Re: [PATCH 04/11] drm/i915: Support for GuC interrupts

Goel, Akash
2016-06-28T11:12:50Z

On 6/28/2016 3:33 PM, Tvrtko Ursulin wrote:
>
> On 27/06/16 13:16, akash.goel@intel.com wrote:
>> From: Sagar Arun Kamble <sagar.a.kamble@intel.com>
>>
>> There are certain types of interrupts which Host can recieve from GuC.
>> GuC ukernel sends an interrupt to Host for certain events, like for
>> example retrieve/consume the logs generated by ukernel.
>> This patch adds support to receive interrupts from GuC but currently
>> enables & partially handles only the interrupt sent by GuC ukernel.
>> Future patches will add support for handling other interrupt types.
>>
>> v2: Use common low level routines for PM IER/IIR programming (Chris)
>> Rename interrupt functions to gen9_xxx from gen8_xxx (Chris)
>> Replace disabling of wake ref asserts with rpm get/put (Chris)
>>
>> Signed-off-by: Sagar Arun Kamble <sagar.a.kamble@intel.com>
>> Signed-off-by: Akash Goel <akash.goel@intel.com>
>> ---
>> drivers/gpu/drm/i915/i915_drv.h | 1 +
>> drivers/gpu/drm/i915/i915_guc_submission.c | 5 ++
>> drivers/gpu/drm/i915/i915_irq.c | 95
>> ++++++++++++++++++++++++++++--
>> drivers/gpu/drm/i915/i915_reg.h | 11 ++++
>> drivers/gpu/drm/i915/intel_drv.h | 3 +
>> drivers/gpu/drm/i915/intel_guc.h | 5 ++
>> drivers/gpu/drm/i915/intel_guc_loader.c | 4 ++
>> 7 files changed, 120 insertions(+), 4 deletions(-)
>>>>
>> +static void gen9_guc2host_events_work(struct work_struct *work)
>> +{
>> + struct drm_i915_private *dev_priv =
>> + container_of(work, struct drm_i915_private, guc.events_work);
>> +
>> + spin_lock_irq(&dev_priv->irq_lock);
>> + /* Speed up work cancelation during disabling guc interrupts. */
>> + if (!dev_priv->guc.interrupts_enabled) {
>> + spin_unlock_irq(&dev_priv->irq_lock);
>> + return;
>> + }
>> +
>> + /* Though this work item gets synced during rpm suspend, but
>> still need
>> + * a rpm get/put to avoid the warning, as it could get executed in a
>> + * window, where rpm ref count has dropped to zero but rpm
>> suspend has
>> + * not kicked in. Generally device is expected to be active only
>> at this
>> + * time so get/put should be really quick.
>> + */
>> + intel_runtime_pm_get(dev_priv);
>> +
>> + gen6_enable_pm_irq(dev_priv, GEN9_GUC_TO_HOST_INT_EVENT);
>> + spin_unlock_irq(&dev_priv->irq_lock);
>> +
>> + /* TODO: Handle the events for which GuC interrupted host */
>> +
>> + intel_runtime_pm_put(dev_priv);
>> +}
>>
>> /**
>> * ivybridge_parity_work - Workqueue called when a parity error
>> interrupt
>> @@ -1371,11 +1435,13 @@ static irqreturn_t gen8_gt_irq_ack(struct
>> drm_i915_private *dev_priv,
>> DRM_ERROR("The master control interrupt lied (GT3)!\n");
>> }
>>
>> - if (master_ctl & GEN8_GT_PM_IRQ) {
>> + if (master_ctl & (GEN8_GT_PM_IRQ | GEN8_GT_GUC_IRQ)) {
>> gt_iir[2] = I915_READ_FW(GEN8_GT_IIR(2));
>> - if (gt_iir[2] & dev_priv->pm_rps_events) {
>> + if (gt_iir[2] & (dev_priv->pm_rps_events |
>> + dev_priv->guc_events)) {
>> I915_WRITE_FW(GEN8_GT_IIR(2),
>> - gt_iir[2] & dev_priv->pm_rps_events);
>> + gt_iir[2] & (dev_priv->pm_rps_events |
>> + dev_priv->guc_events));
>> ret = IRQ_HANDLED;
>> } else
>> DRM_ERROR("The master control interrupt lied (PM)!\n");
>> @@ -1407,6 +1473,9 @@ static void gen8_gt_irq_handler(struct
>> drm_i915_private *dev_priv,
>>
>> if (gt_iir[2] & dev_priv->pm_rps_events)
>> gen6_rps_irq_handler(dev_priv, gt_iir[2]);
>> +
>> + if (gt_iir[2] & dev_priv->guc_events)
>> + gen9_guc_irq_handler(dev_priv, gt_iir[2]);
>> }
>>
>> static bool bxt_port_hotplug_long_detect(enum port port, u32 val)
>> @@ -1653,6 +1722,20 @@ static void gen6_rps_irq_handler(struct
>> drm_i915_private *dev_priv, u32 pm_iir)
>> }
>> }
>>
>> +static void gen9_guc_irq_handler(struct drm_i915_private *dev_priv,
>> u32 gt_iir)
>> +{
>> + if (gt_iir & GEN9_GUC_TO_HOST_INT_EVENT) {
>> + spin_lock(&dev_priv->irq_lock);
>> + if (dev_priv->guc.interrupts_enabled) {
>
> So it is expected interrupts will always be enabled when
> i915.guc_log_level is set, correct?
>
Yes currently only when guc_log_level > 0, interrupt should be enabled.

But we need to disable/enable the interrupt upon suspend/resume and
across GPU reset.
So interrupt may not be always in a enabled state when guc_log_level>0.

> Also do you need to check against dev_priv->guc.interrupts_enabled at
> all then? Or from an opposite angle, would you instead need to log the
> fact unexpected interrupt was received here?

I think this check is needed, to avoid the race in disabling interrupt.
Please refer the sequence in interrupt disabling function (same as rps
disabling), there we first set the interrupts_enabled flag to false,
then wait for the work item to finish execution and then program the IMR
register.

>
>> + /* Process all the GuC to Host events in bottom half */
>> + gen6_disable_pm_irq(dev_priv,
>> + GEN9_GUC_TO_HOST_INT_EVENT);
>
> Why it is important to disable the interrupt here? Not for the queue
> work I think.

We want to & can handle one interrupt at a time, unless the queued work
item is executed we can't process the next interrupt, so better to keep
the interrupt masked.
Sorry this is what is my understanding.

>
> Also, is it safe with regards to potentially losing the interrupt?
>
Particularly for the FLUSH_LOG_BUFFER case, GuC won't send a new flush
interrupt unless its gets an acknowledgement (flush signal) of the
previous one from Host.

>> + queue_work(dev_priv->wq, &dev_priv->guc.events_work);
>
> Because dev_priv->wq is a one a time in order wq so if something else is
> running on it and taking time, can that also be a cause of dropping an
> interrupt or being late with sending the flush signal to the guc and so
> losing some logs?

Its a Driver's private workqueue and Turbo work item is also queued
inside this workqueue which too needs to be executed without much delay.
But yes the flush work item can get substantially delayed in case if
there are other work items queued before it, especially the
mm.retire_work (but generally executes every ~1 second).

Best would be if the log buffer (44KB data) can be sampled in IRQ
context (or Tasklet context) itself.

Best regards
Akash
>
>> + }
>> + spin_unlock(&dev_priv->irq_lock);
>> + }
>> +}
>> +
>> static bool intel_pipe_handle_vblank(struct drm_i915_private *dev_priv,
>> enum pipe pipe)
>> {
>> @@ -3809,7 +3892,7 @@ static void gen8_gt_irq_postinstall(struct
>> drm_i915_private *dev_priv)
>> GEN8_IRQ_INIT_NDX(GT, 1, ~gt_interrupts[1], gt_interrupts[1]);
>> /*
>> * RPS interrupts will get enabled/disabled on demand when RPS
>> itself
>> - * is enabled/disabled.
>> + * is enabled/disabled. Same wil be the case for GuC interrupts.
>> */
>> GEN8_IRQ_INIT_NDX(GT, 2, dev_priv->pm_irq_mask, 0);
>> GEN8_IRQ_INIT_NDX(GT, 3, ~gt_interrupts[3], gt_interrupts[3]);
>> @@ -4594,6 +4677,10 @@ void intel_irq_init(struct drm_i915_private
>> *dev_priv)
>>
>> INIT_WORK(&dev_priv->rps.work, gen6_pm_rps_work);
>> INIT_WORK(&dev_priv->l3_parity.error_work, ivybridge_parity_work);
>> + INIT_WORK(&dev_priv->guc.events_work, gen9_guc2host_events_work);
>> +
>> + if (HAS_GUC_UCODE(dev))
>> + dev_priv->guc_events = GEN9_GUC_TO_HOST_INT_EVENT;
>>
>> /* Let's track the enabled rps events */
>> if (IS_VALLEYVIEW(dev_priv))
>> diff --git a/drivers/gpu/drm/i915/i915_reg.h
>> b/drivers/gpu/drm/i915/i915_reg.h
>> index c6bfbf8..4441918 100644
>> --- a/drivers/gpu/drm/i915/i915_reg.h
>> +++ b/drivers/gpu/drm/i915/i915_reg.h
>> @@ -5963,6 +5963,7 @@ enum {
>> #define GEN8_DE_PIPE_A_IRQ (1<<16)
>> #define GEN8_DE_PIPE_IRQ(pipe) (1<<(16+(pipe)))
>> #define GEN8_GT_VECS_IRQ (1<<6)
>> +#define GEN8_GT_GUC_IRQ (1<<5)
>> #define GEN8_GT_PM_IRQ (1<<4)
>> #define GEN8_GT_VCS2_IRQ (1<<3)
>> #define GEN8_GT_VCS1_IRQ (1<<2)
>> @@ -5974,6 +5975,16 @@ enum {
>> #define GEN8_GT_IIR(which) _MMIO(0x44308 + (0x10 * (which)))
>> #define GEN8_GT_IER(which) _MMIO(0x4430c + (0x10 * (which)))
>>
>> +#define GEN9_GUC_TO_HOST_INT_EVENT (1<<31)
>> +#define GEN9_GUC_EXEC_ERROR_EVENT (1<<30)
>> +#define GEN9_GUC_DISPLAY_EVENT (1<<29)
>> +#define GEN9_GUC_SEMA_SIGNAL_EVENT (1<<28)
>> +#define GEN9_GUC_IOMMU_MSG_EVENT (1<<27)
>> +#define GEN9_GUC_DB_RING_EVENT (1<<26)
>> +#define GEN9_GUC_DMA_DONE_EVENT (1<<25)
>> +#define GEN9_GUC_FATAL_ERROR_EVENT (1<<24)
>> +#define GEN9_GUC_NOTIFICATION_EVENT (1<<23)
>> +
>> #define GEN8_RCS_IRQ_SHIFT 0
>> #define GEN8_BCS_IRQ_SHIFT 16
>> #define GEN8_VCS1_IRQ_SHIFT 0
>> diff --git a/drivers/gpu/drm/i915/intel_drv.h
>> b/drivers/gpu/drm/i915/intel_drv.h
>> index 2a013fc..6966ffe 100644
>> --- a/drivers/gpu/drm/i915/intel_drv.h
>> +++ b/drivers/gpu/drm/i915/intel_drv.h
>> @@ -1083,6 +1083,9 @@ void gen8_irq_power_well_post_enable(struct
>> drm_i915_private *dev_priv,
>> unsigned int pipe_mask);
>> void gen8_irq_power_well_pre_disable(struct drm_i915_private *dev_priv,
>> unsigned int pipe_mask);
>> +void gen9_reset_guc_interrupts(struct drm_i915_private *dev_priv);
>> +void gen9_enable_guc_interrupts(struct drm_i915_private *dev_priv);
>> +void gen9_disable_guc_interrupts(struct drm_i915_private *dev_priv);
>>
>> /* intel_crt.c */
>> void intel_crt_init(struct drm_device *dev);
>> diff --git a/drivers/gpu/drm/i915/intel_guc.h
>> b/drivers/gpu/drm/i915/intel_guc.h
>> index 3e3e743..ae787e2 100644
>> --- a/drivers/gpu/drm/i915/intel_guc.h
>> +++ b/drivers/gpu/drm/i915/intel_guc.h
>> @@ -126,6 +126,11 @@ struct intel_guc {
>> struct intel_guc_fw guc_fw;
>> uint32_t log_flags;
>> struct drm_i915_gem_object *log_obj;
>> + /*
>> + * work, interrupts_enabled are protected by dev_priv->irq_lock
>> + */
>> + struct work_struct events_work;
>> + bool interrupts_enabled;
>>
>> struct drm_i915_gem_object *ads_obj;
>>
>> diff --git a/drivers/gpu/drm/i915/intel_guc_loader.c
>> b/drivers/gpu/drm/i915/intel_guc_loader.c
>> index db3c897..fcf36a2 100644
>> --- a/drivers/gpu/drm/i915/intel_guc_loader.c
>> +++ b/drivers/gpu/drm/i915/intel_guc_loader.c
>> @@ -448,6 +448,7 @@ int intel_guc_setup(struct drm_device *dev)
>> }
>>
>> direct_interrupts_to_host(dev_priv);
>> + gen9_reset_guc_interrupts(dev_priv);
>>
>> guc_fw->guc_fw_load_status = GUC_FIRMWARE_PENDING;
>>
>> @@ -494,6 +495,9 @@ int intel_guc_setup(struct drm_device *dev)
>> intel_guc_fw_status_repr(guc_fw->guc_fw_load_status));
>>
>> if (i915.enable_guc_submission) {
>> + if (i915.guc_log_level >= 0)
>> + gen9_enable_guc_interrupts(dev_priv);
>> +
>> err = i915_guc_submission_enable(dev_priv);
>> if (err)
>> goto fail;
>>
>
> Regards,
>
> Tvrtko