Re: [PATCH v12 09/11] media: staging: dt-bindings: add Rockchip MIPI RX D-PHY yaml bindings

[Ezequiel Garcia <ezequiel@collabora.com>]

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@collabora.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@ff968000 {
                compatible = "rockchip,rk3399-mipi-dphy";
                reg = <0x0 0xff968000 0x0 0x8000>;
                rockchip,grf = <&grf>;
        };

        grf: syscon@ff770000 {
                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?

Thanks,
Ezequiel