On Tue, May 25, 2021 at 10:21:00AM +0100, Tvrtko Ursulin wrote: > > On 06/05/2021 20:13, Matthew Brost wrote: > > Add non blocking CTB send function, intel_guc_send_nb. In order to > > support a non blocking CTB send function a spin lock is needed to > > protect the CTB descriptors fields. Also the non blocking call must not > > update the fence value as this value is owned by the blocking call > > (intel_guc_send). > > Could the commit message say why the non-blocking send function is needed? > Sure. Something like: 'CTBs will be used in the critical patch of GuC submission and there is no need to wait for each CTB complete before moving on the i915' > > > > The blocking CTB now must have a flow control mechanism to ensure the > > buffer isn't overrun. A lazy spin wait is used as we believe the flow > > control condition should be rare with properly sized buffer. > > > > The function, intel_guc_send_nb, is exported in this patch but unused. > > Several patches later in the series make use of this function. > > > > Signed-off-by: John Harrison <John.C.Harrison@xxxxxxxxx> > > Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx> > > --- > > drivers/gpu/drm/i915/gt/uc/intel_guc.h | 12 ++- > > drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c | 96 +++++++++++++++++++++-- > > drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h | 7 +- > > 3 files changed, 105 insertions(+), 10 deletions(-) > > > > diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc.h b/drivers/gpu/drm/i915/gt/uc/intel_guc.h > > index c20f3839de12..4c0a367e41d8 100644 > > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc.h > > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc.h > > @@ -75,7 +75,15 @@ static inline struct intel_guc *log_to_guc(struct intel_guc_log *log) > > static > > inline int intel_guc_send(struct intel_guc *guc, const u32 *action, u32 len) > > { > > - return intel_guc_ct_send(&guc->ct, action, len, NULL, 0); > > + return intel_guc_ct_send(&guc->ct, action, len, NULL, 0, 0); > > +} > > + > > +#define INTEL_GUC_SEND_NB BIT(31) > > +static > > +inline int intel_guc_send_nb(struct intel_guc *guc, const u32 *action, u32 len) > > +{ > > + return intel_guc_ct_send(&guc->ct, action, len, NULL, 0, > > + INTEL_GUC_SEND_NB); > > } > > static inline int > > @@ -83,7 +91,7 @@ intel_guc_send_and_receive(struct intel_guc *guc, const u32 *action, u32 len, > > u32 *response_buf, u32 response_buf_size) > > { > > return intel_guc_ct_send(&guc->ct, action, len, > > - response_buf, response_buf_size); > > + response_buf, response_buf_size, 0); > > } > > static inline void intel_guc_to_host_event_handler(struct intel_guc *guc) > > diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c > > index a76603537fa8..af7314d45a78 100644 > > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c > > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c > > @@ -3,6 +3,11 @@ > > * Copyright © 2016-2019 Intel Corporation > > */ > > +#include <linux/circ_buf.h> > > +#include <linux/ktime.h> > > +#include <linux/time64.h> > > +#include <linux/timekeeping.h> > > + > > #include "i915_drv.h" > > #include "intel_guc_ct.h" > > #include "gt/intel_gt.h" > > @@ -308,6 +313,7 @@ int intel_guc_ct_enable(struct intel_guc_ct *ct) > > if (unlikely(err)) > > goto err_deregister; > > + ct->requests.last_fence = 1; > > ct->enabled = true; > > return 0; > > @@ -343,10 +349,22 @@ static u32 ct_get_next_fence(struct intel_guc_ct *ct) > > return ++ct->requests.last_fence; > > } > > +static void write_barrier(struct intel_guc_ct *ct) { > > + struct intel_guc *guc = ct_to_guc(ct); > > + struct intel_gt *gt = guc_to_gt(guc); > > + > > + if (i915_gem_object_is_lmem(guc->ct.vma->obj)) { > > + GEM_BUG_ON(guc->send_regs.fw_domains); > > + intel_uncore_write_fw(gt->uncore, GEN11_SOFT_SCRATCH(0), 0); > > It's safe to write to this reg? Does it need a comment to explain it? > Yes, it is same. IMO 'SCRATCH' in the name is enough documentation. > > + } else { > > + wmb(); > > + } > > +} > > + > > static int ct_write(struct intel_guc_ct *ct, > > const u32 *action, > > u32 len /* in dwords */, > > - u32 fence) > > + u32 fence, u32 flags) > > { > > struct intel_guc_ct_buffer *ctb = &ct->ctbs.send; > > struct guc_ct_buffer_desc *desc = ctb->desc; > > @@ -393,9 +411,13 @@ static int ct_write(struct intel_guc_ct *ct, > > FIELD_PREP(GUC_CTB_MSG_0_NUM_DWORDS, len) | > > FIELD_PREP(GUC_CTB_MSG_0_FENCE, fence); > > - hxg = FIELD_PREP(GUC_HXG_MSG_0_TYPE, GUC_HXG_TYPE_REQUEST) | > > - FIELD_PREP(GUC_HXG_REQUEST_MSG_0_ACTION | > > - GUC_HXG_REQUEST_MSG_0_DATA0, action[0]); > > + hxg = (flags & INTEL_GUC_SEND_NB) ? > > + (FIELD_PREP(GUC_HXG_MSG_0_TYPE, GUC_HXG_TYPE_EVENT) | > > + FIELD_PREP(GUC_HXG_EVENT_MSG_0_ACTION | > > + GUC_HXG_EVENT_MSG_0_DATA0, action[0])) : > > + (FIELD_PREP(GUC_HXG_MSG_0_TYPE, GUC_HXG_TYPE_REQUEST) | > > + FIELD_PREP(GUC_HXG_REQUEST_MSG_0_ACTION | > > + GUC_HXG_REQUEST_MSG_0_DATA0, action[0])); > > CT_DEBUG(ct, "writing (tail %u) %*ph %*ph %*ph\n", > > tail, 4, &header, 4, &hxg, 4 * (len - 1), &action[1]); > > @@ -412,6 +434,12 @@ static int ct_write(struct intel_guc_ct *ct, > > } > > GEM_BUG_ON(tail > size); > > + /* > > + * make sure H2G buffer update and LRC tail update (if this triggering a > > + * submission) are visable before updating the descriptor tail > > + */ > > + write_barrier(ct); > > + > > /* now update descriptor */ > > WRITE_ONCE(desc->tail, tail); > > @@ -466,6 +494,46 @@ static int wait_for_ct_request_update(struct ct_request *req, u32 *status) > > return err; > > } > > +static inline bool ctb_has_room(struct intel_guc_ct_buffer *ctb, u32 len_dw) > > +{ > > + struct guc_ct_buffer_desc *desc = ctb->desc; > > + u32 head = READ_ONCE(desc->head); > > + u32 space; > > + > > + space = CIRC_SPACE(desc->tail, head, ctb->size); > > + > > + return space >= len_dw; > > +} > > + > > +static int ct_send_nb(struct intel_guc_ct *ct, > > + const u32 *action, > > + u32 len, > > + u32 flags) > > +{ > > + struct intel_guc_ct_buffer *ctb = &ct->ctbs.send; > > + unsigned long spin_flags; > > + u32 fence; > > + int ret; > > + > > + spin_lock_irqsave(&ctb->lock, spin_flags); > > + > > + ret = ctb_has_room(ctb, len + 1); > > + if (unlikely(ret)) > > + goto out; > > + > > + fence = ct_get_next_fence(ct); > > + ret = ct_write(ct, action, len, fence, flags); > > + if (unlikely(ret)) > > + goto out; > > + > > + intel_guc_notify(ct_to_guc(ct)); > > + > > +out: > > + spin_unlock_irqrestore(&ctb->lock, spin_flags); > > + > > + return ret; > > +} > > + > > static int ct_send(struct intel_guc_ct *ct, > > const u32 *action, > > u32 len, > > @@ -473,6 +541,7 @@ static int ct_send(struct intel_guc_ct *ct, > > u32 response_buf_size, > > u32 *status) > > { > > + struct intel_guc_ct_buffer *ctb = &ct->ctbs.send; > > struct ct_request request; > > unsigned long flags; > > u32 fence; > > @@ -482,8 +551,20 @@ static int ct_send(struct intel_guc_ct *ct, > > GEM_BUG_ON(!len); > > GEM_BUG_ON(len & ~GUC_CT_MSG_LEN_MASK); > > GEM_BUG_ON(!response_buf && response_buf_size); > > + might_sleep(); > > Sleep is just cond_resched below or there is more? > Yes, the cond_resched. > > + /* > > + * We use a lazy spin wait loop here as we believe that if the CT > > + * buffers are sized correctly the flow control condition should be > > + * rare. > > + */ > > +retry: > > spin_lock_irqsave(&ct->ctbs.send.lock, flags); > > + if (unlikely(!ctb_has_room(ctb, len + 1))) { > > + spin_unlock_irqrestore(&ct->ctbs.send.lock, flags); > > + cond_resched(); > > + goto retry; > > + } > > If this patch is about adding a non-blocking send function, and below we can > see that it creates a fork: > > intel_guc_ct_send: > ... > if (flags & INTEL_GUC_SEND_NB) > return ct_send_nb(ct, action, len, flags); > > ret = ct_send(ct, action, len, response_buf, response_buf_size, &status); > > Then why is there a change in ct_send here, which is not the new > non-blocking path? > There is not a change to ct_send(), just to intel_guc_ct_send. As for why intel_guc_ct_send is updated and we don't just a new public function, this was another reviewers suggestion. Again can't make everyone happy. > > fence = ct_get_next_fence(ct); > > request.fence = fence; > > @@ -495,7 +576,7 @@ static int ct_send(struct intel_guc_ct *ct, > > list_add_tail(&request.link, &ct->requests.pending); > > spin_unlock(&ct->requests.lock); > > - err = ct_write(ct, action, len, fence); > > + err = ct_write(ct, action, len, fence, 0); > > spin_unlock_irqrestore(&ct->ctbs.send.lock, flags); > > @@ -537,7 +618,7 @@ static int ct_send(struct intel_guc_ct *ct, > > * Command Transport (CT) buffer based GuC send function. > > */ > > int intel_guc_ct_send(struct intel_guc_ct *ct, const u32 *action, u32 len, > > - u32 *response_buf, u32 response_buf_size) > > + u32 *response_buf, u32 response_buf_size, u32 flags) > > { > > u32 status = ~0; /* undefined */ > > int ret; > > @@ -547,6 +628,9 @@ int intel_guc_ct_send(struct intel_guc_ct *ct, const u32 *action, u32 len, > > return -ENODEV; > > } > > + if (flags & INTEL_GUC_SEND_NB) > > + return ct_send_nb(ct, action, len, flags); > > + > > ret = ct_send(ct, action, len, response_buf, response_buf_size, &status); > > if (unlikely(ret < 0)) { > > CT_ERROR(ct, "Sending action %#x failed (err=%d status=%#X)\n", > > diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h > > index 1ae2dde6db93..55ef7c52472f 100644 > > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h > > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h > > @@ -9,6 +9,7 @@ > > #include <linux/interrupt.h> > > #include <linux/spinlock.h> > > #include <linux/workqueue.h> > > +#include <linux/ktime.h> > > #include "intel_guc_fwif.h" > > @@ -42,7 +43,6 @@ struct intel_guc_ct_buffer { > > bool broken; > > }; > > - > > /** Top-level structure for Command Transport related data > > * > > * Includes a pair of CT buffers for bi-directional communication and tracking > > @@ -69,6 +69,9 @@ struct intel_guc_ct { > > struct list_head incoming; /* incoming requests */ > > struct work_struct worker; /* handler for incoming requests */ > > } requests; > > + > > + /** @stall_time: time of first time a CTB submission is stalled */ > > + ktime_t stall_time; > > Unused in this patch. > Yea, wrong patch. Will fix. Matt > > }; > > void intel_guc_ct_init_early(struct intel_guc_ct *ct); > > @@ -88,7 +91,7 @@ static inline bool intel_guc_ct_enabled(struct intel_guc_ct *ct) > > } > > int intel_guc_ct_send(struct intel_guc_ct *ct, const u32 *action, u32 len, > > - u32 *response_buf, u32 response_buf_size); > > + u32 *response_buf, u32 response_buf_size, u32 flags); > > void intel_guc_ct_event_handler(struct intel_guc_ct *ct); > > #endif /* _INTEL_GUC_CT_H_ */ > > > > Regards, > > Tvrtko