[PATCH v2 2/2] media: verisilicon: Avoid G2 bus error while decoding H.264 and HEVC

[ming.qian@oss.nxp.com]

From: Ming Qian <ming.qian@oss.nxp.com>

For the i.MX8MQ platform, there is a hardware limitation: the g1 VPU and
g2 VPU cannot decode simultaneously; otherwise, it will cause below bus
error and produce corrupted pictures, even led to system hang.

[  110.527986] hantro-vpu 38310000.video-codec: frame decode timed out.
[  110.583517] hantro-vpu 38310000.video-codec: bus error detected.

Therefore, it is necessary to ensure that g1 and g2 operate alternately.
Then this allows for successful multi-instance decoding of H.264 and HEVC.

To achieve this, we can have g1 and g2 share the same v4l2_m2m_dev, and
then the v4l2_m2m_dev can handle the scheduling.

Fixes: cb5dd5a0fa518 ("media: hantro: Introduce G2/HEVC decoder")
Signed-off-by: Ming Qian <ming.qian@oss.nxp.com>
---
v2
- Abandon the waiting approach.
- Switch to a shared v4l2_m2m_dev solution.

 drivers/media/platform/verisilicon/hantro.h   |  2 +
 .../media/platform/verisilicon/hantro_drv.c   | 41 +++++++++++++++++--
 .../media/platform/verisilicon/imx8m_vpu_hw.c |  2 +
 3 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/drivers/media/platform/verisilicon/hantro.h b/drivers/media/platform/verisilicon/hantro.h
index e0fdc4535b2d..8a0583f95417 100644
--- a/drivers/media/platform/verisilicon/hantro.h
+++ b/drivers/media/platform/verisilicon/hantro.h
@@ -77,6 +77,7 @@ struct hantro_irq {
  * @double_buffer:		core needs double buffering
  * @legacy_regs:		core uses legacy register set
  * @late_postproc:		postproc must be set up at the end of the job
+ * @shared_resource:		flag of shared resource
  */
 struct hantro_variant {
 	unsigned int enc_offset;
@@ -101,6 +102,7 @@ struct hantro_variant {
 	unsigned int double_buffer : 1;
 	unsigned int legacy_regs : 1;
 	unsigned int late_postproc : 1;
+	unsigned int shared_resource : 1;
 };
 
 /**
diff --git a/drivers/media/platform/verisilicon/hantro_drv.c b/drivers/media/platform/verisilicon/hantro_drv.c
index 60b95b5d8565..f42b2df86806 100644
--- a/drivers/media/platform/verisilicon/hantro_drv.c
+++ b/drivers/media/platform/verisilicon/hantro_drv.c
@@ -35,6 +35,10 @@ module_param_named(debug, hantro_debug, int, 0644);
 MODULE_PARM_DESC(debug,
 		 "Debug level - higher value produces more verbose messages");
 
+static DEFINE_MUTEX(shared_dev_lock);
+static atomic_t shared_dev_ref_cnt = ATOMIC_INIT(0);
+static struct v4l2_m2m_dev *shared_m2m_dev;
+
 void *hantro_get_ctrl(struct hantro_ctx *ctx, u32 id)
 {
 	struct v4l2_ctrl *ctrl;
@@ -1035,6 +1039,37 @@ static int hantro_disable_multicore(struct hantro_dev *vpu)
 	return 0;
 }
 
+static struct v4l2_m2m_dev *hantro_get_v4l2_m2m_dev(struct hantro_dev *vpu)
+{
+	if (!vpu->variant || !vpu->variant->shared_resource)
+		return v4l2_m2m_init(&vpu_m2m_ops);
+
+	scoped_guard(mutex, &shared_dev_lock) {
+		if (atomic_inc_return(&shared_dev_ref_cnt) == 1) {
+			shared_m2m_dev = v4l2_m2m_init(&vpu_m2m_ops);
+			if (IS_ERR(shared_m2m_dev))
+				atomic_dec(&shared_dev_ref_cnt);
+		}
+	}
+
+	return shared_m2m_dev;
+}
+
+static void hantro_put_v4l2_m2m_dev(struct hantro_dev *vpu)
+{
+	if (!vpu->variant || !vpu->variant->shared_resource)
+		v4l2_m2m_release(vpu->m2m_dev);
+
+	scoped_guard(mutex, &shared_dev_lock) {
+		if (!atomic_dec_return(&shared_dev_ref_cnt)) {
+			if (!IS_ERR(shared_m2m_dev)) {
+				v4l2_m2m_release(shared_m2m_dev);
+				shared_m2m_dev = NULL;
+			}
+		}
+	}
+}
+
 static int hantro_probe(struct platform_device *pdev)
 {
 	const struct of_device_id *match;
@@ -1186,7 +1221,7 @@ static int hantro_probe(struct platform_device *pdev)
 	}
 	platform_set_drvdata(pdev, vpu);
 
-	vpu->m2m_dev = v4l2_m2m_init(&vpu_m2m_ops);
+	vpu->m2m_dev = hantro_get_v4l2_m2m_dev(vpu);
 	if (IS_ERR(vpu->m2m_dev)) {
 		v4l2_err(&vpu->v4l2_dev, "Failed to init mem2mem device\n");
 		ret = PTR_ERR(vpu->m2m_dev);
@@ -1225,7 +1260,7 @@ static int hantro_probe(struct platform_device *pdev)
 	hantro_remove_enc_func(vpu);
 err_m2m_rel:
 	media_device_cleanup(&vpu->mdev);
-	v4l2_m2m_release(vpu->m2m_dev);
+	hantro_put_v4l2_m2m_dev(vpu);
 err_v4l2_unreg:
 	v4l2_device_unregister(&vpu->v4l2_dev);
 err_clk_unprepare:
@@ -1248,7 +1283,7 @@ static void hantro_remove(struct platform_device *pdev)
 	hantro_remove_dec_func(vpu);
 	hantro_remove_enc_func(vpu);
 	media_device_cleanup(&vpu->mdev);
-	v4l2_m2m_release(vpu->m2m_dev);
+	hantro_put_v4l2_m2m_dev(vpu);
 	v4l2_device_unregister(&vpu->v4l2_dev);
 	clk_bulk_unprepare(vpu->variant->num_clocks, vpu->clocks);
 	reset_control_assert(vpu->resets);
diff --git a/drivers/media/platform/verisilicon/imx8m_vpu_hw.c b/drivers/media/platform/verisilicon/imx8m_vpu_hw.c
index 5be0e2e76882..5111ce5c36f3 100644
--- a/drivers/media/platform/verisilicon/imx8m_vpu_hw.c
+++ b/drivers/media/platform/verisilicon/imx8m_vpu_hw.c
@@ -356,6 +356,7 @@ const struct hantro_variant imx8mq_vpu_g1_variant = {
 	.num_irqs = ARRAY_SIZE(imx8mq_irqs),
 	.clk_names = imx8mq_g1_clk_names,
 	.num_clocks = ARRAY_SIZE(imx8mq_g1_clk_names),
+	.shared_resource = 1,
 };
 
 const struct hantro_variant imx8mq_vpu_g2_variant = {
@@ -371,6 +372,7 @@ const struct hantro_variant imx8mq_vpu_g2_variant = {
 	.num_irqs = ARRAY_SIZE(imx8mq_g2_irqs),
 	.clk_names = imx8mq_g2_clk_names,
 	.num_clocks = ARRAY_SIZE(imx8mq_g2_clk_names),
+	.shared_resource = 1,
 };
 
 const struct hantro_variant imx8mm_vpu_g1_variant = {
-- 
2.52.0