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

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Message-ID: <aSCOZCJ2rSw7LAvE@lizhi-Precision-Tower-5810>
Date: Fri, 21 Nov 2025 11:08:04 -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 2/2] media: verisilicon: Avoid G2 bus error while
 decoding H.264 and HEVC

On Fri, Nov 21, 2025 at 04:19:09PM +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 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.
>
> 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(+)
>
...
>  #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;
> +	}

why not use a mutex?

mutex() lock here, unlock at hantro_job_finish(), if second instance
run to here, mutex() will block thread, until previous hantro_job_finish()
finish.

Frank
> +
> +	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);
...

>
> --
> 2.34.1
>