On 25.06.2021 00:41, Matthew Brost wrote: > On Thu, Jun 24, 2021 at 07:02:18PM +0200, Michal Wajdeczko wrote: >> >> >> On 24.06.2021 17:49, Matthew Brost wrote: >>> On Thu, Jun 24, 2021 at 04:48:32PM +0200, Michal Wajdeczko wrote: >>>> >>>> >>>> On 24.06.2021 09:04, Matthew Brost wrote: >>>>> Add non blocking CTB send function, intel_guc_send_nb. GuC submission >>>>> will send CTBs in the critical path and does not need to wait for these >>>>> CTBs to complete before moving on, hence the need for this new function. >>>>> >>>>> The non-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 a 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 | 77 +++++++++++++++++++++-- >>>>> drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h | 3 +- >>>>> 3 files changed, 82 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 4abc59f6f3cd..24b1df6ad4ae 100644 >>>>> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc.h >>>>> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc.h >>>>> @@ -74,7 +74,15 @@ 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) >>>> >>>> hmm, this flag really belongs to intel_guc_ct_send() so it should be >>>> defined as CTB flag near that function declaration >>>> >>> >>> I can move this up a few lines. >>> >>>>> +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 >>>>> @@ -82,7 +90,7 @@ 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 a17215920e58..c9a65d05911f 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" >>>>> @@ -373,7 +378,7 @@ static void write_barrier(struct intel_guc_ct *ct) >>>>> 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; >>>>> @@ -421,9 +426,13 @@ 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])); >>>> >>>> or as we already switched to accept and return whole HXG messages in >>>> guc_send_mmio() maybe we should do the same for CTB variant too and >>>> instead of using extra flag just let caller to prepare proper HXG header >>>> with HXG_EVENT type and then in CTB code just look at this type to make >>>> decision which code path to use >>>> >>> >>> Not sure I follow. Anyways could this be done in a follow up by you if >>> want this change. >>> >>>> note that existing callers should not be impacted, as full HXG header >>>> for the REQUEST message looks exactly the same as "action" code alone. >>>> >>>>> >>>>> CT_DEBUG(ct, "writing (tail %u) %*ph %*ph %*ph\n", >>>>> tail, 4, &header, 4, &hxg, 4 * (len - 1), &action[1]); >>>>> @@ -498,6 +507,46 @@ static int wait_for_ct_request_update(struct ct_request *req, u32 *status) >>>>> return err; >>>>> } >>>>> >>>>> +static inline bool h2g_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; >>>> >>>> here you are returning true(1) as has room >>>> >>> >>> See below. >>> >>>>> +} >>>>> + >>>>> +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 = h2g_has_room(ctb, len + 1); >>>> >>>> but here you treat "1" it as en error >>>> >>> >>> Yes, this patch is broken but fixed in a follow up one. Regardless I'll >>> fix this patch in place. >>> >>>> and this "1" is GUC_HXG_MSG_MIN_LEN, right ? >>>> >>> >>> Not exactly. This is following how ct_send() uses the action + len >>> field. Action[0] field goes in the HXG header and extra + 1 is for the >>> CT header. >> >> well, "len" already counts "action" so by treating input as full HXG >> message (including HXG header) will make it cleaner >> > > Yes, I know. See above. To me GUC_HXG_MSG_MIN_LEN makes zero sense and > it is worse than adding + 1. This + 1 accounts for the CT header not the > HXG header. If any we add a new define, GUC_CT_HDR_LEN, and add that. you mean GUC_CTB_MSG_MIN_LEN ? it's already there [1] [1] https://cgit.freedesktop.org/drm/drm-tip/tree/drivers/gpu/drm/i915/gt/uc/abi/guc_communication_ctb_abi.h#n82 > > Matt > >> we can try do it later but by doing it right now we would avoid >> introducing this send_nb() function and deprecating them long term again >> >>> >>>>> + 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, >>>>> @@ -505,6 +554,7 @@ 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; >>>>> @@ -514,8 +564,20 @@ 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(); >>>>> >>>>> + /* >>>>> + * 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. >>>> >>>> shouldn't we at least try to log such cases with RATE_LIMITED to find >>>> out how "rare" it is, or if really unlikely just return -EBUSY as in >>>> case of non-blocking send ? >>>> >>> >>> Definitely not return -EBUSY as this a blocking call. Perhaps we can log >> >> blocking calls still can fail for various reasons, full CTB is one of >> them, and if we return error (now broken) for non-blocking variant then >> we should do the same for blocking variant as well and let the caller >> decide about next steps >> >>> this, but IGTs likely can hit rather easily. It really is only >>> interesting if real workloads hit this. Regardless that can be a follow >>> up. >> >> if we hide retry in a silent loop then we will not find it out if we hit >> this condition (IGT or real WL) or not >> >>> >>> Matt >>> >>>>> + */ >>>>> +retry: >>>>> spin_lock_irqsave(&ct->ctbs.send.lock, flags); >>>>> + if (unlikely(!h2g_has_room(ctb, len + 1))) { >>>>> + spin_unlock_irqrestore(&ct->ctbs.send.lock, flags); >>>>> + cond_resched(); >>>>> + goto retry; >>>>> + } >>>>> >>>>> fence = ct_get_next_fence(ct); >>>>> request.fence = fence; >>>>> @@ -527,7 +589,7 @@ 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); >>>>> >>>>> @@ -569,7 +631,7 @@ 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; >>>>> @@ -579,6 +641,9 @@ 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..eb69263324ba 100644 >>>>> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h >>>>> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h >>>>> @@ -42,7 +42,6 @@ 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 >>>>> @@ -88,7 +87,7 @@ 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_ */ >>>>>