Re: [PATCH v3 3/3] media: verisilicon: Avoid G2 bus error while decoding H.264 and HEVC

[Frank Li <Frank.li@nxp.com>]

On Thu, Dec 04, 2025 at 01:15:35PM -0500, Nicolas Dufresne wrote:
> Hi Frank,
>
> Le jeudi 04 décembre 2025 à 12:34 -0500, Frank Li a écrit :
> > > +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?
>
> shared_devices is an array of of_device_id we match against. All the matching
> devices will share the same v4l2_m2m_dev (aka m2m scheduler). Typically, both
> cores will be schedule as one. This achieve what alternate operations without
> active polling or blocking locks/mutex.

Okay, but this code require shared_devices==NULL's device probe firstly.
generally not order guaranteed, if there are not depentance at DT.

Does VPU always probe before g1/g2?

and if there are two VPU instances, what's happen?

Frank

>
> For this platform, we only matched against the compatible for simplicity, since
> we know there is only one of each type. I've suggested this method to Ming,
> since it will make it really easy to apply such a quirk if other hardware have
> problems or design constraints.
>
> regards,
> Nicolas