linux-kernel - Re: [PATCH v8 0/6] arm/arm64: mediatek: Fix mmsys device probing

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Date:   Fri, 21 Feb 2020 11:20:20 +0100
From:   Matthias Brugger <mbrugger@...e.com>
To:     CK Hu <ck.hu@...iatek.com>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Lee Jones <lee.jones@...aro.org>
Cc:     robh+dt@...nel.org, mark.rutland@....com, p.zabel@...gutronix.de,
        airlied@...ux.ie, mturquette@...libre.com, sboyd@...nel.org,
        ulrich.hecht+renesas@...il.com, laurent.pinchart@...asonboard.com,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        rdunlap@...radead.org, dri-devel@...ts.freedesktop.org,
        Weiyi Lu <weiyi.lu@...iatek.com>,
        Seiya Wang <seiya.wang@...iatek.com>,
        linux-clk@...r.kernel.org,
        Collabora Kernel ML <kernel@...labora.com>,
        mtk01761 <wendell.lin@...iatek.com>,
        Allison Randal <allison@...utok.net>,
        Thomas Gleixner <tglx@...utronix.de>, wens@...e.org,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Houlong Wei <houlong.wei@...iatek.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        sean.wang@...iatek.com, frank-w@...lic-files.de,
        Minghsiu Tsai <minghsiu.tsai@...iatek.com>,
        Andrew-CT Chen <andrew-ct.chen@...iatek.com>,
        linux-mediatek@...ts.infradead.org, hsinyi@...omium.org,
        linux-arm-kernel@...ts.infradead.org,
        Richard Fontana <rfontana@...hat.com>,
        linux-kernel@...r.kernel.org, matthias.bgg@...nel.org,
        Daniel Vetter <daniel@...ll.ch>,
        Fabien Parent <fparent@...libre.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Nicolas Boichat <drinkcat@...omium.org>,
        Owen Chen <owen.chen@...iatek.com>
Subject: Re: [PATCH v8 0/6] arm/arm64: mediatek: Fix mmsys device probing

Adding Lee Jones.

On 21/02/2020 05:39, 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.
> 

Which sounds to me like a mfd device. Something we already tried and got a
NACKed by Lee Jones:
https://patchwork.kernel.org/patch/10367877/

Maybe we understand the problem better now to give more arguments why it makes
sense to create a mfd here?

Regards,
Matthias

> 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
>>
>