Re: [PATCH v8 0/6] arm/arm64: mediatek: Fix mmsys device probing
From: Enric Balletbo i Serra
Date: Fri Feb 21 2020 - 03:57:06 EST
Hi CK,
Thanks for your quick answer.
On 21/2/20 5:39, CK Hu wrote:
> Hi, Enric:
>
> On Thu, 2020-02-20 at 18:21 +0100, Enric Balletbo i Serra wrote:
>> 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'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.
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.
> Regards,
> CK
>
>>
>> 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
>>
>