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    Subject[PATCH v2 05/14] drm/panfrost: use spinlock instead of atomic
    Date
    Convert busy_count to a simple int protected by spinlock.

    Signed-off-by: Clément Péron <peron.clem@gmail.com>
    Reviewed-by: Steven Price <steven.price@arm.com>
    ---
    drivers/gpu/drm/panfrost/panfrost_devfreq.c | 43 +++++++++++++++------
    drivers/gpu/drm/panfrost/panfrost_devfreq.h | 9 ++++-
    2 files changed, 40 insertions(+), 12 deletions(-)

    diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.c b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
    index 962550363391..78753cfb59fb 100644
    --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.c
    +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
    @@ -12,16 +12,12 @@

    static void panfrost_devfreq_update_utilization(struct panfrost_devfreq *pfdevfreq)
    {
    - ktime_t now;
    - ktime_t last;
    -
    - if (!pfdevfreq->devfreq)
    - return;
    + ktime_t now, last;

    now = ktime_get();
    last = pfdevfreq->time_last_update;

    - if (atomic_read(&pfdevfreq->busy_count) > 0)
    + if (pfdevfreq->busy_count > 0)
    pfdevfreq->busy_time += ktime_sub(now, last);
    else
    pfdevfreq->idle_time += ktime_sub(now, last);
    @@ -59,10 +55,14 @@ static int panfrost_devfreq_get_dev_status(struct device *dev,
    {
    struct panfrost_device *pfdev = dev_get_drvdata(dev);
    struct panfrost_devfreq *pfdevfreq = &pfdev->pfdevfreq;
    + unsigned long irqflags;
    +
    + status->current_frequency = clk_get_rate(pfdev->clock);
    +
    + spin_lock_irqsave(&pfdevfreq->lock, irqflags);

    panfrost_devfreq_update_utilization(pfdevfreq);

    - status->current_frequency = clk_get_rate(pfdev->clock);
    status->total_time = ktime_to_ns(ktime_add(pfdevfreq->busy_time,
    pfdevfreq->idle_time));

    @@ -70,6 +70,8 @@ static int panfrost_devfreq_get_dev_status(struct device *dev,

    panfrost_devfreq_reset(pfdevfreq);

    + spin_unlock_irqrestore(&pfdevfreq->lock, irqflags);
    +
    dev_dbg(pfdev->dev, "busy %lu total %lu %lu %% freq %lu MHz\n",
    status->busy_time, status->total_time,
    status->busy_time / (status->total_time / 100),
    @@ -100,6 +102,8 @@ int panfrost_devfreq_init(struct panfrost_device *pfdev)
    else if (ret)
    return ret;

    + spin_lock_init(&pfdevfreq->lock);
    +
    panfrost_devfreq_reset(pfdevfreq);

    cur_freq = clk_get_rate(pfdev->clock);
    @@ -162,15 +166,32 @@ void panfrost_devfreq_suspend(struct panfrost_device *pfdev)

    void panfrost_devfreq_record_busy(struct panfrost_devfreq *pfdevfreq)
    {
    + unsigned long irqflags;
    +
    + if (!pfdevfreq->devfreq)
    + return;
    +
    + spin_lock_irqsave(&pfdevfreq->lock, irqflags);
    +
    panfrost_devfreq_update_utilization(pfdevfreq);
    - atomic_inc(&pfdevfreq->busy_count);
    +
    + pfdevfreq->busy_count++;
    +
    + spin_unlock_irqrestore(&pfdevfreq->lock, irqflags);
    }

    void panfrost_devfreq_record_idle(struct panfrost_devfreq *pfdevfreq)
    {
    - int count;
    + unsigned long irqflags;
    +
    + if (!pfdevfreq->devfreq)
    + return;
    +
    + spin_lock_irqsave(&pfdevfreq->lock, irqflags);

    panfrost_devfreq_update_utilization(pfdevfreq);
    - count = atomic_dec_if_positive(&pfdevfreq->busy_count);
    - WARN_ON(count < 0);
    +
    + WARN_ON(--pfdevfreq->busy_count < 0);
    +
    + spin_unlock_irqrestore(&pfdevfreq->lock, irqflags);
    }
    diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.h b/drivers/gpu/drm/panfrost/panfrost_devfreq.h
    index 0697f8d5aa34..3392df1020be 100644
    --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.h
    +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.h
    @@ -4,6 +4,7 @@
    #ifndef __PANFROST_DEVFREQ_H__
    #define __PANFROST_DEVFREQ_H__

    +#include <linux/spinlock.h>
    #include <linux/ktime.h>

    struct devfreq;
    @@ -14,10 +15,16 @@ struct panfrost_device;
    struct panfrost_devfreq {
    struct devfreq *devfreq;
    struct thermal_cooling_device *cooling;
    +
    ktime_t busy_time;
    ktime_t idle_time;
    ktime_t time_last_update;
    - atomic_t busy_count;
    + int busy_count;
    + /*
    + * Protect busy_time, idle_time, time_last_update and busy_count
    + * because these can be updated concurrently between multiple jobs.
    + */
    + spinlock_t lock;
    };

    int panfrost_devfreq_init(struct panfrost_device *pfdev);
    --
    2.25.1
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