Message-ID: <a86afcd38ce4243f86fddd1647129d64585e56d1.camel@mediatek.com>
Date:   Tue, 7 Jun 2022 10:31:21 +0800
From:   Rex-BC Chen <rex-bc.chen@...iatek.com>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Guillaume Ranquet <granquet@...libre.com>,
        Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        "David Airlie" <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        "Kishon Vijay Abraham I" <kishon@...com>,
        Vinod Koul <vkoul@...nel.org>, "Helge Deller" <deller@....de>,
        CK Hu <ck.hu@...iatek.com>, Jitao shi <jitao.shi@...iatek.com>
CC:     Markus Schneider-Pargmann <msp@...libre.com>,
        <dri-devel@...ts.freedesktop.org>,
        <linux-mediatek@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-phy@...ts.infradead.org>, <linux-fbdev@...r.kernel.org>
Subject: Re: [PATCH v10 01/21] dt-bindings: mediatek,dpi: Add DPINTF
 compatible

On Wed, 2022-05-25 at 13:55 +0200, AngeloGioacchino Del Regno wrote:
> Il 23/05/22 12:47, Guillaume Ranquet ha scritto:
> > From: Markus Schneider-Pargmann <msp@...libre.com>
> > 
> > DPINTF is similar to DPI but does not have the exact same feature
> > set
> > or register layouts.
> > 
> > DPINTF is the sink of the display pipeline that is connected to the
> > DisplayPort controller and encoder unit. It takes the same clocks
> > as
> > DPI.
> > 
> > Signed-off-by: Markus Schneider-Pargmann <msp@...libre.com>
> > Signed-off-by: Guillaume Ranquet <granquet@...libre.com>
> > ---
> >   .../bindings/display/mediatek/mediatek,dpi.yaml     | 13
> > ++++++++-----
> >   1 file changed, 8 insertions(+), 5 deletions(-)
> > 
> > diff --git
> > a/Documentation/devicetree/bindings/display/mediatek/mediatek,dpi.y
> > aml
> > b/Documentation/devicetree/bindings/display/mediatek/mediatek,dpi.y
> > aml
> > index dd2896a40ff0..6d9f6c11806e 100644
> > ---
> > a/Documentation/devicetree/bindings/display/mediatek/mediatek,dpi.y
> > aml
> > +++
> > b/Documentation/devicetree/bindings/display/mediatek/mediatek,dpi.y
> > aml
> > @@ -4,16 +4,16 @@
> >   $id: 
> > http://devicetree.org/schemas/display/mediatek/mediatek,dpi.yaml#
> >   $schema: http://devicetree.org/meta-schemas/core.yaml#
> >   
> > -title: mediatek DPI Controller Device Tree Bindings
> > +title: mediatek DPI/DPINTF Controller
> >   
> >   maintainers:
> >     - CK Hu <ck.hu@...iatek.com>
> >     - Jitao shi <jitao.shi@...iatek.com>
> >   
> >   description: |
> > -  The Mediatek DPI function block is a sink of the display
> > subsystem and
> > -  provides 8-bit RGB/YUV444 or 8/10/10-bit YUV422 pixel data on a
> > parallel
> > -  output bus.
> > +  The Mediatek DPI and DPINTF function blocks are a sink of the
> > display
> > +  subsystem and provides 8-bit RGB/YUV444 or 8/10/10-bit YUV422
> > pixel data on a
> > +  parallel output bus.
> >   
> >   properties:
> >     compatible:
> > @@ -23,6 +23,7 @@ properties:
> >         - mediatek,mt8173-dpi
> >         - mediatek,mt8183-dpi
> >         - mediatek,mt8192-dpi
> > +      - mediatek,mt8195-dpintf
> >   
> >     reg:
> >       maxItems: 1
> > @@ -35,12 +36,14 @@ properties:
> >         - description: Pixel Clock
> >         - description: Engine Clock
> >         - description: DPI PLL
> > +      - description: Optional CK CG Clock
> >   
> >     clock-names:
> >       items:
> >         - const: pixel
> >         - const: engine
> >         - const: pll
> > +      - const: ck_cg
> 
> This is my understanding on how the DisplayPort Interface clocks work
> on 8195:
> 
> The "engine" clock is for the *VPP Engine's DisplayPort ip/block*,
> "pll" is for TVD PLL divider selection
> "pixel" is the gate for the pixel clock to the connected display.
> 
> "ck_cg" is useless, as that's the parent of "pixel" (and will always
> be)... for
> example, on mt8195... check clk/mediatek/clk-mt8195-vdo0.c - the
> CLK_VDO0_DP_INTF0_DP_INTF clock already has CLK_TOP_EDP as its
> parent, hence
> enabling the first will enable the latter.
> 
> That said... you can most probably avoid adding the ck_cg clock, as
> if you try
> to turn that off while it's in use by its children, you'll be only
> decrementing
> a refcount, but no "real action" will ever take place.
> 
> 
> Regards,
> Angelo

Hello Chunfeng and Angelo,

ck_cg is a clock gate, and I try to remove it from drivers but it's
failed to enable dp_intf.

the block diagram is:
1. 26M->CLK_APMIXED_TVDPLL1(pll)->CLK_TOP_EDP(pixel)-
>CLK_VDO0_DP_INTF0_DP_INTF(ck_cg)->dp_intf

2. VDOSYS clock->CLK_VDO0_DP_INTF0(engine)->dp_intf

"engine" and "ck_cg" are all clock gates which control the clock source
input to dp_intf.

Maybe we just need to rename it?
If so, what name do you think we should modify?

BRs,
Bo-Chen

> 
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