Re: [Freedreno] [PATCH] drm/msm/dpu: add DSC range checking during resource reservation

[Abhinav Kumar]

On 4/11/2023 6:06 PM, Dmitry Baryshkov wrote:
> On 12/04/2023 01:32, Abhinav Kumar wrote:
> > Hi Marijn
> >
> > On 4/11/2023 3:24 PM, Marijn Suijten wrote:
> > > Again, don't forget to include previous reviewers in cc, please :)
> > >
> > > On 2023-04-11 14:09:40, Kuogee Hsieh wrote:
> > > > Perform DSC range checking to make sure correct DSC is requested before
> > > > reserve resource for it.
>
> nit: reserving
>
> > > This isn't performing any range checking for resource reservations /
> > > requests: this is only validating the constants written in our catalog
> > > and seems rather useless.  It isn't fixing any real bug either, so the
> > > Fixes: tag below seems extraneous.
> > >
> > > Given prior comments from Abhinav that "the kernel should be trusted",
> > > we should remove this validation for all the other blocks instead.
> >
> > The purpose of this check is that today all our blocks in RM use the 
> > DSC_* enum as the size.
> >
> > struct dpu_hw_blk *dsc_blks[DSC_MAX - DSC_0];
> >
> > If the device tree ends up with more DSC blocks than the DSC_* enum, 
> > how can we avoid this issue today? Not because its a bug in device 
> > tree but how many static number of DSCs are hard-coded in RM.
>
> We don't have these blocks in device tree. And dpu_hw_catalog shouldn't 
> use indices outside of enum dpu_dsc.

ah, my bad, i should have said catalog here. Okay so the expectation is 
that dpu_hw_catalog.c will program the indices to match the RM limits.

I still stand by the fact that the hardware capabilities coming from 
catalog should be trusted but this is just the SW index.

> Marijn proposed to pass struct dpu_foo_cfg directly to 
> dpu_hw_foo_init(). This will allow us to drop these checks completely.

Ah okay, sure, would like to see that then uniformly get rid of these 
checks.

> For the time being, I think it might be better to add these checks for 
> DSC for the sake of uniformity.

Yes, i think so too.

> > And like you said, this is not specific to DSC. Such checks are 
> > present for other blocks too.
> >
> > > > Fixes: c985d7bb64ff ("drm/msm/disp/dpu1: Add DSC support in RM")
> > > > Signed-off-by: Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx>
> > > > ---
> > > >   drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c | 10 +++++++++-
> > > >   1 file changed, 9 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c 
> > > > b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> > > > index f4dda88..95e58f1 100644
> > > > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> > > > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> > > > @@ -1,6 +1,7 @@
> > > >   // SPDX-License-Identifier: GPL-2.0-only
> > > >   /*
> > > >    * Copyright (c) 2016-2018, The Linux Foundation. All rights 
> > > > reserved.
> > > > + * Copyright (c) 2023 Qualcomm Innovation Center, Inc. All rights 
> > > > reserved.
> > > >    */
> > > >   #define pr_fmt(fmt)    "[drm:%s] " fmt, __func__
> > > > @@ -250,6 +251,11 @@ int dpu_rm_init(struct dpu_rm *rm,
> > > >           struct dpu_hw_dsc *hw;
> > > >           const struct dpu_dsc_cfg *dsc = &cat->dsc[i];
> > > > +        if (dsc->id < DSC_0 || dsc->id >= DSC_MAX) {
> > > > +            DPU_ERROR("skip dsc %d with invalid id\n", dsc->id);
> > > > +            continue;
> > > > +        }
> > > > +
> > > >           hw = dpu_hw_dsc_init(dsc->id, mmio, cat);
> > > >           if (IS_ERR_OR_NULL(hw)) {
> > > >               rc = PTR_ERR(hw);
> > > > @@ -557,8 +563,10 @@ static int _dpu_rm_make_reservation(
> > > >       }
> > > >       ret  = _dpu_rm_reserve_dsc(rm, global_state, enc, 
> > > > &reqs->topology);
> > > > -    if (ret)
> > > > +    if (ret) {
> > > > +        DPU_ERROR("unable to find appropriate DSC\n");
> > >
> > > This, while a nice addition, should go in a different patch.
>
> I'd agree here, a separate patch.
>
> > > Thanks!
> > >
> > > - Marijn
> > >
> > > >           return ret;
> > > > +    }
> > > >       return ret;
> > > >   }
> > > > --
> > > > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
> > > > Forum,
> > > > a Linux Foundation Collaborative Project