[Intel-gfx] [PATCH 36/36] drm/i915: Support per-context user requests for GPU frequency control

Lionel Landwerlin lionel.g.landwerlin at intel.com
Fri Nov 16 11:22:44 UTC 2018


On 16/11/2018 11:14, Joonas Lahtinen wrote:
> Quoting Lionel Landwerlin (2018-11-09 19:51:17)
>> I think we have some interest in reviving this for the performance query
>> use case.
> How are performance queries related?


People want performance measured at a given frequency (usually max).


>
> Regards, Joonas
>
>> Is that on anybody's todo list?
>>
>> Thanks,
>>
>> -
>> Lionel
>>
>> On 14/03/2018 09:37, Chris Wilson wrote:
>>> Often, we find ourselves facing a workload where the user knows in
>>> advance what GPU frequency they require for it to complete in a timely
>>> manner, and using past experience they can outperform the HW assisted
>>> RPS autotuning. An example might be kodi (HTPC) where they know that
>>> video decoding and compositing require a minimum frequency to avoid ever
>>> dropping a frame, or conversely know when they are in a powersaving mode
>>> and would rather have slower updates than ramp up the GPU frequency and
>>> power consumption. Other workloads may defeat the autotuning entirely
>>> and need manual control to meet their performance goals, e.g. bursty
>>> applications which require low latency.
>>>
>>> To accommodate the varying needs of different applications, that may be
>>> running concurrently, we want a more flexible system than a global limit
>>> supplied by sysfs. To this end, we offer the application the option to
>>> set their desired frequency bounds on the context itself, and apply those
>>> bounds when we execute commands from the application, switching between
>>> bounds just as easily as we switch between the clients themselves.
>>>
>>> The clients can query the range supported by the HW, or at least the
>>> range they are restricted to, and then freely select frequencies within
>>> that range that they want to run at. (They can select just a single
>>> frequency if they so choose.) As this is subject to the global limit
>>> supplied by the user in sysfs, and a client can only reduce the range of
>>> frequencies they allow the HW to run at, we allow all clients to adjust
>>> their request (and not restrict raising the minimum to privileged
>>> CAP_SYS_NICE clients).
>>>
>>> Testcase: igt/gem_ctx_freq
>>> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
>>> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
>>> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
>>> Cc: Praveen Paneri <praveen.paneri at intel.com>
>>> Cc: Sagar A Kamble <sagar.a.kamble at intel.com>
>>> ---
>>>    drivers/gpu/drm/i915/i915_debugfs.c                |  16 ++-
>>>    drivers/gpu/drm/i915/i915_drv.h                    |   5 +
>>>    drivers/gpu/drm/i915/i915_gem_context.c            |  54 +++++++++
>>>    drivers/gpu/drm/i915/i915_gem_context.h            |   3 +
>>>    drivers/gpu/drm/i915/intel_gt_pm.c                 | 121 ++++++++++++++++---
>>>    drivers/gpu/drm/i915/intel_gt_pm.h                 |   4 +
>>>    drivers/gpu/drm/i915/intel_guc_submission.c        |  16 ++-
>>>    drivers/gpu/drm/i915/intel_lrc.c                   |  15 +++
>>>    .../gpu/drm/i915/selftests/i915_mock_selftests.h   |   1 +
>>>    drivers/gpu/drm/i915/selftests/intel_gt_pm.c       | 130 +++++++++++++++++++++
>>>    include/uapi/drm/i915_drm.h                        |  20 ++++
>>>    11 files changed, 368 insertions(+), 17 deletions(-)
>>>    create mode 100644 drivers/gpu/drm/i915/selftests/intel_gt_pm.c
>>>
>>> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
>>> index 7c7afdac8c8c..a21b9164ade8 100644
>>> --- a/drivers/gpu/drm/i915/i915_debugfs.c
>>> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
>>> @@ -2191,6 +2191,7 @@ static int i915_rps_boost_info(struct seq_file *m, void *data)
>>>        struct drm_device *dev = &dev_priv->drm;
>>>        struct intel_rps *rps = &dev_priv->gt_pm.rps;
>>>        struct drm_file *file;
>>> +     int n;
>>>    
>>>        seq_printf(m, "GPU busy? %s [%d requests]\n",
>>>                   yesno(dev_priv->gt.awake), dev_priv->gt.active_requests);
>>> @@ -2198,17 +2199,30 @@ static int i915_rps_boost_info(struct seq_file *m, void *data)
>>>        seq_printf(m, "CPU waiting? %d\n", count_irq_waiters(dev_priv));
>>>        seq_printf(m, "Boosts outstanding? %d\n",
>>>                   atomic_read(&rps->num_waiters));
>>> +     seq_printf(m, "Worker pending? %s\n", yesno(work_busy(&rps->work)));
>>>        seq_printf(m, "Frequency requested %d [%d, %d]\n",
>>>                   intel_gpu_freq(dev_priv, rps->freq),
>>>                   intel_gpu_freq(dev_priv, rps->min),
>>>                   intel_gpu_freq(dev_priv, rps->max));
>>> -     seq_printf(m, "  min hard:%d, soft:%d user:%d; max user:%d, soft: %d hard:%d\n",
>>> +     seq_printf(m, "  min hard:%d, soft:%d, ctx:%d, user:%d; max user:%d, ctx:%d, soft:%d, hard:%d\n",
>>>                   intel_gpu_freq(dev_priv, rps->min_freq_hw),
>>>                   intel_gpu_freq(dev_priv, rps->min_freq_soft),
>>> +                intel_gpu_freq(dev_priv, rps->min_freq_context),
>>>                   intel_gpu_freq(dev_priv, rps->min_freq_user),
>>>                   intel_gpu_freq(dev_priv, rps->max_freq_user),
>>> +                intel_gpu_freq(dev_priv, rps->max_freq_context),
>>>                   intel_gpu_freq(dev_priv, rps->max_freq_soft),
>>>                   intel_gpu_freq(dev_priv, rps->max_freq_hw));
>>> +     seq_printf(m, "  engines min: [");
>>> +     for (n = 0; n < ARRAY_SIZE(rps->min_freq_engine); n++)
>>> +             seq_printf(m, "%s%d", n ? ", " : "",
>>> +                        intel_gpu_freq(dev_priv, rps->min_freq_engine[n]));
>>> +     seq_printf(m, "]\n  engines max: [");
>>> +     for (n = 0; n < ARRAY_SIZE(rps->max_freq_engine); n++)
>>> +             seq_printf(m, "%s%d", n ? ", " : "",
>>> +                        intel_gpu_freq(dev_priv, rps->max_freq_engine[n]));
>>> +     seq_printf(m, "]\n");
>>> +
>>>        seq_printf(m, "  idle:%d, efficient:%d, boost:%d\n",
>>>                   intel_gpu_freq(dev_priv, rps->idle_freq),
>>>                   intel_gpu_freq(dev_priv, rps->efficient_freq),
>>> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
>>> index 82e9a58bd65f..d754d44cfbc2 100644
>>> --- a/drivers/gpu/drm/i915/i915_drv.h
>>> +++ b/drivers/gpu/drm/i915/i915_drv.h
>>> @@ -731,6 +731,7 @@ struct intel_rps_ei {
>>>    
>>>    struct intel_rps {
>>>        struct mutex lock;
>>> +     spinlock_t engine_lock; /* protects updates to min/max_freq_context */
>>>        struct work_struct work;
>>>    
>>>        bool active;
>>> @@ -763,6 +764,10 @@ struct intel_rps {
>>>        u8 max_freq_user;       /* Max frequency permitted by the driver */
>>>        u8 min_freq_soft;
>>>        u8 max_freq_soft;
>>> +     u8 min_freq_context;    /* Min frequency permitted by the context */
>>> +     u8 max_freq_context;    /* Max frequency permitted by the context */
>>> +     u8 min_freq_engine[I915_NUM_ENGINES];
>>> +     u8 max_freq_engine[I915_NUM_ENGINES];
>>>    
>>>        u8 idle_freq;           /* Frequency to request when we are idle */
>>>        u8 efficient_freq;      /* AKA RPe. Pre-determined balanced frequency */
>>> diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
>>> index 65bf92658d92..1d36e2a02479 100644
>>> --- a/drivers/gpu/drm/i915/i915_gem_context.c
>>> +++ b/drivers/gpu/drm/i915/i915_gem_context.c
>>> @@ -88,8 +88,10 @@
>>>    #include <linux/log2.h>
>>>    #include <drm/drmP.h>
>>>    #include <drm/i915_drm.h>
>>> +
>>>    #include "i915_drv.h"
>>>    #include "i915_trace.h"
>>> +#include "intel_gt_pm.h"
>>>    
>>>    #define ALL_L3_SLICES(dev) (1 << NUM_L3_SLICES(dev)) - 1
>>>    
>>> @@ -281,6 +283,8 @@ __create_hw_context(struct drm_i915_private *dev_priv,
>>>        list_add_tail(&ctx->link, &dev_priv->contexts.list);
>>>        ctx->i915 = dev_priv;
>>>        ctx->priority = I915_PRIORITY_NORMAL;
>>> +     ctx->min_freq = dev_priv->gt_pm.rps.min_freq_hw;
>>> +     ctx->max_freq = dev_priv->gt_pm.rps.max_freq_hw;
>>>    
>>>        INIT_RADIX_TREE(&ctx->handles_vma, GFP_KERNEL);
>>>        INIT_LIST_HEAD(&ctx->handles_list);
>>> @@ -715,6 +719,7 @@ int i915_gem_context_getparam_ioctl(struct drm_device *dev, void *data,
>>>    {
>>>        struct drm_i915_file_private *file_priv = file->driver_priv;
>>>        struct drm_i915_gem_context_param *args = data;
>>> +     struct drm_i915_private *i915 = to_i915(dev);
>>>        struct i915_gem_context *ctx;
>>>        int ret = 0;
>>>    
>>> @@ -747,6 +752,19 @@ int i915_gem_context_getparam_ioctl(struct drm_device *dev, void *data,
>>>        case I915_CONTEXT_PARAM_PRIORITY:
>>>                args->value = ctx->priority;
>>>                break;
>>> +     case I915_CONTEXT_PARAM_FREQUENCY:
>>> +             if (!HAS_RPS(i915) || !HAS_EXECLISTS(i915)) {
>>> +                     ret = -ENODEV;
>>> +             } else if (args->size) {
>>> +                     ret = -EINVAL;
>>> +             } else {
>>> +                     u32 min = intel_gpu_freq(i915, ctx->min_freq);
>>> +                     u32 max = intel_gpu_freq(i915, ctx->max_freq);
>>> +
>>> +                     args->value = I915_CONTEXT_SET_FREQUENCY(min, max);
>>> +             }
>>> +             break;
>>> +
>>>        default:
>>>                ret = -EINVAL;
>>>                break;
>>> @@ -761,6 +779,7 @@ int i915_gem_context_setparam_ioctl(struct drm_device *dev, void *data,
>>>    {
>>>        struct drm_i915_file_private *file_priv = file->driver_priv;
>>>        struct drm_i915_gem_context_param *args = data;
>>> +     struct drm_i915_private *i915 = to_i915(dev);
>>>        struct i915_gem_context *ctx;
>>>        int ret;
>>>    
>>> @@ -821,6 +840,41 @@ int i915_gem_context_setparam_ioctl(struct drm_device *dev, void *data,
>>>                                ctx->priority = priority;
>>>                }
>>>                break;
>>> +     case I915_CONTEXT_PARAM_FREQUENCY:
>>> +             if (!HAS_RPS(i915) || !HAS_EXECLISTS(i915)) {
>>> +                     ret = -ENODEV;
>>> +             } else if (args->size) {
>>> +                     ret = -EINVAL;
>>> +             } else {
>>> +                     struct intel_rps *rps = &i915->gt_pm.rps;
>>> +                     u32 min, max;
>>> +
>>> +                     min = I915_CONTEXT_MIN_FREQUENCY(args->value);
>>> +                     min = intel_freq_opcode(i915, min);
>>> +
>>> +                     max = I915_CONTEXT_MAX_FREQUENCY(args->value);
>>> +                     max = intel_freq_opcode(i915, max);
>>> +
>>> +                     /*
>>> +                      * As we constrain the frequency request from the
>>> +                      * context (application) by the sysadmin imposed limits,
>>> +                      * it is reasonable to allow the application to
>>> +                      * specify its preferred range within those limits.
>>> +                      * That is we do not need to restrict requesting
>>> +                      * a higher frequency to privileged (CAP_SYS_NICE)
>>> +                      * processes.
>>> +                      */
>>> +                     if (max < min) {
>>> +                             ret = -EINVAL;
>>> +                     } else if (min < rps->min_freq_hw ||
>>> +                                max > rps->max_freq_hw) {
>>> +                             ret = -EINVAL;
>>> +                     } else {
>>> +                             ctx->min_freq = min;
>>> +                             ctx->max_freq = max;
>>> +                     }
>>> +             }
>>> +             break;
>>>    
>>>        default:
>>>                ret = -EINVAL;
>>> diff --git a/drivers/gpu/drm/i915/i915_gem_context.h b/drivers/gpu/drm/i915/i915_gem_context.h
>>> index 7854262ddfd9..98f7b71a787a 100644
>>> --- a/drivers/gpu/drm/i915/i915_gem_context.h
>>> +++ b/drivers/gpu/drm/i915/i915_gem_context.h
>>> @@ -150,6 +150,9 @@ struct i915_gem_context {
>>>         */
>>>        int priority;
>>>    
>>> +     u32 min_freq;
>>> +     u32 max_freq;
>>> +
>>>        /** ggtt_offset_bias: placement restriction for context objects */
>>>        u32 ggtt_offset_bias;
>>>    
>>> diff --git a/drivers/gpu/drm/i915/intel_gt_pm.c b/drivers/gpu/drm/i915/intel_gt_pm.c
>>> index 9705205a26b5..4bbfb4080f8f 100644
>>> --- a/drivers/gpu/drm/i915/intel_gt_pm.c
>>> +++ b/drivers/gpu/drm/i915/intel_gt_pm.c
>>> @@ -402,10 +402,10 @@ static int adjust_rps(struct drm_i915_private *dev_priv, int freq, int adj)
>>>        GEM_BUG_ON(!rps->active);
>>>    
>>>        min = clamp_t(int,
>>> -                   rps->min_freq_soft,
>>> +                   max(rps->min_freq_soft, READ_ONCE(rps->min_freq_context)),
>>>                      rps->min_freq_user, rps->max_freq_user);
>>>        max = clamp_t(int,
>>> -                   rps->max_freq_soft,
>>> +                   min(rps->max_freq_soft, READ_ONCE(rps->max_freq_context)),
>>>                      min, rps->max_freq_user);
>>>        if (atomic_read(&rps->num_waiters) && max < rps->boost_freq)
>>>                max = rps->boost_freq;
>>> @@ -809,6 +809,75 @@ void intel_rps_boost(struct i915_request *rq, struct intel_rps_client *client)
>>>        atomic_inc(client ? &client->boosts : &rps->boosts);
>>>    }
>>>    
>>> +static void __rps_update_engine(struct intel_rps *rps,
>>> +                             enum intel_engine_id idx,
>>> +                             u32 min, u32 max)
>>> +{
>>> +     unsigned long flags;
>>> +     bool update = false;
>>> +     u32 old;
>>> +     int n;
>>> +
>>> +     GEM_BUG_ON(min > max);
>>> +
>>> +     if (rps->min_freq_engine[idx] != min) {
>>> +             spin_lock_irqsave(&rps->engine_lock, flags);
>>> +
>>> +             rps->min_freq_engine[idx] = min;
>>> +
>>> +             old = rps->min_freq_context;
>>> +             rps->min_freq_context = rps->min_freq_engine[0];
>>> +             for (n = 1; n < ARRAY_SIZE(rps->min_freq_engine); n++)
>>> +                     if (rps->min_freq_engine[n] > rps->min_freq_context)
>>> +                             rps->min_freq_context = rps->min_freq_engine[n];
>>> +             update |= rps->min_freq_context != old;
>>> +
>>> +             spin_unlock_irqrestore(&rps->engine_lock, flags);
>>> +     }
>>> +
>>> +     if (rps->max_freq_engine[idx] != max) {
>>> +             spin_lock_irqsave(&rps->engine_lock, flags);
>>> +
>>> +             rps->max_freq_engine[idx] = max;
>>> +
>>> +             old = rps->max_freq_context;
>>> +             rps->max_freq_context = rps->max_freq_engine[0];
>>> +             for (n = 1; n < ARRAY_SIZE(rps->max_freq_engine); n++)
>>> +                     if (rps->max_freq_engine[n] < rps->max_freq_context)
>>> +                             rps->max_freq_context = rps->max_freq_engine[n];
>>> +             update |= rps->max_freq_context != old;
>>> +
>>> +             spin_unlock_irqrestore(&rps->engine_lock, flags);
>>> +     }
>>> +
>>> +     /* Kick the RPS worker to apply the updated constraints, as needed */
>>> +     if (update && !atomic_read(&rps->num_waiters)) {
>>> +             old = READ_ONCE(rps->freq);
>>> +             if ((old < min || old > max))
>>> +                     schedule_work(&rps->work);
>>> +     }
>>> +}
>>> +
>>> +void intel_rps_update_engine(const struct intel_engine_cs *engine,
>>> +                          const struct i915_gem_context *ctx)
>>> +{
>>> +     struct intel_rps *rps = &engine->i915->gt_pm.rps;
>>> +     u32 min, max;
>>> +
>>> +     if (!HAS_RPS(engine->i915))
>>> +             return;
>>> +
>>> +     if (ctx) {
>>> +             min = ctx->min_freq;
>>> +             max = ctx->max_freq;
>>> +     } else {
>>> +             min = rps->min_freq_hw;
>>> +             max = rps->max_freq_hw;
>>> +     }
>>> +
>>> +     __rps_update_engine(rps, engine->id, min, max);
>>> +}
>>> +
>>>    static void gen9_disable_rc6(struct drm_i915_private *dev_priv)
>>>    {
>>>        I915_WRITE(GEN6_RC_CONTROL, 0);
>>> @@ -2379,12 +2448,41 @@ void intel_gt_pm_sanitize(struct drm_i915_private *dev_priv)
>>>                gen6_reset_rps_interrupts(dev_priv);
>>>    }
>>>    
>>> +static void intel_rps_init(struct intel_rps *rps)
>>> +{
>>> +     mutex_init(&rps->lock);
>>> +     INIT_WORK(&rps->work, intel_rps_work);
>>> +     spin_lock_init(&rps->engine_lock);
>>> +}
>>> +
>>> +static void intel_rps_init__frequencies(struct intel_rps *rps)
>>> +{
>>> +     int n;
>>> +
>>> +     rps->max_freq_soft = rps->max_freq_hw;
>>> +     rps->min_freq_soft = rps->min_freq_hw;
>>> +
>>> +     rps->max_freq_context = rps->max_freq_hw;
>>> +     rps->min_freq_context = rps->min_freq_hw;
>>> +     for (n = 0; n < ARRAY_SIZE(rps->max_freq_engine); n++) {
>>> +             rps->max_freq_engine[n] = rps->max_freq_hw;
>>> +             rps->min_freq_engine[n] = rps->min_freq_hw;
>>> +     }
>>> +
>>> +     /* Finally allow us to boost to max by default */
>>> +     rps->boost_freq = rps->max_freq_hw;
>>> +     rps->idle_freq = rps->min_freq_hw;
>>> +
>>> +     rps->freq = rps->idle_freq;
>>> +     rps->min = rps->min_freq_hw;
>>> +     rps->max = rps->max_freq_hw;
>>> +}
>>> +
>>>    void intel_gt_pm_init(struct drm_i915_private *dev_priv)
>>>    {
>>>        struct intel_rps *rps = &dev_priv->gt_pm.rps;
>>>    
>>> -     mutex_init(&rps->lock);
>>> -     INIT_WORK(&rps->work, intel_rps_work);
>>> +     intel_rps_init(rps);
>>>    
>>>        if (HAS_GUC_SCHED(dev_priv))
>>>                rps->guc_events = GEN9_GUC_TO_HOST_INT_EVENT;
>>> @@ -2449,16 +2547,7 @@ void intel_gt_pm_init(struct drm_i915_private *dev_priv)
>>>                }
>>>        }
>>>    
>>> -     rps->max_freq_soft = rps->max_freq_hw;
>>> -     rps->min_freq_soft = rps->min_freq_hw;
>>> -
>>> -     /* Finally allow us to boost to max by default */
>>> -     rps->boost_freq = rps->max_freq_hw;
>>> -     rps->idle_freq = rps->min_freq_hw;
>>> -
>>> -     rps->freq = rps->idle_freq;
>>> -     rps->min = rps->min_freq_hw;
>>> -     rps->max = rps->max_freq_hw;
>>> +     intel_rps_init__frequencies(rps);
>>>    
>>>        if (HAS_LLC(dev_priv))
>>>                gen6_update_ring_freq(dev_priv);
>>> @@ -2703,3 +2792,7 @@ void gen9_disable_guc_interrupts(struct drm_i915_private *dev_priv)
>>>    
>>>        gen9_reset_guc_interrupts(dev_priv);
>>>    }
>>> +
>>> +#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
>>> +#include "selftests/intel_gt_pm.c"
>>> +#endif
>>> diff --git a/drivers/gpu/drm/i915/intel_gt_pm.h b/drivers/gpu/drm/i915/intel_gt_pm.h
>>> index 314912c15126..ef3f27eca529 100644
>>> --- a/drivers/gpu/drm/i915/intel_gt_pm.h
>>> +++ b/drivers/gpu/drm/i915/intel_gt_pm.h
>>> @@ -25,7 +25,9 @@
>>>    #define __INTEL_GT_PM_H__
>>>    
>>>    struct drm_i915_private;
>>> +struct i915_gem_context;
>>>    struct i915_request;
>>> +struct intel_engine_cs;
>>>    struct intel_rps_client;
>>>    
>>>    void intel_gpu_ips_init(struct drm_i915_private *dev_priv);
>>> @@ -47,6 +49,8 @@ void intel_gt_pm_idle(struct drm_i915_private *dev_priv);
>>>    
>>>    void intel_gt_pm_irq_handler(struct drm_i915_private *dev_priv, u32 pm_iir);
>>>    
>>> +void intel_rps_update_engine(const struct intel_engine_cs *engine,
>>> +                          const struct i915_gem_context *ctx);
>>>    void intel_rps_boost(struct i915_request *rq, struct intel_rps_client *rps);
>>>    
>>>    int intel_gpu_freq(struct drm_i915_private *dev_priv, int val);
>>> diff --git a/drivers/gpu/drm/i915/intel_guc_submission.c b/drivers/gpu/drm/i915/intel_guc_submission.c
>>> index 8a8ad2fe158d..d8eaae683186 100644
>>> --- a/drivers/gpu/drm/i915/intel_guc_submission.c
>>> +++ b/drivers/gpu/drm/i915/intel_guc_submission.c
>>> @@ -26,9 +26,12 @@
>>>    #include <trace/events/dma_fence.h>
>>>    
>>>    #include "intel_guc_submission.h"
>>> -#include "intel_lrc_reg.h"
>>> +
>>>    #include "i915_drv.h"
>>>    
>>> +#include "intel_gt_pm.h"
>>> +#include "intel_lrc_reg.h"
>>> +
>>>    #define GUC_PREEMPT_FINISHED                0x1
>>>    #define GUC_PREEMPT_BREADCRUMB_DWORDS       0x8
>>>    #define GUC_PREEMPT_BREADCRUMB_BYTES        \
>>> @@ -650,6 +653,12 @@ static void guc_submit(struct intel_engine_cs *engine)
>>>        }
>>>    }
>>>    
>>> +static void update_rps(struct intel_engine_cs *engine)
>>> +{
>>> +     intel_rps_update_engine(engine,
>>> +                             port_request(engine->execlists.port)->ctx);
>>> +}
>>> +
>>>    static void port_assign(struct execlist_port *port, struct i915_request *rq)
>>>    {
>>>        GEM_BUG_ON(port_isset(port));
>>> @@ -728,6 +737,7 @@ static void guc_dequeue(struct intel_engine_cs *engine)
>>>        execlists->first = rb;
>>>        if (submit) {
>>>                port_assign(port, last);
>>> +             update_rps(engine);
>>>                execlists_set_active(execlists, EXECLISTS_ACTIVE_USER);
>>>                guc_submit(engine);
>>>        }
>>> @@ -757,8 +767,10 @@ static void guc_submission_tasklet(unsigned long data)
>>>    
>>>                rq = port_request(&port[0]);
>>>        }
>>> -     if (!rq)
>>> +     if (!rq) {
>>>                execlists_clear_active(execlists, EXECLISTS_ACTIVE_USER);
>>> +             intel_rps_update_engine(engine, NULL);
>>> +     }
>>>    
>>>        if (execlists_is_active(execlists, EXECLISTS_ACTIVE_PREEMPT) &&
>>>            intel_read_status_page(engine, I915_GEM_HWS_PREEMPT_INDEX) ==
>>> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
>>> index 3a69b367e565..518f7b3db857 100644
>>> --- a/drivers/gpu/drm/i915/intel_lrc.c
>>> +++ b/drivers/gpu/drm/i915/intel_lrc.c
>>> @@ -138,6 +138,7 @@
>>>    #include "i915_drv.h"
>>>    #include "i915_gem_render_state.h"
>>>    #include "intel_lrc_reg.h"
>>> +#include "intel_gt_pm.h"
>>>    #include "intel_mocs.h"
>>>    
>>>    #define RING_EXECLIST_QFULL         (1 << 0x2)
>>> @@ -535,6 +536,12 @@ static void inject_preempt_context(struct intel_engine_cs *engine)
>>>        execlists_set_active(&engine->execlists, EXECLISTS_ACTIVE_PREEMPT);
>>>    }
>>>    
>>> +static void update_rps(struct intel_engine_cs *engine)
>>> +{
>>> +     intel_rps_update_engine(engine,
>>> +                             port_request(engine->execlists.port)->ctx);
>>> +}
>>> +
>>>    static void execlists_dequeue(struct intel_engine_cs *engine)
>>>    {
>>>        struct intel_engine_execlists * const execlists = &engine->execlists;
>>> @@ -708,6 +715,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
>>>        spin_unlock_irq(&engine->timeline->lock);
>>>    
>>>        if (submit) {
>>> +             update_rps(engine);
>>>                execlists_set_active(execlists, EXECLISTS_ACTIVE_USER);
>>>                execlists_submit_ports(engine);
>>>        }
>>> @@ -982,6 +990,11 @@ static void execlists_submission_tasklet(unsigned long data)
>>>                                          engine->name, port->context_id);
>>>    
>>>                                execlists_port_complete(execlists, port);
>>> +
>>> +                             /* Switch to the next request/context */
>>> +                             rq = port_request(port);
>>> +                             intel_rps_update_engine(engine,
>>> +                                                     rq ? rq->ctx : NULL);
>>>                        } else {
>>>                                port_set(port, port_pack(rq, count));
>>>                        }
>>> @@ -1717,6 +1730,8 @@ static void reset_common_ring(struct intel_engine_cs *engine,
>>>        __unwind_incomplete_requests(engine);
>>>        spin_unlock(&engine->timeline->lock);
>>>    
>>> +     intel_rps_update_engine(engine, NULL);
>>> +
>>>        /* Mark all CS interrupts as complete */
>>>        execlists->active = 0;
>>>    
>>> diff --git a/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h b/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h
>>> index 9a48aa441743..85b6e6d020b7 100644
>>> --- a/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h
>>> +++ b/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h
>>> @@ -14,6 +14,7 @@ selftest(fence, i915_sw_fence_mock_selftests)
>>>    selftest(scatterlist, scatterlist_mock_selftests)
>>>    selftest(syncmap, i915_syncmap_mock_selftests)
>>>    selftest(uncore, intel_uncore_mock_selftests)
>>> +selftest(gt_pm, intel_gt_pm_mock_selftests)
>>>    selftest(breadcrumbs, intel_breadcrumbs_mock_selftests)
>>>    selftest(timelines, i915_gem_timeline_mock_selftests)
>>>    selftest(requests, i915_request_mock_selftests)
>>> diff --git a/drivers/gpu/drm/i915/selftests/intel_gt_pm.c b/drivers/gpu/drm/i915/selftests/intel_gt_pm.c
>>> new file mode 100644
>>> index 000000000000..c3871eb9eabb
>>> --- /dev/null
>>> +++ b/drivers/gpu/drm/i915/selftests/intel_gt_pm.c
>>> @@ -0,0 +1,130 @@
>>> +/*
>>> + * SPDX-License-Identifier: MIT
>>> + *
>>> + * Copyright © 2018 Intel Corporation
>>> + */
>>> +
>>> +#include "../i915_selftest.h"
>>> +#include "i915_random.h"
>>> +
>>> +#include "mock_gem_device.h"
>>> +
>>> +static void mock_rps_init(struct drm_i915_private *i915)
>>> +{
>>> +     struct intel_rps *rps = &i915->gt_pm.rps;
>>> +
>>> +     /* Disable the register writes */
>>> +     mkwrite_device_info(i915)->gen = 0;
>>> +     mkwrite_device_info(i915)->has_rps = true;
>>> +
>>> +     intel_rps_init(rps);
>>> +
>>> +     rps->min_freq_hw = 0;
>>> +     rps->max_freq_hw = 255;
>>> +
>>> +     rps->min_freq_user = rps->min_freq_hw;
>>> +     rps->max_freq_user = rps->max_freq_hw;
>>> +
>>> +     intel_rps_init__frequencies(rps);
>>> +}
>>> +
>>> +static void mock_rps_fini(struct drm_i915_private *i915)
>>> +{
>>> +     struct intel_rps *rps = &i915->gt_pm.rps;
>>> +
>>> +     cancel_work_sync(&rps->work);
>>> +}
>>> +
>>> +static int igt_rps_engine(void *arg)
>>> +{
>>> +     struct drm_i915_private *i915 = arg;
>>> +     struct intel_rps *rps = &i915->gt_pm.rps;
>>> +     I915_RND_STATE(prng);
>>> +     int err;
>>> +     int i;
>>> +
>>> +     intel_gt_pm_busy(i915); /* Activate RPS */
>>> +
>>> +     /*
>>> +      * Minimum unit tests for intel_rps_update_engine().
>>> +      *
>>> +      * Whenever we call intel_rps_update_engine, it will
>>> +      * replace the context min/max frequency request for a particular
>>> +      * engine and then recompute the global max(min)/min(max) over all
>>> +      * engines. In this mockup, we are limited to checking those
>>> +      * max(min)/min(max) calculations and then seeing if the rps
>>> +      * worker uses those bounds.
>>> +      */
>>> +
>>> +     for (i = 0; i < 256 * 256; i++) {
>>> +             u8 freq = prandom_u32_state(&prng);
>>> +
>>> +             __rps_update_engine(rps, 0, freq, freq);
>>> +             if (rps->min_freq_context != freq ||
>>> +                 rps->max_freq_context != freq) {
>>> +                     pr_err("Context min/max frequencies not restricted to %d, found [%d, %d]\n",
>>> +                            freq, rps->min_freq_context, rps->max_freq_context);
>>> +                     err = -EINVAL;
>>> +                     goto out;
>>> +             }
>>> +             flush_work(&rps->work);
>>> +
>>> +             if (rps->freq != freq) {
>>> +                     pr_err("Tried to restrict frequency to %d, found %d\n",
>>> +                            freq, rps->freq);
>>> +                     err = -EINVAL;
>>> +                     goto out;
>>> +             }
>>> +     }
>>> +
>>> +     __rps_update_engine(rps, 0, rps->min_freq_hw, rps->max_freq_hw);
>>> +     if (rps->min_freq_context != rps->min_freq_hw ||
>>> +         rps->max_freq_context != rps->max_freq_hw) {
>>> +             pr_err("Context frequency not restored to [%d, %d], found [%d, %d]\n",
>>> +                    rps->min_freq_hw, rps->min_freq_hw,
>>> +                    rps->min_freq_context, rps->max_freq_context);
>>> +             err = -EINVAL;
>>> +             goto out;
>>> +     }
>>> +
>>> +     for (i = 0; i < I915_NUM_ENGINES; i++)
>>> +             __rps_update_engine(rps, i, i, 255 - i);
>>> +     i--;
>>> +     if (rps->min_freq_context != i) {
>>> +             pr_err("Minimum context frequency across all engines not raised to %d, found %d\n", i, rps->min_freq_context);
>>> +             err = -EINVAL;
>>> +             goto out;
>>> +     }
>>> +     if (rps->max_freq_context != 255 - i) {
>>> +             pr_err("Maxmimum context frequency across all engines not lowered to %d, found %d\n", 255 - i, rps->max_freq_context);
>>> +             err = -EINVAL;
>>> +             goto out;
>>> +     }
>>> +
>>> +     err = 0;
>>> +out:
>>> +     intel_gt_pm_idle(i915);
>>> +     return err;
>>> +}
>>> +
>>> +int intel_gt_pm_mock_selftests(void)
>>> +{
>>> +     static const struct i915_subtest tests[] = {
>>> +             SUBTEST(igt_rps_engine),
>>> +     };
>>> +     struct drm_i915_private *i915;
>>> +     int err;
>>> +
>>> +     i915 = mock_gem_device();
>>> +     if (!i915)
>>> +             return -ENOMEM;
>>> +
>>> +     mock_rps_init(i915);
>>> +
>>> +     err = i915_subtests(tests, i915);
>>> +
>>> +     mock_rps_fini(i915);
>>> +     drm_dev_unref(&i915->drm);
>>> +
>>> +     return err;
>>> +}
>>> diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
>>> index 7f5634ce8e88..64c6377df769 100644
>>> --- a/include/uapi/drm/i915_drm.h
>>> +++ b/include/uapi/drm/i915_drm.h
>>> @@ -1456,6 +1456,26 @@ struct drm_i915_gem_context_param {
>>>    #define   I915_CONTEXT_MAX_USER_PRIORITY    1023 /* inclusive */
>>>    #define   I915_CONTEXT_DEFAULT_PRIORITY             0
>>>    #define   I915_CONTEXT_MIN_USER_PRIORITY    -1023 /* inclusive */
>>> +
>>> +/*
>>> + * I915_CONTEXT_PARAM_FREQUENCY:
>>> + *
>>> + * Request that when this context runs, the GPU is restricted to run
>>> + * in this frequency range; but still contrained by the global user
>>> + * restriction specified via sysfs.
>>> + *
>>> + * The minimum / maximum frequencies are specified in MHz. Each context
>>> + * starts in the default unrestricted state, where the range is taken from
>>> + * the hardware, and so may be queried.
>>> + *
>>> + * Note the frequency is only changed on a context switch; if the
>>> + * context's frequency is updated whilst the context is currently executing
>>> + * the request will not take effect until the next time the context is run.
>>> + */
>>> +#define I915_CONTEXT_PARAM_FREQUENCY 0x7
>>> +#define   I915_CONTEXT_MIN_FREQUENCY(x) ((x) & 0xffffffff)
>>> +#define   I915_CONTEXT_MAX_FREQUENCY(x) ((x) >> 32)
>>> +#define   I915_CONTEXT_SET_FREQUENCY(min, max) ((__u64)(max) << 32 | (min))
>>>        __u64 value;
>>>    };
>>>    
>>
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