Re: [RFC PATCH 18/97] drm/i915/guc: Don't receive all G2H messages in irq handler

On Thu, May 06, 2021 at 12:13:32PM -0700, Matthew Brost wrote:

From: Michal Wajdeczko michal.wajdeczko@intel.com

In irq handler try to receive just single G2H message, let other messages to be received from tasklet.

Signed-off-by: Michal Wajdeczko michal.wajdeczko@intel.com Signed-off-by: Matthew Brost matthew.brost@intel.com

---

drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c | 67 ++++++++++++++++------- drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h | 3 + 2 files changed, 50 insertions(+), 20 deletions(-)

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 cb58fa7f970c..d630ec32decf 100644 --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c @@ -81,6 +81,7 @@ enum { CTB_SEND = 0, CTB_RECV = 1 };

enum { CTB_OWNER_HOST = 0 };

+static void ct_receive_tasklet_func(unsigned long data); static void ct_incoming_request_worker_func(struct work_struct *w);

/** @@ -95,6 +96,7 @@ void intel_guc_ct_init_early(struct intel_guc_ct *ct) INIT_LIST_HEAD(&ct->requests.pending); INIT_LIST_HEAD(&ct->requests.incoming); INIT_WORK(&ct->requests.worker, ct_incoming_request_worker_func);

• tasklet_init(&ct->receive_tasklet, ct_receive_tasklet_func, (unsigned long)ct);

This function is deprecated. tasklet_setup should be used. I can fix this up when I post the CTB patches.

}

static inline const char *guc_ct_buffer_type_to_str(u32 type) @@ -244,6 +246,7 @@ void intel_guc_ct_fini(struct intel_guc_ct *ct) { GEM_BUG_ON(ct->enabled);

• tasklet_kill(&ct->receive_tasklet); i915_vma_unpin_and_release(&ct->vma, I915_VMA_RELEASE_MAP); memset(ct, 0, sizeof(*ct));

} @@ -629,7 +632,7 @@ static int ct_read(struct intel_guc_ct *ct, u32 *data) CT_DEBUG(ct, "received %*ph\n", 4 * len, data);

desc->head = head * 4;

• return 0;

• return available - len;

corrupted: CT_ERROR(ct, "Corrupted descriptor addr=%#x head=%u tail=%u size=%u\n", @@ -665,10 +668,10 @@ static int ct_handle_response(struct intel_guc_ct *ct, const u32 *msg) u32 status; u32 datalen; struct ct_request *req;

• unsigned long flags; bool found = false;

  GEM_BUG_ON(!ct_header_is_response(header));

• GEM_BUG_ON(!in_irq());

  /* Response payload shall at least include fence and status */ if (unlikely(len < 2)) {

@@ -688,7 +691,7 @@ static int ct_handle_response(struct intel_guc_ct *ct, const u32 *msg)

CT_DEBUG(ct, "response fence %u status %#x\n", fence, status);

• spin_lock(&ct->requests.lock);

• spin_lock_irqsave(&ct->requests.lock, flags); list_for_each_entry(req, &ct->requests.pending, link) { if (unlikely(fence != req->fence)) { CT_DEBUG(ct, "request %u awaits response\n",

@@ -707,7 +710,7 @@ static int ct_handle_response(struct intel_guc_ct *ct, const u32 *msg) found = true; break; }

• spin_unlock(&ct->requests.lock);

• spin_unlock_irqrestore(&ct->requests.lock, flags);

  if (!found) CT_ERROR(ct, "Unsolicited response %*ph\n", msgsize, msg);

@@ -821,31 +824,55 @@ static int ct_handle_request(struct intel_guc_ct *ct, const u32 *msg) return 0; }

+static int ct_receive(struct intel_guc_ct *ct) +{

• u32 msg[GUC_CT_MSG_LEN_MASK + 1]; /* one extra dw for the header */
• unsigned long flags;
• int ret;
• spin_lock_irqsave(&ct->ctbs.recv.lock, flags);
• ret = ct_read(ct, msg);
• spin_unlock_irqrestore(&ct->ctbs.recv.lock, flags);
• if (ret < 0)

• return ret;
  

• if (ct_header_is_response(msg[0]))

• ct_handle_response(ct, msg);
  

• else

• ct_handle_request(ct, msg);
  

• return ret;

+}

+static void ct_try_receive_message(struct intel_guc_ct *ct) +{

• int ret;
• if (GEM_WARN_ON(!ct->enabled))

• return;
  

• ret = ct_receive(ct);
• if (ret > 0)

• tasklet_hi_schedule(&ct->receive_tasklet);
  

+}

+static void ct_receive_tasklet_func(unsigned long data) +{

As mentioned above tasklet_init is deprecated. The callback now accepts the tasklet structure and ct can be looked up via container_of macro.

Everything else looks good.

With that and changing to the new tasklet API: Reviewed-by: Matthew Brost matthew.brost@intel.com

• struct intel_guc_ct *ct = (struct intel_guc_ct *)data;
• ct_try_receive_message(ct);

+}

/*

• When we're communicating with the GuC over CT, GuC uses events
• to notify us about new messages being posted on the RECV buffer.

*/ void intel_guc_ct_event_handler(struct intel_guc_ct *ct) {

• u32 msg[GUC_CT_MSG_LEN_MASK + 1]; /* one extra dw for the header */

• unsigned long flags;

• int err = 0;

• if (unlikely(!ct->enabled)) { WARN(1, "Unexpected GuC event received while CT disabled!\n"); return; }

• do {

• spin_lock_irqsave(&ct->ctbs.recv.lock, flags);
  

• err = ct_read(ct, msg);
  

• spin_unlock_irqrestore(&ct->ctbs.recv.lock, flags);
  

• if (err)
  

• 	break;
  

• if (ct_header_is_response(msg[0]))
  

• 	err = ct_handle_response(ct, msg);
  

• else
  

• 	err = ct_handle_request(ct, msg);
  

• } while (!err);

• ct_try_receive_message(ct);

} 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 bc52dc479a14..cb222f202301 100644 --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h @@ -6,6 +6,7 @@ #ifndef _INTEL_GUC_CT_H_ #define _INTEL_GUC_CT_H_

+#include <linux/interrupt.h> #include <linux/spinlock.h> #include <linux/workqueue.h>

@@ -55,6 +56,8 @@ struct intel_guc_ct { struct intel_guc_ct_buffer recv; } ctbs;

• struct tasklet_struct receive_tasklet;
• struct { u32 last_fence; /* last fence used to send request */

-- 2.28.0