[PATCH v3 2/2] drm/vc4: Allocated/liberate the binner BO at firstopen/lastclose

[Paul Kocialkowski]

The binner BO is a pre-requisite to GPU operations, so we must ensure
that it is always allocated when the GPU is in use. Currently, we are
allocating it at probe time and liberating/allocating it during runtime
pm cycles.

First, since the binner buffer is only required for GPU rendering, it's
a waste to allocate it when the driver probes since internal users of
the driver (such as fbcon) won't try to use the GPU.

Move the allocation/liberation to the firstopen/lastclose instead to
only allocate it when userspace has opened the device and adapt the IRQ
handler to return early when no binner BO was allocated yet.

Second, because the buffer is allocated from the same pool as other GPU
buffers, we might run into a situation where we are out of memory at
runtime resume. This causes the binner BO allocation to fail and results
in all subsequent operations to fail, resulting in a major hang in
userspace.

As a result, keep the buffer alive during runtime pm.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@xxxxxxxxxxx>
Reviewed-by: Eric Anholt <eric@xxxxxxxxxx>
---
 drivers/gpu/drm/vc4/vc4_drv.c | 26 ++++++++++++++++++++++++++
 drivers/gpu/drm/vc4/vc4_drv.h |  1 +
 drivers/gpu/drm/vc4/vc4_irq.c |  3 +++
 drivers/gpu/drm/vc4/vc4_v3d.c | 15 +--------------
 4 files changed, 31 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_drv.c b/drivers/gpu/drm/vc4/vc4_drv.c
index 3227706700f9..605dc50613e3 100644
--- a/drivers/gpu/drm/vc4/vc4_drv.c
+++ b/drivers/gpu/drm/vc4/vc4_drv.c
@@ -134,6 +134,30 @@ static void vc4_close(struct drm_device *dev, struct drm_file *file)
 	kfree(vc4file);
 }
 
+static int vc4_firstopen(struct drm_device *drm)
+{
+	struct vc4_dev *vc4 = to_vc4_dev(drm);
+	int ret;
+
+	if (!vc4->bin_bo) {
+		ret = vc4_allocate_bin_bo(drm);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static void vc4_lastclose(struct drm_device *drm)
+{
+	struct vc4_dev *vc4 = to_vc4_dev(drm);
+
+	if (vc4->bin_bo) {
+		drm_gem_object_put_unlocked(&vc4->bin_bo->base.base);
+		vc4->bin_bo = NULL;
+	}
+}
+
 static const struct vm_operations_struct vc4_vm_ops = {
 	.fault = vc4_fault,
 	.open = drm_gem_vm_open,
@@ -180,6 +204,8 @@ static struct drm_driver vc4_drm_driver = {
 			    DRIVER_SYNCOBJ),
 	.open = vc4_open,
 	.postclose = vc4_close,
+	.firstopen = vc4_firstopen,
+	.lastclose = vc4_lastclose,
 	.irq_handler = vc4_irq,
 	.irq_preinstall = vc4_irq_preinstall,
 	.irq_postinstall = vc4_irq_postinstall,
diff --git a/drivers/gpu/drm/vc4/vc4_drv.h b/drivers/gpu/drm/vc4/vc4_drv.h
index 7a3c093e7443..f52bb21e9885 100644
--- a/drivers/gpu/drm/vc4/vc4_drv.h
+++ b/drivers/gpu/drm/vc4/vc4_drv.h
@@ -808,6 +808,7 @@ extern struct platform_driver vc4_v3d_driver;
 int vc4_v3d_debugfs_ident(struct seq_file *m, void *unused);
 int vc4_v3d_debugfs_regs(struct seq_file *m, void *unused);
 int vc4_v3d_get_bin_slot(struct vc4_dev *vc4);
+int vc4_allocate_bin_bo(struct drm_device *drm);
 
 /* vc4_validate.c */
 int
diff --git a/drivers/gpu/drm/vc4/vc4_irq.c b/drivers/gpu/drm/vc4/vc4_irq.c
index 4cd2ccfe15f4..efaba2b02f6c 100644
--- a/drivers/gpu/drm/vc4/vc4_irq.c
+++ b/drivers/gpu/drm/vc4/vc4_irq.c
@@ -64,6 +64,9 @@ vc4_overflow_mem_work(struct work_struct *work)
 	struct vc4_exec_info *exec;
 	unsigned long irqflags;
 
+	if (!bo)
+		return;
+
 	bin_bo_slot = vc4_v3d_get_bin_slot(vc4);
 	if (bin_bo_slot < 0) {
 		DRM_ERROR("Couldn't allocate binner overflow mem\n");
diff --git a/drivers/gpu/drm/vc4/vc4_v3d.c b/drivers/gpu/drm/vc4/vc4_v3d.c
index e47e29426078..e04a51a75f01 100644
--- a/drivers/gpu/drm/vc4/vc4_v3d.c
+++ b/drivers/gpu/drm/vc4/vc4_v3d.c
@@ -218,7 +218,7 @@ int vc4_v3d_get_bin_slot(struct vc4_dev *vc4)
  * overall CMA pool before they make scenes complicated enough to run
  * out of bin space.
  */
-static int vc4_allocate_bin_bo(struct drm_device *drm)
+int vc4_allocate_bin_bo(struct drm_device *drm)
 {
 	struct vc4_dev *vc4 = to_vc4_dev(drm);
 	struct vc4_v3d *v3d = vc4->v3d;
@@ -303,9 +303,6 @@ static int vc4_v3d_runtime_suspend(struct device *dev)
 
 	vc4_irq_uninstall(vc4->dev);
 
-	drm_gem_object_put_unlocked(&vc4->bin_bo->base.base);
-	vc4->bin_bo = NULL;
-
 	clk_disable_unprepare(v3d->clk);
 
 	return 0;
@@ -317,10 +314,6 @@ static int vc4_v3d_runtime_resume(struct device *dev)
 	struct vc4_dev *vc4 = v3d->vc4;
 	int ret;
 
-	ret = vc4_allocate_bin_bo(vc4->dev);
-	if (ret)
-		return ret;
-
 	ret = clk_prepare_enable(v3d->clk);
 	if (ret != 0)
 		return ret;
@@ -384,12 +377,6 @@ static int vc4_v3d_bind(struct device *dev, struct device *master, void *data)
 	if (ret != 0)
 		return ret;
 
-	ret = vc4_allocate_bin_bo(drm);
-	if (ret) {
-		clk_disable_unprepare(v3d->clk);
-		return ret;
-	}
-
 	/* Reset the binner overflow address/size at setup, to be sure
 	 * we don't reuse an old one.
 	 */
-- 
2.21.0