Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
> Quoting Mika Kuoppala (2019-02-28 16:14:11)
>> We have an exported function for stopping the engine before
>> disabling a ringbuffer. Take it into use.
>>
>> v2: use fw on empty check
>> v3: tail is tail
>>
>> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
>> Signed-off-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
>> Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
>> ---
>> drivers/gpu/drm/i915/intel_engine_cs.c | 3 ++
>> drivers/gpu/drm/i915/intel_ringbuffer.c | 41 ++++++++++++++-----------
>> 2 files changed, 26 insertions(+), 18 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
>> index df8f88142f1d..e35dc0386bf6 100644
>> --- a/drivers/gpu/drm/i915/intel_engine_cs.c
>> +++ b/drivers/gpu/drm/i915/intel_engine_cs.c
>> @@ -856,6 +856,9 @@ void intel_engine_cancel_stop_cs(struct intel_engine_cs *engine)
>> {
>> struct drm_i915_private *dev_priv = engine->i915;
>>
>> + if (INTEL_GEN(dev_priv) < 3)
>> + return;
>> +
>> GEM_TRACE("%s\n", engine->name);
>>
>> I915_WRITE_FW(RING_MI_MODE(engine->mmio_base),
>> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
>> index 1b96b0960adc..5fe28d9087b7 100644
>> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
>> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
>> @@ -604,26 +604,32 @@ static void ring_setup_status_page(struct intel_engine_cs *engine)
>> flush_cs_tlb(engine);
>> }
>>
>> +static bool ring_is_empty(struct intel_engine_cs *engine)
>> +{
>> + struct drm_i915_private *dev_priv = engine->i915;
>> + const u32 base = engine->mmio_base;
>> +
>> + return (I915_READ_FW(RING_HEAD(base)) & HEAD_ADDR) ==
>> + (I915_READ_FW(RING_TAIL(base)) & TAIL_ADDR);
>> +}
>> +
>> static bool stop_ring(struct intel_engine_cs *engine)
>> {
>> struct drm_i915_private *dev_priv = engine->i915;
>> + int ret;
>>
>> - if (INTEL_GEN(dev_priv) > 2) {
>> - I915_WRITE_MODE(engine, _MASKED_BIT_ENABLE(STOP_RING));
>> - if (intel_wait_for_register(dev_priv,
>> - RING_MI_MODE(engine->mmio_base),
>> - MODE_IDLE,
>> - MODE_IDLE,
>> - 1000)) {
>> - DRM_ERROR("%s : timed out trying to stop ring\n",
>> - engine->name);
>> - /* Sometimes we observe that the idle flag is not
>> - * set even though the ring is empty. So double
>> - * check before giving up.
>> - */
>> - if (I915_READ_HEAD(engine) != I915_READ_TAIL(engine))
>> - return false;
>> - }
>> + ret = intel_engine_stop_cs(engine);
>> + if (ret == -ENODEV)
>> + ret = 0;
>> +
>> + if (ret) {
>> + /*
>> + * Sometimes we observe that the idle flag is not
>> + * set even though the ring is empty. So double
>> + * check before giving up.
>> + */
>> + if (!ring_is_empty(engine))
>> + return false;
>
> Hmm, thinking more about this, shouldn't we push this down to stop_cs()?
>
> If that's reporting an error in a situation where we can determine that
> the ring is idle anyway, we can report the stop_cs succeeded.
Makes sense, I will take a look.
I felt small urge to deflate the 'stop'.
Would it be confusing if we just did
intel_engine_start|stop instead of stop_cs and
cancel_stop_cs?
So hmm:
intel_engine_start()
intel_engine_stop()
these would only toggle the STOP_RING
and for replacing stop_ring with:
intel_engine_empty_ring()
for zeroing the heads.
one 'stop' to rule the (ring)world!?
-Mika
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