Re: [PATCH 1/7] drm/i915: Record GT workarounds in a list

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 03/12/2018 11:54, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2018-12-03 11:46:11)
>> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>
>> To enable later verification of GT workaround state at various stages of
>> driver lifetime, we record the list of applicable ones per platforms to a
>> list, from which they are also applied.
>>
>> The added data structure is a simple array of register, mask and value
>> items, which is allocated on demand as workarounds are added to the list.
>>
>> This is a temporary implementation which later in the series gets fused
>> with the existing per context workaround list handling. It is separated at
>> this stage since the following patch fixes a bug which needs to be as easy
>> to backport as possible.
>>
>> Also, since in the following patch we will be adding a new class of
>> workarounds (per engine) which can be applied from interrupt context, we
>> straight away make the provision for safe read-modify-write cycle.
>>
>> v2:
>>   * Change dev_priv to i915 along the init path. (Chris Wilson)
>>   * API rename. (Chris Wilson)
>>
>> v3:
>>   * Remove explicit list size tracking in favour of growing the allocation
>>     in power of two chunks. (Chris Wilson)
>>
>> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> # v2
>> ---
>>   drivers/gpu/drm/i915/i915_drv.c          |   1 +
>>   drivers/gpu/drm/i915/i915_drv.h          |   2 +
>>   drivers/gpu/drm/i915/i915_gem.c          |   4 +-
>>   drivers/gpu/drm/i915/intel_workarounds.c | 491 +++++++++++++++--------
>>   drivers/gpu/drm/i915/intel_workarounds.h |  23 +-
>>   5 files changed, 353 insertions(+), 168 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
>> index e39016713464..ee5116b62cd2 100644
>> --- a/drivers/gpu/drm/i915/i915_drv.c
>> +++ b/drivers/gpu/drm/i915/i915_drv.c
>> @@ -1453,6 +1453,7 @@ static int i915_driver_init_hw(struct drm_i915_private *dev_priv)
>>   
>>          intel_uncore_sanitize(dev_priv);
>>   
>> +       intel_gt_init_workarounds(dev_priv);
>>          i915_gem_load_init_fences(dev_priv);
>>   
>>          /* On the 945G/GM, the chipset reports the MSI capability on the
>> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
>> index 43ac6873a2bb..9ddbcc1f3554 100644
>> --- a/drivers/gpu/drm/i915/i915_drv.h
>> +++ b/drivers/gpu/drm/i915/i915_drv.h
>> @@ -69,6 +69,7 @@
>>   #include "intel_ringbuffer.h"
>>   #include "intel_uncore.h"
>>   #include "intel_wopcm.h"
>> +#include "intel_workarounds.h"
>>   #include "intel_uc.h"
>>   
>>   #include "i915_gem.h"
>> @@ -1652,6 +1653,7 @@ struct drm_i915_private {
>>          int dpio_phy_iosf_port[I915_NUM_PHYS_VLV];
>>   
>>          struct i915_workarounds workarounds;
>> +       struct i915_wa_list gt_wa_list;
>>   
>>          struct i915_frontbuffer_tracking fb_tracking;
>>   
>> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
>> index c55b1f75c980..6333a7d6af5a 100644
>> --- a/drivers/gpu/drm/i915/i915_gem.c
>> +++ b/drivers/gpu/drm/i915/i915_gem.c
>> @@ -5334,7 +5334,7 @@ int i915_gem_init_hw(struct drm_i915_private *dev_priv)
>>                  I915_WRITE(MI_PREDICATE_RESULT_2, IS_HSW_GT3(dev_priv) ?
>>                             LOWER_SLICE_ENABLED : LOWER_SLICE_DISABLED);
>>   
>> -       intel_gt_workarounds_apply(dev_priv);
>> +       intel_gt_apply_workarounds(dev_priv);
>>   
>>          i915_gem_init_swizzling(dev_priv);
>>   
>> @@ -5706,6 +5706,8 @@ void i915_gem_fini(struct drm_i915_private *dev_priv)
>>          i915_gem_contexts_fini(dev_priv);
>>          mutex_unlock(&dev_priv->drm.struct_mutex);
>>   
>> +       intel_wa_list_free(&dev_priv->gt_wa_list);
>> +
>>          intel_cleanup_gt_powersave(dev_priv);
>>   
>>          intel_uc_fini_misc(dev_priv);
>> diff --git a/drivers/gpu/drm/i915/intel_workarounds.c b/drivers/gpu/drm/i915/intel_workarounds.c
>> index e5cd6c6c66c3..f05f13547034 100644
>> --- a/drivers/gpu/drm/i915/intel_workarounds.c
>> +++ b/drivers/gpu/drm/i915/intel_workarounds.c
>> @@ -48,6 +48,18 @@
>>    * - Public functions to init or apply the given workaround type.
>>    */
>>   
>> +static void wa_init_start(struct i915_wa_list *wal, const char *name)
>> +{
>> +       wal->name = name;
>> +}
>> +
>> +static void wa_init_finish(struct i915_wa_list *wal)
>> +{
>> +       if (wal->count)
>> +               DRM_DEBUG_DRIVER("Initialized %u %s workarounds\n",
>> +                                wal->count, wal->name);
> 
> Does this become if (!wal->count) return; later?

Done.

>> +}
>> +
>>   static void wa_add(struct drm_i915_private *i915,
>>                     i915_reg_t reg, const u32 mask, const u32 val)
>>   {
>> @@ -575,160 +587,240 @@ int intel_ctx_workarounds_emit(struct i915_request *rq)
>>          return 0;
>>   }
>>   
>> -static void bdw_gt_workarounds_apply(struct drm_i915_private *dev_priv)
>> +static void
>> +wal_add(struct i915_wa_list *wal, const struct i915_wa *wa)
>> +{
>> +       const unsigned int grow = 1 << 4;
>> +
>> +       GEM_BUG_ON(!is_power_of_2(grow));
>> +
>> +       if (IS_ALIGNED(wal->count, grow)) { /* Either uninitialized or full. */
> 
> Neat.
> 
>> +               struct i915_wa *list;
>> +
>> +               list = kcalloc(ALIGN(wal->count + 1, grow), sizeof(*wa),
>> +                              GFP_KERNEL);
> 
> (Quietly comments on the calloc here ;)

Oh I don't want to complicate things with zeroing the tail. Or you 
wouldn't bother with zeroing at all since I always copy over used 
entries? So unused, who cares about them?

> 
>> +               if (!list) {
>> +                       DRM_ERROR("No space for workaround init!\n");
>> +                       return;
>> +               }
>> +
>> +               if (wal->list)
>> +                       memcpy(list, wal->list, sizeof(*wa) * wal->count);
>> +
>> +               wal->list = list;
>> +       }
>> +
>> +       memcpy(&wal->list[wal->count], wa, sizeof(*wa));
>> +       wal->count++;
> 
> I'd push for
> 	wal->list[wal->count++] = wa;
> Might as well use static type checking.

Ok.

>> +struct i915_wa_list {
>> +       const char      *name;
>> +       unsigned int    count;
>> +       struct i915_wa  *list;
> 
> Oh well, didn't save anything after all.

How nothing, one unsigned int per wa_list instance! :)

Regards,

Tvrtko

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