drm/amdgpu: fix race between pstate and remote buffer map

Vega20 arbitrates pstate at hive level and not device level. Last peer to
remote buffer unmap could drop P-State while another process is still
remote buffer mapped.

With this fix, P-States still needs to be disabled for now as SMU bug
was discovered on synchronous P2P transfers.  This should be fixed in the
next FW update.
Signed-off-by: Jonathan Kim <Jonathan.Kim@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu.h

@@ -986,8 +986,6 @@ struct amdgpu_device {
 	uint64_t			unique_id;
 	uint64_t	df_perfmon_config_assign_mask[AMDGPU_MAX_DF_PERFMONS];
 
-	/* device pstate */
-	int				pstate;
 	/* enable runtime pm on the device */
 	bool                            runpm;
 	bool                            in_runpm;

drivers/gpu/drm/amd/amdgpu/amdgpu_device.c

@@ -2248,7 +2248,8 @@ static int amdgpu_device_ip_late_init(struct amdgpu_device *adev)
 				if (gpu_instance->adev->flags & AMD_IS_APU)
 					continue;
 
-				r = amdgpu_xgmi_set_pstate(gpu_instance->adev, 0);
+				r = amdgpu_xgmi_set_pstate(gpu_instance->adev,
+						AMDGPU_XGMI_PSTATE_MIN);
 				if (r) {
 					DRM_ERROR("pstate setting failed (%d).\n", r);
 					break;

drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c

@@ -2124,11 +2124,8 @@ struct amdgpu_bo_va *amdgpu_vm_bo_add(struct amdgpu_device *adev,
 	if (bo && amdgpu_xgmi_same_hive(adev, amdgpu_ttm_adev(bo->tbo.bdev)) &&
 	    (bo->preferred_domains & AMDGPU_GEM_DOMAIN_VRAM)) {
 		bo_va->is_xgmi = true;
-		mutex_lock(&adev->vm_manager.lock_pstate);
 		/* Power up XGMI if it can be potentially used */
-		if (++adev->vm_manager.xgmi_map_counter == 1)
-			amdgpu_xgmi_set_pstate(adev, 1);
-		mutex_unlock(&adev->vm_manager.lock_pstate);
+		amdgpu_xgmi_set_pstate(adev, AMDGPU_XGMI_PSTATE_MAX_VEGA20);
 	}
 
 	return bo_va;
@@ -2551,12 +2548,8 @@ void amdgpu_vm_bo_rmv(struct amdgpu_device *adev,
 
 	dma_fence_put(bo_va->last_pt_update);
 
-	if (bo && bo_va->is_xgmi) {
-		mutex_lock(&adev->vm_manager.lock_pstate);
-		if (--adev->vm_manager.xgmi_map_counter == 0)
-			amdgpu_xgmi_set_pstate(adev, 0);
-		mutex_unlock(&adev->vm_manager.lock_pstate);
-	}
+	if (bo && bo_va->is_xgmi)
+		amdgpu_xgmi_set_pstate(adev, AMDGPU_XGMI_PSTATE_MIN);
 
 	kfree(bo_va);
 }
@@ -3166,9 +3159,6 @@ void amdgpu_vm_manager_init(struct amdgpu_device *adev)
 
 	idr_init(&adev->vm_manager.pasid_idr);
 	spin_lock_init(&adev->vm_manager.pasid_lock);
-
-	adev->vm_manager.xgmi_map_counter = 0;
-	mutex_init(&adev->vm_manager.lock_pstate);
 }
 
 /**

drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h

@@ -349,10 +349,6 @@ struct amdgpu_vm_manager {
 	 */
 	struct idr				pasid_idr;
 	spinlock_t				pasid_lock;
-
-	/* counter of mapped memory through xgmi */
-	uint32_t				xgmi_map_counter;
-	struct mutex				lock_pstate;
 };
 
 #define amdgpu_vm_copy_pte(adev, ib, pe, src, count) ((adev)->vm_manager.vm_pte_funcs->copy_pte((ib), (pe), (src), (count)))

drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.c

@@ -373,7 +373,13 @@ struct amdgpu_hive_info *amdgpu_get_xgmi_hive(struct amdgpu_device *adev, int lo
 
 	if (lock)
 		mutex_lock(&tmp->hive_lock);
-	tmp->pstate = -1;
+	tmp->pstate = AMDGPU_XGMI_PSTATE_UNKNOWN;
+	tmp->hi_req_gpu = NULL;
+	/*
+	 * hive pstate on boot is high in vega20 so we have to go to low
+	 * pstate on after boot.
+	 */
+	tmp->hi_req_count = AMDGPU_MAX_XGMI_DEVICE_PER_HIVE;
 	mutex_unlock(&xgmi_mutex);
 
 	return tmp;
@@ -383,50 +389,51 @@ int amdgpu_xgmi_set_pstate(struct amdgpu_device *adev, int pstate)
 {
 	int ret = 0;
 	struct amdgpu_hive_info *hive = amdgpu_get_xgmi_hive(adev, 0);
-	struct amdgpu_device *tmp_adev;
-	bool update_hive_pstate = true;
-	bool is_high_pstate = pstate && adev->asic_type == CHIP_VEGA20;
+	struct amdgpu_device *request_adev = hive->hi_req_gpu ?
+						hive->hi_req_gpu : adev;
+	bool is_hi_req = pstate == AMDGPU_XGMI_PSTATE_MAX_VEGA20;
+	bool init_low = hive->pstate == AMDGPU_XGMI_PSTATE_UNKNOWN;
 
-	if (!hive)
+	/* fw bug so temporarily disable pstate switching */
+	if (!hive || adev->asic_type == CHIP_VEGA20)
 		return 0;
 
 	mutex_lock(&hive->hive_lock);
 
-	if (hive->pstate == pstate) {
-		adev->pstate = is_high_pstate ? pstate : adev->pstate;
+	if (is_hi_req)
+		hive->hi_req_count++;
+	else
+		hive->hi_req_count--;
+
+	/*
+	 * Vega20 only needs single peer to request pstate high for the hive to
+	 * go high but all peers must request pstate low for the hive to go low
+	 */
+	if (hive->pstate == pstate ||
+			(!is_hi_req && hive->hi_req_count && !init_low))
 		goto out;
-	}
 
-	dev_dbg(adev->dev, "Set xgmi pstate %d.\n", pstate);
+	dev_dbg(request_adev->dev, "Set xgmi pstate %d.\n", pstate);
 
-	ret = amdgpu_dpm_set_xgmi_pstate(adev, pstate);
+	ret = amdgpu_dpm_set_xgmi_pstate(request_adev, pstate);
 	if (ret) {
-		dev_err(adev->dev,
+		dev_err(request_adev->dev,
 			"XGMI: Set pstate failure on device %llx, hive %llx, ret %d",
-			adev->gmc.xgmi.node_id,
-			adev->gmc.xgmi.hive_id, ret);
+			request_adev->gmc.xgmi.node_id,
+			request_adev->gmc.xgmi.hive_id, ret);
 		goto out;
 	}
 
-	/* Update device pstate */
-	adev->pstate = pstate;
-
-	/*
-	 * Update the hive pstate only all devices of the hive
-	 * are in the same pstate
-	 */
-	list_for_each_entry(tmp_adev, &hive->device_list, gmc.xgmi.head) {
-		if (tmp_adev->pstate != adev->pstate) {
-			update_hive_pstate = false;
-			break;
-		}
-	}
-	if (update_hive_pstate || is_high_pstate)
+	if (init_low)
+		hive->pstate = hive->hi_req_count ?
+					hive->pstate : AMDGPU_XGMI_PSTATE_MIN;
+	else {
 		hive->pstate = pstate;
-
+		hive->hi_req_gpu = pstate != AMDGPU_XGMI_PSTATE_MIN ?
+							adev : NULL;
+	}
 out:
 	mutex_unlock(&hive->hive_lock);
-
 	return ret;
 }
 
@@ -507,9 +514,6 @@ int amdgpu_xgmi_add_device(struct amdgpu_device *adev)
 		goto exit;
 	}
 
-	/* Set default device pstate */
-	adev->pstate = -1;
-
 	top_info = &adev->psp.xgmi_context.top_info;
 
 	list_add_tail(&adev->gmc.xgmi.head, &hive->device_list);

drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.h

@@ -25,6 +25,7 @@
 #include <drm/task_barrier.h>
 #include "amdgpu_psp.h"
 
+
 struct amdgpu_hive_info {
 	uint64_t		hive_id;
 	struct list_head	device_list;
@@ -33,8 +34,14 @@ struct amdgpu_hive_info {
 	struct kobject *kobj;
 	struct device_attribute dev_attr;
 	struct amdgpu_device *adev;
-	int pstate; /*0 -- low , 1 -- high , -1 unknown*/
+	int hi_req_count;
+	struct amdgpu_device *hi_req_gpu;
 	struct task_barrier tb;
+	enum {
+		AMDGPU_XGMI_PSTATE_MIN,
+		AMDGPU_XGMI_PSTATE_MAX_VEGA20,
+		AMDGPU_XGMI_PSTATE_UNKNOWN
+	} pstate;
 };
 
 struct amdgpu_pcs_ras_field {