On 12/12/2024 12:52 AM, Dmitry Baryshkov wrote:
On Thu, 12 Dec 2024 at 04:59, Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx> wrote:
On 12/11/2024 3:41 PM, Dmitry Baryshkov wrote:
Having I/O regions inside a msm_dp_catalog_private() results in extra
layers of one-line wrappers for accessing the data. Move I/O region base
and size to the globally visible struct msm_dp_catalog.
Reviewed-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
---
drivers/gpu/drm/msm/dp/dp_catalog.c | 457 +++++++++++++++---------------------
drivers/gpu/drm/msm/dp/dp_catalog.h | 12 +
2 files changed, 197 insertions(+), 272 deletions(-)
Fundamentally, the whole point of catalog was that it needs to be the
only place where we want to access the registers. Thats how this really
started.
This pre-dates my time with the DP driver but as I understand thats what
it was for.
Basically separating out the logical abstraction vs actual register writes .
If there are hardware sequence differences within the controller reset
OR any other register offsets which moved around, catalog should have
been able to absorb it without that spilling over to all the layers.
So for example, if we call dp_ctrl_reset() --> ctrl->catalog->reset_ctrl()
Then the reset_ctrl op of the catalog should manage any controller
version differences within the reset sequence.
The problem is that the register-level writes are usually not the best
abstraction. So, instead of designing the code around dp_catalog I'd
prefer to see actual hw / programming changes first.
So thats the issue here. If we did end up with registers and sequences
different for controller versions, the ctrl layer was expected to just
call a reset() op for example similar to the DPU example you gave. And
as you rightly noted, the dpu_hw_xxx files only expose the ops based on
version and the upper layers were supposed to just call into the ops
without knowing the register level details. Thats pretty much what
dp_ctrl tried to do here. We did not want to expose all the register
defines in those layers. This series is doing exactly opposite of that.
We do not use or have catalog ops today so it looks redundant as we just
call the dp_catalog APIs directly but that was really the intention.
Another reason which was behind this split but not applicable to current
upstream driver is that the AUX is part of the PHY driver in upstream
but in downstream, that remains a part of catalog and as we know the AUX
component keeps changing with chipsets especially the settings. That was
the reason of keeping catalog separate and the only place which should
deal with registers and not the entire DP driver.
The second point seems not applicable to this driver but first point
still is. I do admit there is re-direction like ctrl->catalog
instead of just writing it within dp_ctrl itself but the redirection was
only because ctrl layers were not really meant to deal with the register
programming. So for example, now with patch 7 of this series every
register being written to i exposed in dp_ctrl.c and likewise for other
files. That seems unnecessary. Because if we do end up with some
variants which need separate registers written, then we will now have to
end up touching every file as opposed to only touching dp_catalog.
Yes. I think that it's a bonus, not a problem. We end up touching the
files that are actually changed, so we see what is happening. Quite
frequently register changes are paired with the functionality changes.
Not exactly. Why should dp_ctrl really know that some register offset or
some block shift happened for example. It only needs to know when to
reset the hardware and not how. Thats the separation getting broken with
this.
For example (a very simple and dumb one), when designing code around
dp_catalog you ended up adding separate _p1 handlers.
Doing that from the data source point of view demands adding a stream_id param.
I have not checked your comment on that series here but if your concern
is stream_id should not be stored in the catalog but just passed, thats
fine, we can change it. stream_id as a param is needed anyway because
the register programming layer needs to know which offset to use. This
series is not mitigating that fact.
In the DPU driver we also have version-related conditionals in the HW
modules rather than pushing all data access to dpu_hw_catalog.c &
counterparts.
The dpu_hw_catalog.c and the dp_catalog.c are not the right files to
compare with each other. dp_catalog.c should be compared with
dpu_hw_xxx.c and as you noted, DPU version dependencies are handled in
those files only and not all over the files like what this series is doing.
I think it's better to make DP driver reflect DPU rather than keeping
a separate wrapper for no particular reason (note, DPU has hardware
abstractions, but on a block level, not on a register level).
Thats the issue here. DPU hardware blocks are arranged according to the
sub-blocks both in the software interface document and hence the code
matches it file-by-file. DP registers are grouped by clock domains and
the file separation we have today does not match that anyway. Hence
grouping link registers writes or pixel clock register writes into
dp_ctrl is also not correct that way. Let catalog handle that separation
internally which it already does.
