linux-kernel - Re: [PATCH 2/2] media: verisilicon: Avoid G2 bus error while decoding H.264 and HEVC

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Message-ID: <53cb1a8e87f80d8bb1a9b6463077a99b2268e46c.camel@pengutronix.de>
Date: Mon, 24 Nov 2025 18:42:57 +0100
From: Lucas Stach <l.stach@...gutronix.de>
To: ming.qian@....nxp.com, linux-media@...r.kernel.org
Cc: 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, 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 2/2] media: verisilicon: Avoid G2 bus error while
 decoding H.264 and HEVC

Hi Ming,

Am Freitag, dem 21.11.2025 um 16:19 +0800 schrieb
ming.qian@....nxp.com:
> 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 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.
> 
Is there any more info available on what's actually causing the hang?
Is there some kind of overflow of the interconnect request capacity?

I'm asking to understand the issue a bit better, as locking both
decoder instances against each other seems like a pretty big hammer.

Regards,
Lucas

> Fixes: cb5dd5a0fa518 ("media: hantro: Introduce G2/HEVC decoder")
> Signed-off-by: Ming Qian <ming.qian@....nxp.com>
> ---
>  drivers/media/platform/verisilicon/hantro.h   |  1 +
>  .../media/platform/verisilicon/hantro_drv.c   | 26 +++++++++++++++++++
>  .../media/platform/verisilicon/imx8m_vpu_hw.c |  4 +++
>  3 files changed, 31 insertions(+)
> 
> diff --git a/drivers/media/platform/verisilicon/hantro.h b/drivers/media/platform/verisilicon/hantro.h
> index e0fdc4535b2d..8baebf767d26 100644
> --- a/drivers/media/platform/verisilicon/hantro.h
> +++ b/drivers/media/platform/verisilicon/hantro.h
> @@ -101,6 +101,7 @@ struct hantro_variant {
>  	unsigned int double_buffer : 1;
>  	unsigned int legacy_regs : 1;
>  	unsigned int late_postproc : 1;
> +	atomic_t *shared_resource;
>  };
>  
>  /**
> diff --git a/drivers/media/platform/verisilicon/hantro_drv.c b/drivers/media/platform/verisilicon/hantro_drv.c
> index 60b95b5d8565..036ce43c9359 100644
> --- a/drivers/media/platform/verisilicon/hantro_drv.c
> +++ b/drivers/media/platform/verisilicon/hantro_drv.c
> @@ -19,6 +19,7 @@
>  #include <linux/slab.h>
>  #include <linux/videodev2.h>
>  #include <linux/workqueue.h>
> +#include <linux/iopoll.h>
>  #include <media/v4l2-event.h>
>  #include <media/v4l2-mem2mem.h>
>  #include <media/videobuf2-core.h>
> @@ -93,6 +94,9 @@ static void hantro_job_finish(struct hantro_dev *vpu,
>  
>  	clk_bulk_disable(vpu->variant->num_clocks, vpu->clocks);
>  
> +	if (vpu->variant->shared_resource)
> +		atomic_cmpxchg(vpu->variant->shared_resource, 0, 1);
> +
>  	hantro_job_finish_no_pm(vpu, ctx, result);
>  }
>  
> @@ -166,12 +170,34 @@ void hantro_end_prepare_run(struct hantro_ctx *ctx)
>  			      msecs_to_jiffies(2000));
>  }
>  
> +static int hantro_wait_shared_resource(struct hantro_dev *vpu)
> +{
> +	u32 data;
> +	int ret;
> +
> +	if (!vpu->variant->shared_resource)
> +		return 0;
> +
> +	ret = read_poll_timeout(atomic_cmpxchg, data, data, 10, 300 * NSEC_PER_MSEC, false,
> +				vpu->variant->shared_resource, 1, 0);
> +	if (ret) {
> +		dev_err(vpu->dev, "Failed to wait shared resource\n");
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
>  static void device_run(void *priv)
>  {
>  	struct hantro_ctx *ctx = priv;
>  	struct vb2_v4l2_buffer *src, *dst;
>  	int ret;
>  
> +	ret = hantro_wait_shared_resource(ctx->dev);
> +	if (ret < 0)
> +		goto err_cancel_job;
> +
>  	src = hantro_get_src_buf(ctx);
>  	dst = hantro_get_dst_buf(ctx);
>  
> diff --git a/drivers/media/platform/verisilicon/imx8m_vpu_hw.c b/drivers/media/platform/verisilicon/imx8m_vpu_hw.c
> index 5be0e2e76882..1b3a0bfbf890 100644
> --- a/drivers/media/platform/verisilicon/imx8m_vpu_hw.c
> +++ b/drivers/media/platform/verisilicon/imx8m_vpu_hw.c
> @@ -324,6 +324,8 @@ static const char * const imx8mq_reg_names[] = { "g1", "g2", "ctrl" };
>  static const char * const imx8mq_g1_clk_names[] = { "g1" };
>  static const char * const imx8mq_g2_clk_names[] = { "g2" };
>  
> +static atomic_t imx8mq_shared_resource = ATOMIC_INIT(1);
> +
>  const struct hantro_variant imx8mq_vpu_variant = {
>  	.dec_fmts = imx8m_vpu_dec_fmts,
>  	.num_dec_fmts = ARRAY_SIZE(imx8m_vpu_dec_fmts),
> @@ -356,6 +358,7 @@ 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 = &imx8mq_shared_resource,
>  };
>  
>  const struct hantro_variant imx8mq_vpu_g2_variant = {
> @@ -371,6 +374,7 @@ 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 = &imx8mq_shared_resource,
>  };
>  
>  const struct hantro_variant imx8mm_vpu_g1_variant = {