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

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Message-ID: <d282811a-866d-4ca8-b9f6-fc1da3a7565e@oss.nxp.com>
Date: Mon, 24 Nov 2025 09:38:15 +0800
From: "Ming Qian(OSS)" <ming.qian@....nxp.com>
To: Frank Li <Frank.li@....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

Hi Frank,

On 11/22/2025 12:08 AM, Frank Li wrote:
> 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

G1 and G2 are two different devices. If I were to use a mutex, I would
need to define a global mutex. Therefore, to avoid using a global mutex,
I only define a static atomic variable.

If a static mutex is acceptable, I think I can change it to a mutex.

Regards,
Ming

>> +
>> +	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
>>