From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-14.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,HK_RANDOM_FROM,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 67E3DC4707F for ; Tue, 25 May 2021 09:21:09 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0CF4761421 for ; Tue, 25 May 2021 09:21:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0CF4761421 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 2FA2C6E9CF; Tue, 25 May 2021 09:21:08 +0000 (UTC) Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by gabe.freedesktop.org (Postfix) with ESMTPS id C26326E9CF; Tue, 25 May 2021 09:21:05 +0000 (UTC) IronPort-SDR: ecDs2vrtqfOSctbOVVvJl5odvXL6w1dbu4qNrWz8shsEs1POxKMobbzAZyGwf2b8ycx5ywbCGQ eRWKs316RJsw== X-IronPort-AV: E=McAfee;i="6200,9189,9994"; a="223313722" X-IronPort-AV: E=Sophos;i="5.82,328,1613462400"; d="scan'208";a="223313722" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 May 2021 02:21:05 -0700 IronPort-SDR: 5Hd/yEtoBMLZcFFy8g4D0FX0cYn0j/8uGL+ujkBdvHTcPi6A8h6sVwP9M+ZEBbLL11/7V65cqR ZlqlkmUR3fzA== X-IronPort-AV: E=Sophos;i="5.82,328,1613462400"; d="scan'208";a="442460682" Received: from tomeara-mobl.ger.corp.intel.com (HELO [10.213.211.66]) ([10.213.211.66]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 May 2021 02:21:03 -0700 Subject: Re: [Intel-gfx] [RFC PATCH 36/97] drm/i915/guc: Add non blocking CTB send function To: Matthew Brost , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org References: <20210506191451.77768-1-matthew.brost@intel.com> <20210506191451.77768-37-matthew.brost@intel.com> From: Tvrtko Ursulin Organization: Intel Corporation UK Plc Message-ID: <375b4de4-168f-9c4c-dbb8-f42fd6303628@linux.intel.com> Date: Tue, 25 May 2021 10:21:00 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210506191451.77768-37-matthew.brost@intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: jason.ekstrand@intel.com, daniel.vetter@intel.com Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" 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? > > 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 > Signed-off-by: Matthew Brost > --- > 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 > +#include > +#include > +#include > + > #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? > + } 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? > > + /* > + * 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? > > 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 > #include > #include > +#include > > #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. > }; > > 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