[Intel-gfx] [RFC 1/1] drm/i915/dgfx: Avoid parent bridge rpm on mmap mappings

[Anshuman Gupta]

As per PCIe Spec Section 5.3,
When a Type 1 Function associated with a Switch/Root
Port (a “virtual bridge”) is in a non-D0 power state,
it will emulate the behavior of a conventional PCI bridge
in its handling of Memory, I/O, and Configuration
Requests and Completions. All Memory and I/O requests
flowing Downstream are terminated as Unsupported Requests.

Due to above limitations when Intel DGFX Cards graphics
PCI func's upstream bridge(referred as VSP) enters to D3,
all mmap memory mapping associated with lmem objects
reads 0xff, therefore avoiding VSP runtime suspend
accordingly.

This will make sure that user can read valid data from lmem,
while DGFX Card graphics PCI func is in D3 state.

Signed-off-by: Anshuman Gupta <anshuman.gupta at intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_mman.c | 11 ++++++++
 drivers/gpu/drm/i915/gem/i915_gem_ttm.c  |  8 ++++++
 drivers/gpu/drm/i915/intel_runtime_pm.c  | 35 ++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_runtime_pm.h  |  2 ++
 4 files changed, 56 insertions(+)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
index 0c5c43852e24..968bed5b56d3 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
@@ -845,6 +845,10 @@ static void vm_open(struct vm_area_struct *vma)
 	struct drm_i915_gem_object *obj = mmo->obj;
 
 	GEM_BUG_ON(!obj);
+
+	if (i915_gem_object_is_lmem(obj))
+		intel_runtime_pm_get_vsp(to_i915(obj->base.dev));
+
 	i915_gem_object_get(obj);
 }
 
@@ -854,6 +858,10 @@ static void vm_close(struct vm_area_struct *vma)
 	struct drm_i915_gem_object *obj = mmo->obj;
 
 	GEM_BUG_ON(!obj);
+
+	if (i915_gem_object_is_lmem(obj))
+		intel_runtime_pm_put_vsp(to_i915(obj->base.dev));
+
 	i915_gem_object_put(obj);
 }
 
@@ -972,6 +980,9 @@ int i915_gem_mmap(struct file *filp, struct vm_area_struct *vma)
 		return PTR_ERR(anon);
 	}
 
+	if (i915_gem_object_is_lmem(obj))
+		intel_runtime_pm_get_vsp(to_i915(obj->base.dev));
+
 	vma->vm_flags |= VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP | VM_IO;
 
 	/*
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
index 5a5cf332d8a5..bcacd95fdbc1 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
@@ -1101,6 +1101,10 @@ static void ttm_vm_open(struct vm_area_struct *vma)
 		i915_ttm_to_gem(vma->vm_private_data);
 
 	GEM_BUG_ON(!obj);
+
+	if (i915_gem_object_is_lmem(obj))
+		intel_runtime_pm_get_vsp(to_i915(obj->base.dev));
+
 	i915_gem_object_get(obj);
 }
 
@@ -1110,6 +1114,10 @@ static void ttm_vm_close(struct vm_area_struct *vma)
 		i915_ttm_to_gem(vma->vm_private_data);
 
 	GEM_BUG_ON(!obj);
+
+	if (i915_gem_object_is_lmem(obj))
+		intel_runtime_pm_put_vsp(to_i915(obj->base.dev));
+
 	i915_gem_object_put(obj);
 }
 
diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
index 6ed5786bcd29..a5557918674f 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -646,3 +646,38 @@ void intel_runtime_pm_init_early(struct intel_runtime_pm *rpm)
 
 	init_intel_runtime_pm_wakeref(rpm);
 }
+
+void intel_runtime_pm_get_vsp(struct drm_i915_private *i915)
+{
+	struct pci_dev *pdev = to_pci_dev(i915->drm.dev), *vsp;
+
+	if (!IS_DGFX(i915))
+		return;
+
+	vsp = pci_upstream_bridge(pdev);
+	if (!vsp) {
+		drm_err(&i915->drm, "Failed to get the PCI upstream bridge\n");
+		return;
+	}
+
+	pci_dbg(vsp, "get runtime usage count\n");
+	pm_runtime_get_sync(&vsp->dev);
+}
+
+void intel_runtime_pm_put_vsp(struct drm_i915_private *i915)
+{
+	struct pci_dev *pdev = to_pci_dev(i915->drm.dev), *vsp;
+
+	if (!IS_DGFX(i915))
+		return;
+
+	vsp = pci_upstream_bridge(pdev);
+	if (!vsp) {
+		drm_err(&i915->drm, "Failed to get the PCI upstream bridge\n");
+		return;
+	}
+
+	pci_dbg(vsp, "put runtime usage count\n");
+	pm_runtime_mark_last_busy(&vsp->dev);
+	pm_runtime_put(&vsp->dev);
+}
diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.h b/drivers/gpu/drm/i915/intel_runtime_pm.h
index d9160e3ff4af..b86843bf4f5d 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.h
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.h
@@ -173,6 +173,8 @@ void intel_runtime_pm_init_early(struct intel_runtime_pm *rpm);
 void intel_runtime_pm_enable(struct intel_runtime_pm *rpm);
 void intel_runtime_pm_disable(struct intel_runtime_pm *rpm);
 void intel_runtime_pm_driver_release(struct intel_runtime_pm *rpm);
+void intel_runtime_pm_get_vsp(struct drm_i915_private *i915);
+void intel_runtime_pm_put_vsp(struct drm_i915_private *i915);
 
 intel_wakeref_t intel_runtime_pm_get(struct intel_runtime_pm *rpm);
 intel_wakeref_t intel_runtime_pm_get_if_in_use(struct intel_runtime_pm *rpm);
-- 
2.26.2