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Message-ID: <aTHGJzVKa7PbEifJ@lizhi-Precision-Tower-5810>
Date: Thu, 4 Dec 2025 12:34:31 -0500
From: Frank Li <Frank.li@....com>
To: ming.qian@....nxp.com
Cc: linux-media@...r.kernel.org, mchehab@...nel.org,
hverkuil-cisco@...all.nl, nicolas@...fresne.ca,
benjamin.gaignard@...labora.com, p.zabel@...gutronix.de,
sebastian.fricke@...labora.com, shawnguo@...nel.org,
ulf.hansson@...aro.org, s.hauer@...gutronix.de,
kernel@...gutronix.de, festevam@...il.com, linux-imx@....com,
l.stach@...gutronix.de, peng.fan@....com, eagle.zhou@....com,
imx@...ts.linux.dev, linux-pm@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 3/3] media: verisilicon: Avoid G2 bus error while
decoding H.264 and HEVC
On Thu, Dec 04, 2025 at 05:08:11PM +0800, ming.qian@....nxp.com wrote:
> From: Ming Qian <ming.qian@....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 potentially lead 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.
> 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.
To achieve this, g1 and g2 share the same v4l2_m2m_dev, ...
>
> Fixes: cb5dd5a0fa518 ("media: hantro: Introduce G2/HEVC decoder")
> Co-developed-by: Nicolas Dufresne <nicolas.dufresne@...labora.com>
> Signed-off-by: Nicolas Dufresne <nicolas.dufresne@...labora.com>
> Signed-off-by: Ming Qian <ming.qian@....nxp.com>
> ---
> v3
> - Apply Nicolas's approach that use an array list to define the shared
> devices
>
> 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 | 42 +++++++++++++++++--
> .../media/platform/verisilicon/imx8m_vpu_hw.c | 8 ++++
> 3 files changed, 49 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/media/platform/verisilicon/hantro.h b/drivers/media/platform/verisilicon/hantro.h
> index e0fdc4535b2d..0353de154a1e 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_devices: an array of device ids that cannot run concurrently
> */
> 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;
> + const struct of_device_id *shared_devices;
> };
>
> /**
> diff --git a/drivers/media/platform/verisilicon/hantro_drv.c b/drivers/media/platform/verisilicon/hantro_drv.c
> index 60b95b5d8565..70160eaf3d15 100644
> --- a/drivers/media/platform/verisilicon/hantro_drv.c
> +++ b/drivers/media/platform/verisilicon/hantro_drv.c
> @@ -13,6 +13,7 @@
> #include <linux/clk.h>
> #include <linux/module.h>
> #include <linux/of.h>
> +#include <linux/of_platform.h>
> #include <linux/platform_device.h>
> #include <linux/pm.h>
> #include <linux/pm_runtime.h>
> @@ -1035,6 +1036,41 @@ 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)
> +{
> + struct device_node *node;
> + struct hantro_dev *shared_vpu;
> +
> + if (!vpu->variant || !vpu->variant->shared_devices)
> + goto init_new_m2m_dev;
I found only use shared_devices here, how to ensure that g1 and g2 operate
alternately by using shared_devices?
Frank
> +
> + for_each_matching_node(node, vpu->variant->shared_devices) {
> + struct platform_device *pdev;
> + struct v4l2_m2m_dev *m2m_dev;
> +
> + pdev = of_find_device_by_node(node);
> + of_node_put(node);
> +
> + if (!pdev)
> + continue;
> +
> + shared_vpu = platform_get_drvdata(pdev);
> + if (IS_ERR_OR_NULL(shared_vpu) || shared_vpu == vpu) {
> + platform_device_put(pdev);
> + continue;
> + }
> +
> + v4l2_m2m_get(shared_vpu->m2m_dev);
> + m2m_dev = shared_vpu->m2m_dev;
> + platform_device_put(pdev);
> +
> + return m2m_dev;
> + }
> +
> +init_new_m2m_dev:
> + return v4l2_m2m_init(&vpu_m2m_ops);
> +}
> +
> static int hantro_probe(struct platform_device *pdev)
> {
> const struct of_device_id *match;
> @@ -1186,7 +1222,7 @@ 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 +1261,7 @@ 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);
> + v4l2_m2m_put(vpu->m2m_dev);
> err_v4l2_unreg:
> v4l2_device_unregister(&vpu->v4l2_dev);
> err_clk_unprepare:
> @@ -1248,7 +1284,7 @@ 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);
> + v4l2_m2m_put(vpu->m2m_dev);
> 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..6f8e43b7f157 100644
> --- a/drivers/media/platform/verisilicon/imx8m_vpu_hw.c
> +++ b/drivers/media/platform/verisilicon/imx8m_vpu_hw.c
> @@ -343,6 +343,12 @@ const struct hantro_variant imx8mq_vpu_variant = {
> .num_regs = ARRAY_SIZE(imx8mq_reg_names)
> };
>
> +static const struct of_device_id imx8mq_vpu_shared_resources[] __initconst = {
> + { .compatible = "nxp,imx8mq-vpu-g1", },
> + { .compatible = "nxp,imx8mq-vpu-g2", },
> + { /* sentinel */ }
> +};
> +
> const struct hantro_variant imx8mq_vpu_g1_variant = {
> .dec_fmts = imx8m_vpu_dec_fmts,
> .num_dec_fmts = ARRAY_SIZE(imx8m_vpu_dec_fmts),
> @@ -356,6 +362,7 @@ 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_devices = imx8mq_vpu_shared_resources,
> };
>
> const struct hantro_variant imx8mq_vpu_g2_variant = {
> @@ -371,6 +378,7 @@ 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_devices = imx8mq_vpu_shared_resources,
> };
>
> const struct hantro_variant imx8mm_vpu_g1_variant = {
> --
> 2.52.0
>
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