Re: [PATCH 2/4] gpu: host1x: Enable gather filter

[Mikko Perttunen]

On 08/21/2017 08:27 PM, Mikko Perttunen wrote:
> On 08/20/2017 07:59 PM, Dmitry Osipenko wrote:
> > On 20.08.2017 19:44, Dmitry Osipenko wrote:
> > > On 20.08.2017 19:24, Dmitry Osipenko wrote:
> > > > On 18.08.2017 19:15, Mikko Perttunen wrote:
> > > > > The gather filter is a feature present on Tegra124 and newer where the
> > > > > hardware prevents GATHERed command buffers from executing commands
> > > > > normally reserved for the CDMA pushbuffer which is maintained by the
> > > > > kernel driver.
> > > > >
> > > > > This commit enables the gather filter on all supporting hardware.
> > > > >
> > > > > Signed-off-by: Mikko Perttunen <mperttunen@xxxxxxxxxx>
> > > > > ---
> > > > >   drivers/gpu/host1x/hw/channel_hw.c          | 22 
> > > > > ++++++++++++++++++++++
> > > > >   drivers/gpu/host1x/hw/hw_host1x04_channel.h | 12 ++++++++++++
> > > > >   drivers/gpu/host1x/hw/hw_host1x05_channel.h | 12 ++++++++++++
> > > > >   3 files changed, 46 insertions(+)
> > > > >
> > > > > diff --git a/drivers/gpu/host1x/hw/channel_hw.c 
> > > > > b/drivers/gpu/host1x/hw/channel_hw.c
> > > > > index 0161da331702..5c0dc6bb51d1 100644
> > > > > --- a/drivers/gpu/host1x/hw/channel_hw.c
> > > > > +++ b/drivers/gpu/host1x/hw/channel_hw.c
> > > > > @@ -181,10 +181,32 @@ static int channel_submit(struct host1x_job 
> > > > > *job)
> > > > >       return err;
> > > > >   }
> > > > > +static void enable_gather_filter(struct host1x *host,
> > > > > +                 struct host1x_channel *ch)
> > > > > +{
> > > > > +#if HOST1X_HW >= 6
> > > > > +    u32 val;
> > > > > +
> > > > > +    if (!host->hv_regs)
> > > > > +        return;
> > > >
> > > > Is it really possible that gather filter could be not present on HW 
> > > > without
> > > > hypervisor? Maybe there is other way to enable it in that case?
>
> The hardware may have the hypervisor but Linux may be running as a 
> virtual machine without access to the hypervisor, in which case we 
> cannot access the registers, and it's the responsibility of the other OS 
> acting as hypervisor to enable the gather filter.
>
> > > > Is possible at all that hypervisor could be missed?
> > >
> > > BTW, this is also incoherent with the 'syncpoint protection' patch 
> > > which doesn't
> > > check for hypervisor presence.
> >
> > However, I noticed that check and it's wrongly placed ;) See comment 
> > to the
> > 'syncpoint protection' patch.

Also - thanks, I added the missing check to that patch :)

> >
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