linux-kernel - Re: [PATCH 2/2] dt-binding: spi: Document Renesas R-Car RPC controller bindings

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Message-ID: <20181119154338.2dfa7a5a@bbrezillon>
Date:   Mon, 19 Nov 2018 15:43:38 +0100
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Marek Vasut <marek.vasut@...il.com>
Cc:     Mason Yang <masonccyang@...c.com.tw>, broonie@...nel.org,
        tpiepho@...inj.com, linux-kernel@...r.kernel.org,
        linux-spi@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        Simon Horman <horms@...ge.net.au>, juliensu@...c.com.tw,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        zhengxunli@...c.com.tw
Subject: Re: [PATCH 2/2] dt-binding: spi: Document Renesas R-Car RPC
 controller bindings

On Mon, 19 Nov 2018 15:14:07 +0100
Marek Vasut <marek.vasut@...il.com> wrote:

> On 11/19/2018 03:10 PM, Boris Brezillon wrote:
> > On Mon, 19 Nov 2018 14:49:31 +0100
> > Marek Vasut <marek.vasut@...il.com> wrote:
> >   
> >> On 11/19/2018 11:01 AM, Mason Yang wrote:  
> >>> Document the bindings used by the Renesas R-Car D3 RPC controller.
> >>>
> >>> Signed-off-by: Mason Yang <masonccyang@...c.com.tw>
> >>> ---
> >>>  .../devicetree/bindings/spi/spi-renesas-rpc.txt    | 33 ++++++++++++++++++++++
> >>>  1 file changed, 33 insertions(+)
> >>>  create mode 100644 Documentation/devicetree/bindings/spi/spi-renesas-rpc.txt
> >>>
> >>> diff --git a/Documentation/devicetree/bindings/spi/spi-renesas-rpc.txt b/Documentation/devicetree/bindings/spi/spi-renesas-rpc.txt
> >>> new file mode 100644
> >>> index 0000000..8286cc8
> >>> --- /dev/null
> >>> +++ b/Documentation/devicetree/bindings/spi/spi-renesas-rpc.txt
> >>> @@ -0,0 +1,33 @@
> >>> +Renesas R-Car D3 RPC controller Device Tree Bindings
> >>> +----------------------------------------------------
> >>> +
> >>> +Required properties:
> >>> +- compatible: should be "renesas,rpc-r8a77995"
> >>> +- #address-cells: should be 1
> >>> +- #size-cells: should be 0
> >>> +- reg: should contain 2 entries, one for the registers and one for the direct
> >>> +       mapping area
> >>> +- reg-names: should contain "rpc_regs" and "dirmap"
> >>> +- interrupts: interrupt line connected to the RPC SPI controller    
> >>
> >> Do you also plan to support the RPC HF mode ? And if so, how would that
> >> look in the bindings ?  
> > 
> > Not sure this approach is still accepted, but that's how we solved the
> > problem for the flexcom block [1].
> > 
> > [1]https://elixir.bootlin.com/linux/v4.20-rc3/source/Documentation/devicetree/bindings/mfd/atmel-flexcom.txt  
> 
> That looks pretty horrible.
> 
> In U-Boot we check whether the device hanging under the controller node
> is JEDEC SPI flash or CFI flash and based on that decide what the config
> of the controller should be (SPI or HF). Not sure that's much better,but
> at least it doesn't need extra nodes which do not really represent any
> kind of real hardware.
> 

The subnodes are not needed, you can just have a property that tells in
which mode the controller is supposed to operate, and the MFD would
create a sub-device that points to the same device_node. Or we can have
a single driver that decides what to declare (a spi_controller or flash
controller), but you'd still have to decide where to place this
driver...