Re: [PATCH v5] drm/i915/icl: Enhanced execution list support

Daniele Ceraolo Spurio
2018-01-19T16:15:04Z

On 19/01/18 05:05, Mika Kuoppala wrote:
> Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com> writes:
>
>> From: Thomas Daniel <thomas.daniel@intel.com>
>>
>> Enhanced Execlists is an upgraded version of execlists which supports
>> up to 8 ports. The lrcs to be submitted are written to a submit queue,
>> which is then loaded on the HW. When writing to the ELSP register, the
>> lrcs are written cyclically in the queue from position 0 to position 7.
>> Alternatively, it is possible to write directly in the individual
>> positions of the queue using the ELSQ registers. To be able to re-use
>> all the existing code we're using the latter method and we're currently
>> limiting ourself to only using 2 elements.
>>
>> The preemption flow is sligthly different with enhanced execlists, so
>> this patch turns preemption off temporarily for Gen11+ while we wait for
>> the new mechanism to land.
>>
>> v2: Rebase.
>> v3: Switch from !IS_GEN11 to GEN < 11 (Daniele Ceraolo Spurio).
>> v4: Use the elsq registers instead of elsp. (Daniele Ceraolo Spurio)
>> v5: Reword commit, rename regs to be closer to specs, turn off
>> preemption (Daniele), reuse engine->execlists.elsp (Chris)
>>
>> Cc: Chris Wilson <chris@chris-wilson.co.uk>
>> Signed-off-by: Thomas Daniel <thomas.daniel@intel.com>
>> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
>> Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
>
> Was going to adopt this patch from Rodrigo but you were faster.
>
> I choose to stash the elsq and use it as a gen11 vs rest toggle:
>
> Relevant bits:
>
> +static inline void write_port(struct intel_engine_execlists * const execlists,
> + unsigned int n,
> + u64 desc)
> +{
> + if (execlists->elsq)
> + gen11_elsq_write(desc, n, execlists->elsq);
> + else
> + gen8_elsp_write(desc, execlists->elsp);
> +}
> +
> +static inline void submit_ports(struct intel_engine_execlists * const execlists)
> +{
> + /* for gen11+ we need to manually load the submit queue */
> + if (execlists->elsq) {
> + struct intel_engine_cs *engine =
> + container_of(execlists,
> + struct intel_engine_cs,
> + execlists);
> + struct drm_i915_private *dev_priv = engine->i915;
> +
> + I915_WRITE_FW(RING_ELCR(engine), ELCR_LOAD);
> + }
> +}
> +
>

I was undecided about hiding the code in sub-functions because of the
pre-emption path. There is no need in gen11 to inject a context to
preempt to idle, so the inject_preempt function will be pre-gen11 only
and therefore I'd prefer to keep a direct call to elsp_write there. IMHO
it'd be cleaner to have similar code in both places, hence the
open-coding. This said, I'd be happy to change it like you proposed if
there is a general preference to abstract things a bit in the shared
path even if the pre-emption path stays different.

Regarding using execlists->elsq as a toggle, I was thinking that we
could have a device info flag instead, so we could use it even before
setting execlists->elsq. Any preference on this?

Thanks,
Daniele

P.S. If you want to take over feel free to send an updated patch ;)

> ...
> -Mika
>
>> ---
>> drivers/gpu/drm/i915/i915_drv.h | 5 ++++-
>> drivers/gpu/drm/i915/intel_lrc.c | 35 ++++++++++++++++++++++++++++-----
>> drivers/gpu/drm/i915/intel_lrc.h | 3 +++
>> drivers/gpu/drm/i915/intel_ringbuffer.h | 6 ++++--
>> 4 files changed, 41 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
>> index c42015b..3163543 100644
>> --- a/drivers/gpu/drm/i915/i915_drv.h
>> +++ b/drivers/gpu/drm/i915/i915_drv.h
>> @@ -2738,8 +2738,11 @@ static inline unsigned int i915_sg_segment_size(void)
>>
>> #define HAS_LOGICAL_RING_CONTEXTS(dev_priv) \
>> ((dev_priv)->info.has_logical_ring_contexts)
>> +
>> +/* XXX: Preemption disabled for Gen11+ until support for new flow lands */
>> #define HAS_LOGICAL_RING_PREEMPTION(dev_priv) \
>> - ((dev_priv)->info.has_logical_ring_preemption)
>> + ((dev_priv)->info.has_logical_ring_preemption && \
>> + INTEL_GEN(dev_priv) < 11)
>>
>> #define HAS_EXECLISTS(dev_priv) HAS_LOGICAL_RING_CONTEXTS(dev_priv)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
>> index ff25f20..67ad7c9 100644
>> --- a/drivers/gpu/drm/i915/intel_lrc.c
>> +++ b/drivers/gpu/drm/i915/intel_lrc.c
>> @@ -428,11 +428,24 @@ static inline void elsp_write(u64 desc, u32 __iomem *elsp)
>> writel(lower_32_bits(desc), elsp);
>> }
>>
>> +static inline void elsqc_write(u64 desc, u32 __iomem *elsqc, u32 port)
>> +{
>> + writel(lower_32_bits(desc), elsqc + port * 2);
>> + writel(upper_32_bits(desc), elsqc + port * 2 + 1);
>> +}
>> +
>> static void execlists_submit_ports(struct intel_engine_cs *engine)
>> {
>> + struct drm_i915_private *dev_priv = engine->i915;
>> struct execlist_port *port = engine->execlists.port;
>> unsigned int n;
>>
>> + /*
>> + * Gen11+ note: the submit queue is not cleared after being submitted
>> + * to the HW so we need to make sure we always clean it up. This is
>> + * currently ensured by the fact that we always write the same number
>> + * of elsq entries, keep this in mind before changing the loop below.
>> + */
>> for (n = execlists_num_ports(&engine->execlists); n--; ) {
>> struct drm_i915_gem_request *rq;
>> unsigned int count;
>> @@ -456,8 +469,16 @@ static void execlists_submit_ports(struct intel_engine_cs *engine)
>> desc = 0;
>> }
>>
>> - elsp_write(desc, engine->execlists.elsp);
>> + if (INTEL_GEN(dev_priv) >= 11)
>> + elsqc_write(desc, engine->execlists.els, n);
>> + else
>> + elsp_write(desc, engine->execlists.els);
>> }
>> +
>> + /* for gen11+ we need to manually load the submit queue */
>> + if (INTEL_GEN(dev_priv) >= 11)
>> + I915_WRITE_FW(RING_EXECLIST_CONTROL(engine), EL_CTRL_LOAD);
>> +
>> execlists_clear_active(&engine->execlists, EXECLISTS_ACTIVE_HWACK);
>> }
>>
>> @@ -506,9 +527,9 @@ static void inject_preempt_context(struct intel_engine_cs *engine)
>>
>> GEM_TRACE("%s\n", engine->name);
>> for (n = execlists_num_ports(&engine->execlists); --n; )
>> - elsp_write(0, engine->execlists.elsp);
>> + elsp_write(0, engine->execlists.els);
>>
>> - elsp_write(ce->lrc_desc, engine->execlists.elsp);
>> + elsp_write(ce->lrc_desc, engine->execlists.els);
>> execlists_clear_active(&engine->execlists, EXECLISTS_ACTIVE_HWACK);
>> }
>>
>> @@ -2016,8 +2037,12 @@ static int logical_ring_init(struct intel_engine_cs *engine)
>> if (ret)
>> goto error;
>>
>> - engine->execlists.elsp =
>> - engine->i915->regs + i915_mmio_reg_offset(RING_ELSP(engine));
>> + if (INTEL_GEN(engine->i915) >= 11)
>> + engine->execlists.els = engine->i915->regs +
>> + i915_mmio_reg_offset(RING_EXECLIST_SQ_CONTENTS(engine));
>> + else
>> + engine->execlists.els = engine->i915->regs +
>> + i915_mmio_reg_offset(RING_ELSP(engine));
>>
>> return 0;
>>
>> diff --git a/drivers/gpu/drm/i915/intel_lrc.h b/drivers/gpu/drm/i915/intel_lrc.h
>> index 6d4f9b9..3ab4266 100644
>> --- a/drivers/gpu/drm/i915/intel_lrc.h
>> +++ b/drivers/gpu/drm/i915/intel_lrc.h
>> @@ -38,6 +38,9 @@
>> #define CTX_CTRL_ENGINE_CTX_RESTORE_INHIBIT (1 << 0)
>> #define CTX_CTRL_RS_CTX_ENABLE (1 << 1)
>> #define RING_CONTEXT_STATUS_BUF_BASE(engine) _MMIO((engine)->mmio_base + 0x370)
>> +#define RING_EXECLIST_SQ_CONTENTS(engine) _MMIO((engine)->mmio_base + 0x510)
>> +#define RING_EXECLIST_CONTROL(engine) _MMIO((engine)->mmio_base + 0x550)
>> +#define EL_CTRL_LOAD (1 << 0)
>> #define RING_CONTEXT_STATUS_BUF_LO(engine, i) _MMIO((engine)->mmio_base + 0x370 + (i) * 8)
>> #define RING_CONTEXT_STATUS_BUF_HI(engine, i) _MMIO((engine)->mmio_base + 0x370 + (i) * 8 + 4)
>> #define RING_CONTEXT_STATUS_PTR(engine) _MMIO((engine)->mmio_base + 0x3a0)
>> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
>> index c5ff203..d36bb73 100644
>> --- a/drivers/gpu/drm/i915/intel_ringbuffer.h
>> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
>> @@ -200,9 +200,11 @@ struct intel_engine_execlists {
>> bool no_priolist;
>>
>> /**
>> - * @elsp: the ExecList Submission Port register
>> + * @els: gen-specific execlist submission register
>> + * set to the ExecList Submission Port (elsp) register pre-Gen11 and to
>> + * the ExecList Submission Queue Contents register array for Gen11+
>> */
>> - u32 __iomem *elsp;
>> + u32 __iomem *els;
>>
>> /**
>> * @port: execlist port states
>> --
>> 1.9.1
>>
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