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SubjectRe: [PATCH 05/15] drm/panfrost: use spinlock instead of atomic
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On 10/05/2020 17:55, Clément Péron wrote:
> Convert busy_count to a simple int protected by spinlock.
>
> Signed-off-by: Clément Péron <peron.clem@gmail.com>

Looks like a fairly mechanical cleanup.

Reviewed-by: Steven Price <steven.price@arm.com>

> ---
> drivers/gpu/drm/panfrost/panfrost_devfreq.c | 43 +++++++++++++++------
> drivers/gpu/drm/panfrost/panfrost_devfreq.h | 10 ++++-
> 2 files changed, 41 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..e6629900a618 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 +15,17 @@ 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, for example by the GP
> + * and PP interrupts.
> + */
> + spinlock_t lock;
> };
>
> int panfrost_devfreq_init(struct panfrost_device *pfdev);
>

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