Commit b43b9950 authored by Matthew Brost's avatar Matthew Brost Committed by John Harrison
Browse files

drm/i915/guc: Add stall timer to non blocking CTB send function 



Implement a stall timer which fails H2G CTBs once a period of time
with no forward progress is reached to prevent deadlock.

v2:
 (Michal)
  - Improve error message in ct_deadlock()
  - Set broken when ct_deadlock() returns true
  - Return -EPIPE on ct_deadlock()
v3:
 (Michal)
  - Add ms to stall timer comment
 (Matthew)
  - Move broken check to intel_guc_ct_send()

Signed-off-by: default avatarJohn Harrison <John.C.Harrison@Intel.com>
Signed-off-by: default avatarDaniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: default avatarMatthew Brost <matthew.brost@intel.com>
Reviewed-by: default avatarJohn Harrison <John.C.Harrison@Intel.com>
Signed-off-by: default avatarJohn Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210708162055.129996-6-matthew.brost@intel.com
parent 1681924d

drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c

+55 −7
Original line number Diff line number Diff line
@@ -4,6 +4,9 @@ 
 */



#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"
@@ -316,6 +319,7 @@ int intel_guc_ct_enable(struct intel_guc_ct *ct) 
		goto err_deregister;



	ct->enabled = true;

	ct->stall_time = KTIME_MAX;



	return 0;
@@ -389,9 +393,6 @@ static int ct_write(struct intel_guc_ct *ct, 
	u32 *cmds = ctb->cmds;

	unsigned int i;



	if (unlikely(ctb->broken))

		return -EPIPE;



	if (unlikely(desc->status))

		goto corrupted;
@@ -505,6 +506,25 @@ static int wait_for_ct_request_update(struct ct_request *req, u32 *status) 
	return err;

}



#define GUC_CTB_TIMEOUT_MS	1500

static inline bool ct_deadlocked(struct intel_guc_ct *ct)

{

	long timeout = GUC_CTB_TIMEOUT_MS;

	bool ret = ktime_ms_delta(ktime_get(), ct->stall_time) > timeout;



	if (unlikely(ret)) {

		struct guc_ct_buffer_desc *send = ct->ctbs.send.desc;

		struct guc_ct_buffer_desc *recv = ct->ctbs.send.desc;



		CT_ERROR(ct, "Communication stalled for %lld ms, desc status=%#x,%#x\n",

			 ktime_ms_delta(ktime_get(), ct->stall_time),

			 send->status, recv->status);

		ct->ctbs.send.broken = true;

	}



	return ret;

}



static inline bool h2g_has_room(struct intel_guc_ct_buffer *ctb, u32 len_dw)

{

	struct guc_ct_buffer_desc *desc = ctb->desc;
@@ -516,6 +536,26 @@ static inline bool h2g_has_room(struct intel_guc_ct_buffer *ctb, u32 len_dw) 
	return space >= len_dw;

}



static int has_room_nb(struct intel_guc_ct *ct, u32 len_dw)

{

	struct intel_guc_ct_buffer *ctb = &ct->ctbs.send;



	lockdep_assert_held(&ct->ctbs.send.lock);



	if (unlikely(!h2g_has_room(ctb, len_dw))) {

		if (ct->stall_time == KTIME_MAX)

			ct->stall_time = ktime_get();



		if (unlikely(ct_deadlocked(ct)))

			return -EPIPE;

		else

			return -EBUSY;

	}



	ct->stall_time = KTIME_MAX;

	return 0;

}



static int ct_send_nb(struct intel_guc_ct *ct,

		      const u32 *action,

		      u32 len,
@@ -528,11 +568,9 @@ static int ct_send_nb(struct intel_guc_ct *ct, 


	spin_lock_irqsave(&ctb->lock, spin_flags);



	ret = h2g_has_room(ctb, len + GUC_CTB_HDR_LEN);

	if (unlikely(!ret)) {

		ret = -EBUSY;

	ret = has_room_nb(ct, len + GUC_CTB_HDR_LEN);

	if (unlikely(ret))

		goto out;

	}



	fence = ct_get_next_fence(ct);

	ret = ct_write(ct, action, len, fence, flags);
@@ -575,8 +613,13 @@ static int ct_send(struct intel_guc_ct *ct, 
retry:

	spin_lock_irqsave(&ctb->lock, flags);

	if (unlikely(!h2g_has_room(ctb, len + GUC_CTB_HDR_LEN))) {

		if (ct->stall_time == KTIME_MAX)

			ct->stall_time = ktime_get();

		spin_unlock_irqrestore(&ctb->lock, flags);



		if (unlikely(ct_deadlocked(ct)))

			return -EPIPE;



		if (msleep_interruptible(sleep_period_ms))

			return -EINTR;

		sleep_period_ms = sleep_period_ms << 1;
@@ -584,6 +627,8 @@ static int ct_send(struct intel_guc_ct *ct, 
		goto retry;

	}



	ct->stall_time = KTIME_MAX;



	fence = ct_get_next_fence(ct);

	request.fence = fence;

	request.status = 0;
@@ -646,6 +691,9 @@ int intel_guc_ct_send(struct intel_guc_ct *ct, const u32 *action, u32 len, 
		return -ENODEV;

	}



	if (unlikely(ct->ctbs.send.broken))

		return -EPIPE;



	if (flags & INTEL_GUC_CT_SEND_NB)

		return ct_send_nb(ct, action, len, flags);

drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h

+4 −0
Original line number Diff line number Diff line
@@ -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"
@@ -68,6 +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;

};



void intel_guc_ct_init_early(struct intel_guc_ct *ct);