cm->managed_allocated, cm->allocated,
                           m->matrix_bits, cm->alloc_map);
        }
        cpus_read_unlock();
}
#endif