Re: [PATCH 12/16] dt-bindings: media: Add DT bindings for TI CSI2RX driver

[Pratyush Yadav <p.yadav@ti.com>]

On 02/04/21 01:01PM, Laurent Pinchart wrote:
> On Thu, Apr 01, 2021 at 10:52:01AM -0500, Rob Herring wrote:
> > On Tue, Mar 30, 2021 at 11:03:44PM +0530, Pratyush Yadav wrote:
> > > TI's J721E uses the Cadence CSI2RX and DPHY peripherals to facilitate
> > > capture over a CSI-2 bus. The TI CSI2RX platform driver glues all the
> > > parts together.
> > > 
> > > Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
> > > ---
> > >  .../devicetree/bindings/media/ti,csi2rx.yaml  | 70 +++++++++++++++++++
> > >  1 file changed, 70 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/media/ti,csi2rx.yaml
> > > 
> > > diff --git a/Documentation/devicetree/bindings/media/ti,csi2rx.yaml b/Documentation/devicetree/bindings/media/ti,csi2rx.yaml
> > > new file mode 100644
> > > index 000000000000..ebd894364391
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/media/ti,csi2rx.yaml
> > > @@ -0,0 +1,70 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/media/ti,csi2rx.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: TI CSI2RX Wrapper Device Tree Bindings
> > > +
> 
> A description would be useful, especially given that the TRM doesn't
> mention "CSI2RX".

Ok.

> 
> > > +maintainers:
> > > +  - Pratyush Yadav <p.yadav@ti.com>
> > > +
> > > +properties:
> > > +  compatible:
> > > +    items:
> > > +      - const: ti,csi2rx
> > > +
> > > +  dmas:
> > > +    description: RX DMA Channel 0
> > 
> > items:
> >   - description: RX DMA Channel 0
> > 
> > Or just 'maxItems: 1'
> > 
> > > +
> > > +  dma-names:
> > > +    items:
> > > +      - const: rx0
> > > +
> > > +  reg:
> > > +    maxItems: 1
> > > +    description: Base address and size of the TI wrapper registers.
> > 
> > That's all 'reg' properties, drop 'description'.
> 
> According to SPRUIL1B, there are four register banks for the CSI_RX_IF,
> and two register banks for the DPHY_RX. What's your plan to support
> these ? Not everything need to be implemented at once, but backward
> compatibility need to be taken into account in the design.

The CSI_RX_IF0_ECC_AGGR_CFG register bank is for safety requirements. 
The driver does not use them. The CSI_RX_IF0_RX_SHIM_VBUSP_MMR_CSI2RXIF 
register bank is for the TI wrapper around the Cadence CSI2RX bridge 
that deals with DMA threads. This bank is what this binding is concerned 
with. The CSI_RX_IF0_VBUS2APB_WRAP_VBUS_APB_CSI2RX bank is for the 
Cadence CSI2RX bridge. The Cadence schema should deal with that. And 
lastly, I don't know what the CSI_RX_IF0_CP_INTD_CFG_INTD_CFG bank is 
for. The driver does not use it.

I don't forsee the first and last bank being used in Kernel, but if we 
want to be safe I can change maxItems to 3. Sounds good?

> 
> > > +
> > > +  power-domains:
> > > +    maxItems: 1
> > > +    description:
> > > +      PM domain provider node and an args specifier containing
> > > +      the device id value.
> > 
> > Drop.
> > 
> > > +
> > > +  ranges: true
> > > +
> > > +  "#address-cells":
> > > +    const: 2
> > > +
> > > +  "#size-cells":
> > > +    const: 2
> > > +
> > > +patternProperties:
> > > +  "csi-bridge@":
> > 
> > "^csi-bridge@"
> > 
> > > +    type: object
> > > +    description: CSI2 bridge node.
> > 
> > Just an empty node?
> 
> Even if the node is optional, it would be useful to include it in the
> example below, to show how it's supposed to be used.

It is not optional. It should be the Cadence CSI2RX bridge node. Will 
add it in the example. I also need to see if there is any way to make a 
patternProperty a required property.

> 
> > > +
> > > +required:
> > > +  - compatible
> > > +  - reg
> > > +  - dmas
> > > +  - dma-names
> > > +  - power-domains
> > > +  - "#address-cells"
> > > +  - "#size-cells"
> > > +
> > > +additionalProperties: false
> > > +
> > > +examples:
> > > +  - |
> > > +    #include <dt-bindings/soc/ti,sci_pm_domain.h>
> > > +
> > > +    ti_csi2rx0: ticsi2rx {
> > > +        compatible = "ti,csi2rx";
> > > +        dmas = <&main_udmap 0x4940>;
> > > +        dma-names = "rx0";
> > > +        reg = <0x0 0x4500000 0x0 0x1000>;
> > > +        power-domains = <&k3_pds 26 TI_SCI_PD_EXCLUSIVE>;
> > > +        #address-cells = <2>;
> > > +        #size-cells = <2>;
> > > +    };
> 
> -- 
> Regards,
> 
> Laurent Pinchart

-- 
Regards,
Pratyush Yadav
Texas Instruments Inc.