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

[Ming Qian(OSS)]

Hi Frank,

On 11/22/2025 12:08 AM, Frank Li wrote:
> On Fri, Nov 21, 2025 at 04:19:09PM +0800, ming.qian@xxxxxxxxxxx wrote:
> > From: Ming Qian <ming.qian@xxxxxxxxxxx>
> >
> > 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@xxxxxxxxxxx>
> > ---
> >   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