Re: [PATCH 5/5] media: verisilicon: Flush IOMMU before decoding a frame

[Robin Murphy]

On 17/06/2025 5:01 pm, Benjamin Gaignard wrote:
> Le 17/06/2025 à 17:58, Jason Gunthorpe a écrit :
> > On Mon, Jun 16, 2025 at 04:55:53PM +0200, Benjamin Gaignard wrote:
> > > Flush the IOMMU mapping before decoding a frame to ensure that all 
> > > memory
> > > translations are properly applied.
> > >
> > > Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>
> > > ---
> > >   drivers/media/platform/verisilicon/hantro_drv.c | 11 +++++++++++
> > >   1 file changed, 11 insertions(+)
> > This is a really big red flag.
> >
> > iommu translations are supposed to be controlled by the iommu driver
> > and should be flushed as part of the iommu map/unmap flows. It should
> > never be necessary to do something like this.
>
> I have redone tests without this patch and the decode is perform correctly.
> I will drop it in the next version.
> I think I have fix the reference frame management in the driver so it 
> becomes
> useless.

If it turns out the hardware does require a TLBI to guarantee new 
mappings are visible, though, then the correct way is to implement the 
iotlb_sync_map op.

Thanks,
Robin.