Re: [PATCH v2 3/3] drm/msm/dpu: Pass catalog pointers directly from RM instead of IDs

[Abhinav Kumar]

On 4/24/2023 3:54 PM, Dmitry Baryshkov wrote:
> On Tue, 25 Apr 2023 at 01:03, Marijn Suijten
> <marijn.suijten@xxxxxxxxxxxxxx> wrote:
> > On 2023-04-21 16:25:15, Abhinav Kumar wrote:
> > > On 4/21/2023 1:53 PM, Marijn Suijten wrote:
> > > > The Resource Manager already iterates over all available blocks from the
> > > > catalog, only to pass their ID to a dpu_hw_xxx_init() function which
> > > > uses an _xxx_offset() helper to search for and find the exact same
> > > > catalog pointer again to initialize the block with, fallible error
> > > > handling and all.
> > > >
> > > > Instead, pass const pointers to the catalog entries directly to these
> > > > _init functions and drop the for loops entirely, saving on both
> > > > readability complexity and unnecessary cycles at boot.
> > > >
> > > > Signed-off-by: Marijn Suijten <marijn.suijten@xxxxxxxxxxxxxx>
> > > > Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> > >
> > > Overall, a nice cleanup!
> > >
> > > One comment below.
> > >
> > > > ---
> > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.c        | 37 +++++----------------
> > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.h        | 14 ++++----
> > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.c        | 32 +++---------------
> > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.h        | 11 +++----
> > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dspp.c       | 38 ++++-----------------
> > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dspp.h       | 12 +++----
> > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_interrupts.h |  2 +-
> > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c       | 40 ++++++-----------------
> > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.h       | 12 +++----
> > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_lm.c         | 38 ++++-----------------
> > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_lm.h         | 10 +++---
> > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_merge3d.c    | 33 +++----------------
> > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_merge3d.h    | 14 ++++----
> > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_pingpong.c   | 33 +++----------------
> > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_pingpong.h   | 14 ++++----
> > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp.c       | 39 ++++------------------
> > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp.h       | 12 +++----
> > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_vbif.c       | 33 +++----------------
> > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_vbif.h       | 11 +++----
> > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_wb.c         | 33 ++++---------------
> > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_wb.h         | 11 +++----
> > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c           | 17 +++++-----
> > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c            | 18 +++++-----
> > > >    23 files changed, 139 insertions(+), 375 deletions(-)
> > >
> > > <snipped>
> > >
> > > > -struct dpu_hw_intf *dpu_hw_intf_init(enum dpu_intf idx,
> > > > -           void __iomem *addr,
> > > > -           const struct dpu_mdss_cfg *m)
> > > > +struct dpu_hw_intf *dpu_hw_intf_init(const struct dpu_intf_cfg *cfg,
> > > > +           void __iomem *addr)
> > > >    {
> > > >      struct dpu_hw_intf *c;
> > > > -   const struct dpu_intf_cfg *cfg;
> > > > +
> > > > +   if (cfg->type == INTF_NONE) {
> > > > +           pr_err("Cannot create interface hw object for INTF_NONE type\n");
> > > > +           return ERR_PTR(-EINVAL);
> > > > +   }
> > >
> > > The caller of dpu_hw_intf_init which is the RM already has protection
> > > for INTF_NONE, see below
> > >
> > >           for (i = 0; i < cat->intf_count; i++) {
> > >                   struct dpu_hw_intf *hw;
> > >                   const struct dpu_intf_cfg *intf = &cat->intf[i];
> > >
> > >                   if (intf->type == INTF_NONE) {
> > >                           DPU_DEBUG("skip intf %d with type none\n", i);
> > >                           continue;
> > >                   }
> > >                   if (intf->id < INTF_0 || intf->id >= INTF_MAX) {
> > >                           DPU_ERROR("skip intf %d with invalid id\n",
> > > intf->id);
> > >                           continue;
> > >                   }
> > >                   hw = dpu_hw_intf_init(intf->id, mmio, cat);
> > >
> > > So this part can be dropped.
> >
> > I mainly intended to keep original validation where _intf_offset would
> > skip INTF_NONE, and error out.  RM init is hence expected to filter out
> > INTF_NONE instead of running into that `-EINVAL`, which I maintained
> > here.
> >
> > If you think there won't be another caller of dpu_hw_intf_init, and that
> > such validation is hence excessive, I can remove it in a followup v3.
>
> I'd prefer to see the checks at dpu_rm to be dropped.
> dpu_hw_intf_init() (and other dpu_hw_foo_init() functions) should be
> self-contained. If they can not init HW block (e.g. because the index
> is out of the boundaries), they should return an error.

They already do that today because even without this it will call into 
_intf_offset() and that will bail out for INTF_NONE.

I feel this is a duplicated check because the caller with the loop needs 
to validate the index before passing it to dpu_hw_intf_init() otherwise 
the loop will get broken at the first return of the error and rest of 
the blocks will also not be initialized.


> > - Marijn
> >
> > > >      c = kzalloc(sizeof(*c), GFP_KERNEL);
> > > >      if (!c)
> > > >              return ERR_PTR(-ENOMEM);
> > > >
> > > > -   cfg = _intf_offset(idx, m, addr, &c->hw);
> > > > -   if (IS_ERR_OR_NULL(cfg)) {
> > > > -           kfree(c);
> > > > -           pr_err("failed to create dpu_hw_intf %d\n", idx);
> > > > -           return ERR_PTR(-EINVAL);
> > > > -   }
> > > > +   c->hw.blk_addr = addr + cfg->base;
> > > > +   c->hw.log_mask = DPU_DBG_MASK_INTF;
> > >
> > > <snipped>