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

From: Marijn Suijten
Date: Tue Apr 25 2023 - 03:16:31 EST

On 2023-04-24 16:23:17, Abhinav Kumar wrote:
>
>
> 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.

To both: keep in mind that the range-checks we want to remove from
dpu_rm_init validate the ID (index?) of a block. This check is for the
*TYPE* of an INTF block, to skip it gracefully if no hardware is mapped
there. As per the first patch of this series SM6115/QCM2290 only have a
DSI interface which always sits at ID 1, and ID 0 has its TYPE set to
INTF_NONE and is skipped.

Hence we _should_ keep the graceful TYPE check in dpu_rm_init() to skip
calling this function _and assigning it to the rm->hw_intf array_. But
I can remove the second TYPE check here in dpu_hw_intf_init() if you
prefer.

- Marijn