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

[Abhinav Kumar]

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.
>
> 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.

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.
>
> Thanks!
>
> - Marijn
>
> >   		return ret;
> > +	}
> >   
> >   	return ret;
> >   }
> > --
> > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> > a Linux Foundation Collaborative Project