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

[Dmitry Baryshkov]

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.

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

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

> 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

--
With best wishes
Dmitry