Message-ID: <3869290.WS1K4CcMg6@phil>
Date:   Tue, 07 Jan 2020 23:25:17 +0100
From:   Heiko Stuebner <heiko@...ech.de>
To:     Ezequiel Garcia <ezequiel@...labora.com>
Cc:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Helen Koike <helen.koike@...labora.com>,
        linux-rockchip@...ts.infradead.org, mark.rutland@....com,
        devicetree@...r.kernel.org, eddie.cai.linux@...il.com,
        mchehab@...nel.org, gregkh@...uxfoundation.org,
        andrey.konovalov@...aro.org, linux-kernel@...r.kernel.org,
        tfiga@...omium.org, robh+dt@...nel.org, hans.verkuil@...co.com,
        sakari.ailus@...ux.intel.com, joacim.zetterling@...il.com,
        kernel@...labora.com, linux-media@...r.kernel.org,
        jacob-chen@...wrt.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v12 09/11] media: staging: dt-bindings: add Rockchip MIPI RX D-PHY yaml bindings

Am Dienstag, 7. Januar 2020, 23:03:54 CET schrieb Ezequiel Garcia:
> On Tue, 2020-01-07 at 22:30 +0100, Heiko Stübner wrote:
> > Hi Ezequiel,
> > 
> > Am Dienstag, 7. Januar 2020, 14:20:10 CET schrieb Ezequiel Garcia:
> > > Hi Heiko, Laurent,
> > > 
> > > On Tue, 2020-01-07 at 10:28 +0100, Heiko Stübner wrote:
> > > > Am Dienstag, 7. Januar 2020, 03:37:21 CET schrieb Laurent Pinchart:
> > > > > On Mon, Jan 06, 2020 at 11:06:12PM -0300, Ezequiel Garcia wrote:
> > > > > > On Tue, 2020-01-07 at 02:10 +0200, Laurent Pinchart wrote:
> > > > > > > Hi Helen,
> > > > > > > 
> > > > > > > Thank you for the patch.
> > > > > > > 
> > > > > > > On Fri, Dec 27, 2019 at 05:01:14PM -0300, Helen Koike wrote:
> > > > > > > > Add yaml DT bindings for Rockchip MIPI D-PHY RX
> > > > > > > > 
> > > > > > > > This was tested and verified with:
> > > > > > > > mv drivers/staging/media/phy-rockchip-dphy/Documentation/devicetree/bindings/phy/rockchip-mipi-
> > > > > > > > dphy.yaml  Documentation/devicetree/bindings/phy/
> > > > > > > > make dt_binding_check DT_SCHEMA_FILES=Documentation/devicetree/bindings/phy/rockchip-mipi-dphy.yaml
> > > > > > > > make dtbs_check DT_SCHEMA_FILES=Documentation/devicetree/bindings/phy/rockchip-mipi-dphy.yaml
> > > > > > > > 
> > > > > > > > Signed-off-by: Helen Koike <helen.koike@...labora.com>
> > > > > > > > 
> > > > > > > > ---
> > > > > > > > 
> > > > > > > > Changes in v12:
> > > > > > > > - The commit replaces the following commit in previous series named
> > > > > > > > media: staging: dt-bindings: Document the Rockchip MIPI RX D-PHY bindings
> > > > > > > > This new patch adds yaml binding and was verified with
> > > > > > > > make dtbs_check and make dt_binding_check
> > > > > > > > 
> > > > > > > > Changes in v11: None
> > > > > > > > Changes in v10:
> > > > > > > > - unsquash
> > > > > > > > 
> > > > > > > > Changes in v9:
> > > > > > > > - fix title division style
> > > > > > > > - squash
> > > > > > > > - move to staging
> > > > > > > > 
> > > > > > > > Changes in v8: None
> > > > > > > > Changes in v7:
> > > > > > > > - updated doc with new design and tested example
> > > > > > > > 
> > > > > > > >  .../bindings/phy/rockchip-mipi-dphy.yaml      | 75 +++++++++++++++++++
> > > > > > > >  1 file changed, 75 insertions(+)
> > > > > > > >  create mode 100644 drivers/staging/media/phy-rockchip-dphy/Documentation/devicetree/bindings/phy/rockchip-mipi-dphy.yaml
> > > > > > > > 
> > > > > > > > diff --git a/drivers/staging/media/phy-rockchip-dphy/Documentation/devicetree/bindings/phy/rockchip-mipi-dphy.yaml
> > > > > > > > b/drivers/staging/media/phy-
> > > > > > > > rockchip-dphy/Documentation/devicetree/bindings/phy/rockchip-mipi-dphy.yaml
> > > > > > > > new file mode 100644
> > > > > > > > index 000000000000..af97f1b3e005
> > > > > > > > --- /dev/null
> > > > > > > > +++ b/drivers/staging/media/phy-rockchip-dphy/Documentation/devicetree/bindings/phy/rockchip-mipi-dphy.yaml
> > > > > > > > @@ -0,0 +1,75 @@
> > > > > > > > +# SPDX-License-Identifier: (GPL-2.0+ OR MIT)
> > > > > > > > +%YAML 1.2
> > > > > > > > +---
> > > > > > > > +$id: http://devicetree.org/schemas/phy/rockchip-mipi-dphy.yaml#
> > > > > > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > > > > > +
> > > > > > > > +title: Rockchip SoC MIPI RX0 D-PHY Device Tree Bindings
> > > > > > > 
> > > > > > > Should this be s/RX0/RX/ ? Or do you expect different bindings for RX1 ?
> > > > > > 
> > > > > > The driver currently only supports RX0, but I think you are right,
> > > > > > it should say RX here. This binding could be extended for RX1.
> > > > > > 
> > > > > > > Looking at the PHY driver, it seems to handle all PHYs with a single
> > > > > > > struct device. Should we thus use #phy-cells = <1> to select the PHY ?
> > > > > > 
> > > > > > I am not following this. The driver handles just one PHY. Each PHY
> > > > > > should have its own node.
> > > > > 
> > > > > Looking at the registers, it seems that the different PHYs are
> > > > > intertwined and we would could have trouble handling the different PHYs
> > > > > with different DT nodes and thus struct device instances.
> > > > 
> > > > I have to confess to not following _ALL_ of the threads, so may say
> > > > something stupid, but I don't think the PHYs are intertwined so much.
> > > > 
> > > > Where RX0 is controlled from the "General Register Files" alone
> > > > [register dumping ground for soc designers], the TX1RX1-phy
> > > > actually gets controlled from inside the dsi1 register area it seems.
> > > > 
> > > > So in my previous (still unsucessful) tests, I was rolling with something like
> > > > https://github.com/mmind/linux-rockchip/commit/e0d4b03976d2aab85a8c1630be937ea003b5df88
> > > > 
> > > > With the actual "logic" picked from the vendor kernel, that just double-
> > > > maps the dsi1-registers in both dsi and dphy driver, which was strange.
> > > > 
> > > > 
> > > 
> > > Describing each PHY in its own device node (as we currently do)
> > > results in:
> > > 
> > >         mipi_dphy_tx1rx1: mipi-dphy-tx1rx1@...68000 {
> > >                 compatible = "rockchip,rk3399-mipi-dphy";
> > >                 reg = <0x0 0xff968000 0x0 0x8000>;
> > >                 rockchip,grf = <&grf>;
> > >         };
> > 
> > 0xff968000 actually really is the dsi1 controller, so we'll already
> > have a node for that area. That is the reason I went that way to make
> > the rockchip-dsi optionally also behave as phy-provider.
> > 
> > So when it's used in combination with drm and a panel or so it will
> > behave as dsi controller, but when requested via the phy-framework
> > it will expose the dphy functionality.
> > 
> 
> Hm, and will this driver also support RX1?

what is RX1 in your book? :-)

According to the TRM the rk3399 has 3 DPHYs,
tx0 - connected exclusively to dsi0
      (this is handled internally by the dw-mipi-dsi driver with controls
       in the dsi0 register space)
rx0 - connected exclusively to isp0
      (this is handled by the individual dphy driver from Helen's series)
tx1rx1 - shared between dsi1 and isp1
      (again inside the dsi1 register space)


> 
> > 
> > >         grf: syscon@...70000 {
> > >                 mipi_dphy_rx0: mipi-dphy-rx0 {
> > >                         compatible = "rockchip,rk3399-mipi-dphy";
> > >                 };
> > >         };
> > > 
> > > Which is mildly ugly, as it uses two mechanism to describe
> > > the GRF resource. In addition, the driver will then _infer_
> > > which device node is RX0 and which is TX1RX1, from this.
> > > 
> > > Perhaps Laurent's proposal, describing each PHY explicitly,
> > > would be cleaner?
> > 
> > so I really think we shouldn't merge these two things together,
> > especially to not break the dsi1 controller part.
> > 
> 
> I don't think it would necesarily break the dsi1 controller part.
> 
> You can declare both device nodes as sharing the address region,
> and then the driver can request the I/O resource only when it needs to,
> i.e. in the PHY .init hook.

dsi1 is of course a dw-mipi-dsi one, which in turn shares a common bridge
driver over multiple variants (non-rockchip), which expects its registers
mapped during probe.

I think it would not really work well if you need to make the whole world
follow that idea ;-) .


Hence my approach with exposing the phy interface from the dsi driver.
If you look at the dts part, it also just looks like it should be ... as
a regular phy:
	https://github.com/mmind/linux-rockchip/blob/wip/tc358749/arch/arm64/boot/dts/rockchip/rk3399.dtsi#L1764

And on the driver side there is even some short circuit protection.
When used as phy, it won't allow to be used as a component and
vice versa.


> It's not super nice, but there's no real reason two devices
> can't share an I/O memory resource.

Counter argument, devicetree is not a means to handle Linux
peculiarites - instead it should describe the hardware ...
and the area there _is_ the dsi1 controller ;-)

Heiko

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