From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marek Vasut Subject: Re: [PATCH 2/2] dt-binding: spi: Document Renesas R-Car RPC controller bindings Date: Mon, 19 Nov 2018 23:22:45 +0100 Message-ID: <9e217c7c-6626-d683-2d99-0b7571043b3b@gmail.com> References: <1542621690-10229-1-git-send-email-masonccyang@mxic.com.tw> <1542621690-10229-3-git-send-email-masonccyang@mxic.com.tw> <629a5d6f-5c13-9b24-1c21-461d09f1aa8a@gmail.com> <20181119151009.490413d9@bbrezillon> <20181119154338.2dfa7a5a@bbrezillon> <4c0683d3-fe9d-5a10-6f5c-4774024cb12a@gmail.com> <20181119162127.71d0665d@bbrezillon> <3f791a3c-4a2e-5d43-1026-e1e7b879b562@gmail.com> <20181119231954.333699f4@bbrezillon> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: Mason Yang , broonie@kernel.org, tpiepho@impinj.com, linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org, linux-renesas-soc@vger.kernel.org, Simon Horman , juliensu@mxic.com.tw, Geert Uytterhoeven , zhengxunli@mxic.com.tw To: Boris Brezillon Return-path: In-Reply-To: <20181119231954.333699f4@bbrezillon> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-spi.vger.kernel.org On 11/19/2018 11:19 PM, Boris Brezillon wrote: > On Mon, 19 Nov 2018 23:11:31 +0100 > Marek Vasut wrote: > >> On 11/19/2018 04:21 PM, Boris Brezillon wrote: >>> On Mon, 19 Nov 2018 16:12:41 +0100 >>> Marek Vasut wrote: >>> >>>> On 11/19/2018 03:43 PM, Boris Brezillon wrote: >>>>> On Mon, 19 Nov 2018 15:14:07 +0100 >>>>> Marek Vasut wrote: >>>>> >>>>>> On 11/19/2018 03:10 PM, Boris Brezillon wrote: >>>>>>> On Mon, 19 Nov 2018 14:49:31 +0100 >>>>>>> Marek Vasut 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 >>>>>>>>> --- >>>>>>>>> .../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. >>>> >>>> Do you even need a dedicated property ? I think you can decide purely on >>>> what node is hanging under the controller (jedec spi nor or cfi nor). >>> >>> Yes, that could work if they have well-known compatibles. As soon as >>> people start using flash-specific compats (like some people do for >>> their SPI NORs) it becomes a maintenance burden. >> >> Which, on this controller, is very likely never gonna happen. Once it >> does , we can add a custom property. >> >>>>> 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... >>>> >>>> I'd definitely prefer a single driver. >>>> >>> >>> Where would you put this driver? I really don't like the idea of having >>> MTD drivers spread over the tree. Don't know what's Mark's opinion on >>> this matter. >> >> Well, it's both CFI (hyperflash) and SF (well, SPI flash) controller, so >> where would this go ? >> > > The spi-mem layer is in drivers/spi/ so it could go in drivers/spi/ > (spi-mem controller) or drivers/mtd/ (CFI controller). drivers/mtd is probably a better option, since it's not a generic SPI controller. -- Best regards, Marek Vasut