Hi, Matthias:

On Fri, 2020-02-21 at 11:24 +0100, Matthias Brugger wrote:

On 21/02/2020 10:27, CK Hu wrote:

quoted

Hi, Enric:

On Fri, 2020-02-21 at 09:56 +0100, Enric Balletbo i Serra wrote:

quoted

Hi CK,

Thanks for your quick answer.

On 21/2/20 5:39, CK Hu wrote:

quoted

Hi, Enric:

On Thu, 2020-02-20 at 18:21 +0100, Enric Balletbo i Serra wrote:

quoted

Dear all,

Those patches are intended to solve an old standing issue on some
Mediatek devices (mt8173, mt2701 and mt2712) in a slightly different way
to the precedent series.

Up to now both drivers, clock and drm are probed with the same device tree
compatible. But only the first driver get probed, which in effect breaks
graphics on those devices.

The version eight of the series tries to solve the problem with a
different approach than the previous series but similar to how is solved
on other Mediatek devices.

The MMSYS (Multimedia subsystem) in Mediatek SoCs has some registers to
control clock gates (which is used in the clk driver) and some registers
to set the routing and enable the differnet blocks of the display
and MDP (Media Data Path) subsystem. On this series the clk driver is
not a pure clock controller but a system controller that can provide
access to the shared registers between the different drivers that need
it (mediatek-drm and mediatek-mdp). And the biggest change is, that in
this version, clk driver is the entry point (parent) which will trigger
the probe of the corresponding mediatek-drm driver and pass its MMSYS
platform data for display configuration.

When mmsys is a system controller, I prefer to place mmsys in
drivers/soc/mediatek, and it share registers for clock, display, and mdp
driver. This means the probe function is placed in
drivers/soc/mediatek ,its display clock function, mdp clock function are
placed in drivers/clk, display routing are placed in drivers/gpu/drm,
and mdp routing are placed in dirvers/video.

I understand what you mean but I am not sure this makes the code clearer and
useful. The driver in drivers/soc/mediatek will be a simple dummy implementation
of a "simple-mfd" device (a driver that simply matches with
"mediatek,mt8173-mmsys" and instantiates the "clk-mt8173-mm" and the
"mediatek-drm" driver (note that mediatek-mdp" is already instantiated via
device-tree).

It's clear that mmsys is neither a pure clock controller nor a pure
routing controller for display and mdp. 

quoted

It'd be nice had a proper device-tree with a "simple-mfd" for mmsys from the
beginning representing how really hardwware is, but I think that, change this
now, will break backward compatibility.

Maybe this is a solution. Current device tree would work only on old
kernel version with a bug, so this mean there is no any device tree
works on kernel version without bug. Why do we compatible with such
device tree?

The idea behind this is, that the device-tree could be passed by some boot
firmware, so that the OS do not care about it. For this we need a stable DTS as
otherwise newer kernel with older FW would break.

DTS is supposed to be just a different description of the HW like ACPI. So it
has to be compatible (newer kernel with older DTS and if possible vice versa).

In my view, there is no FW (except some bug-inside FW) which works on
this dts, so this dts is in a initial state. I think the compatibility
is based on that dts correctly describe the HW. If we find this dts does
not correctly describe the HW and it's in a initial state, should we
still make it compatible?

If you have better solution, just let's forget this.

Regards,
CK

Regards,
Matthias

quoted

Regards,
CK

quoted

IMHO I think that considering the clk driver as entry point is fine, but this is
something that the clock maintainers should decide.

Also note that this is not only a MT8173 problem I am seeing the same problem on
all other Mediatek SoCs.

Thanks.

quoted

Regards,
CK

quoted

All this series was tested on the Acer R13 Chromebook only.

For reference, here are the links to the old discussions:

* v7: https://patchwork.kernel.org/project/linux-mediatek/list/?series=241217
* v6: https://patchwork.kernel.org/project/linux-mediatek/list/?series=213219
* v5: https://patchwork.kernel.org/project/linux-mediatek/list/?series=44063
* v4:
  * https://patchwork.kernel.org/patch/10530871/
  * https://patchwork.kernel.org/patch/10530883/
  * https://patchwork.kernel.org/patch/10530885/
  * https://patchwork.kernel.org/patch/10530911/
  * https://patchwork.kernel.org/patch/10530913/
* v3:
  * https://patchwork.kernel.org/patch/10367857/
  * https://patchwork.kernel.org/patch/10367861/
  * https://patchwork.kernel.org/patch/10367877/
  * https://patchwork.kernel.org/patch/10367875/
  * https://patchwork.kernel.org/patch/10367885/
  * https://patchwork.kernel.org/patch/10367883/
  * https://patchwork.kernel.org/patch/10367889/
  * https://patchwork.kernel.org/patch/10367907/
  * https://patchwork.kernel.org/patch/10367909/
  * https://patchwork.kernel.org/patch/10367905/
* v2: No relevant discussion, see v3
* v1:
  * https://patchwork.kernel.org/patch/10016497/
  * https://patchwork.kernel.org/patch/10016499/
  * https://patchwork.kernel.org/patch/10016505/
  * https://patchwork.kernel.org/patch/10016507/

Best regards,
 Enric

Changes in v8:
- Be a builtin_platform_driver like other mediatek mmsys drivers.
- New patches introduced in this series.

Changes in v7:
- Add R-by from CK
- Add R-by from CK
- Fix check of return value of of_clk_get
- Fix identation
- Free clk_data->clks as well
- Get rid of private data structure

Enric Balletbo i Serra (2):
  drm/mediatek: Move MMSYS configuration to include/linux/platform_data
  clk/drm: mediatek: Fix mediatek-drm device probing

Matthias Brugger (4):
  drm/mediatek: Use regmap for register access
  drm/mediatek: Omit warning on probe defers
  media: mtk-mdp: Check return value of of_clk_get
  clk: mediatek: mt8173: Switch MMSYS to platform driver

 drivers/clk/mediatek/Kconfig                  |   6 +
 drivers/clk/mediatek/Makefile                 |   1 +
 drivers/clk/mediatek/clk-mt2701-mm.c          |  30 +++
 drivers/clk/mediatek/clk-mt2712-mm.c          |  44 +++++
 drivers/clk/mediatek/clk-mt8173-mm.c          | 172 ++++++++++++++++++
 drivers/clk/mediatek/clk-mt8173.c             | 104 -----------
 drivers/gpu/drm/mediatek/mtk_disp_color.c     |   5 +-
 drivers/gpu/drm/mediatek/mtk_disp_ovl.c       |   5 +-
 drivers/gpu/drm/mediatek/mtk_disp_rdma.c      |   5 +-
 drivers/gpu/drm/mediatek/mtk_dpi.c            |  12 +-
 drivers/gpu/drm/mediatek/mtk_drm_crtc.c       |   4 +-
 drivers/gpu/drm/mediatek/mtk_drm_ddp.c        |  53 +++---
 drivers/gpu/drm/mediatek/mtk_drm_ddp.h        |   4 +-
 drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h   |  56 +-----
 drivers/gpu/drm/mediatek/mtk_drm_drv.c        | 113 +-----------
 drivers/gpu/drm/mediatek/mtk_drm_drv.h        |  13 +-
 drivers/gpu/drm/mediatek/mtk_dsi.c            |   8 +-
 drivers/gpu/drm/mediatek/mtk_hdmi.c           |   4 +-
 drivers/media/platform/mtk-mdp/mtk_mdp_comp.c |   6 +
 include/linux/platform_data/mtk_mmsys.h       |  73 ++++++++
 20 files changed, 401 insertions(+), 317 deletions(-)
 create mode 100644 drivers/clk/mediatek/clk-mt8173-mm.c
 create mode 100644 include/linux/platform_data/mtk_mmsys.h

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