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

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Date:   Mon, 19 Nov 2018 15:14:07 +0100
From:   Marek Vasut <marek.vasut@...il.com>
To:     Boris Brezillon <boris.brezillon@...tlin.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 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.

-- 
Best regards,
Marek Vasut