From: Boris Brezillon <boris.brezillon@bootlin.com>
To: Marek Vasut <marek.vasut@gmail.com>
Cc: Mason Yang <masonccyang@mxic.com.tw>,
broonie@kernel.org, tpiepho@impinj.com,
linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org,
linux-renesas-soc@vger.kernel.org,
Simon Horman <horms@verge.net.au>,
juliensu@mxic.com.tw,
Geert Uytterhoeven <geert+renesas@glider.be>,
zhengxunli@mxic.com.tw
Subject: Re: [PATCH 2/2] dt-binding: spi: Document Renesas R-Car RPC controller bindings
Date: Mon, 19 Nov 2018 23:31:14 +0100 [thread overview]
Message-ID: <20181119233114.3c5075e7@bbrezillon> (raw)
In-Reply-To: <90f42104-a6bd-54e7-959c-ebb906c6019a@gmail.com>
On Mon, 19 Nov 2018 23:29:00 +0100
Marek Vasut <marek.vasut@gmail.com> wrote:
> On 11/19/2018 11:25 PM, Boris Brezillon wrote:
> > On Mon, 19 Nov 2018 23:22:45 +0100
> > Marek Vasut <marek.vasut@gmail.com> wrote:
> >
> >> On 11/19/2018 11:19 PM, Boris Brezillon wrote:
> >>> On Mon, 19 Nov 2018 23:11:31 +0100
> >>> Marek Vasut <marek.vasut@gmail.com> wrote:
> >>>
> >>>> On 11/19/2018 04:21 PM, Boris Brezillon wrote:
> >>>>> On Mon, 19 Nov 2018 16:12:41 +0100
> >>>>> Marek Vasut <marek.vasut@gmail.com> wrote:
> >>>>>
> >>>>>> On 11/19/2018 03:43 PM, Boris Brezillon wrote:
> >>>>>>> On Mon, 19 Nov 2018 15:14:07 +0100
> >>>>>>> Marek Vasut <marek.vasut@gmail.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@gmail.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@mxic.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.
> >>>>>>
> >>>>>> 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.
> >>
> >
> > No, spi-mem controller drivers should go in drivers/spi/ even if they
> > don't implement the generic SPI interface (it's allowed to only
> > implement the spi_mem interface).
>
> Except this is not only SPI MEM controller, this is also hyperflash
> (that is, CFI) controller. It can drive both types of chips. Thus , I
> think it fits better in drivers/mtd/ .
>
Okay, then I guess we need an ack from Mark on that.
next prev parent reply other threads:[~2018-11-19 22:31 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-19 10:01 [PATCH 0/2] spi: Add Renesas R-Car D3 RPC SPI driver Mason Yang
2018-11-19 10:01 ` [PATCH 1/2] spi: Add Renesas R-Car RPC SPI controller driver Mason Yang
2018-11-19 14:12 ` Marek Vasut
2018-11-19 15:27 ` Mark Brown
2018-11-19 22:10 ` Marek Vasut
2018-11-20 13:26 ` Mark Brown
2018-11-20 13:33 ` Marek Vasut
[not found] ` <OF4FAD10C5.F4F6D29B-ON4825834B.001FAB40-4825834B.00289635@mxic.com.tw>
2018-11-20 13:09 ` Marek Vasut
2018-11-20 13:32 ` Boris Brezillon
2018-11-20 13:35 ` Marek Vasut
[not found] ` <OF5B1A3AE4.2DEECF37-ON4825834E.00031E97-4825834E.00042D72@mxic.com.tw>
2018-11-23 13:34 ` Marek Vasut
2018-11-20 2:04 ` kbuild test robot
2018-11-20 5:49 ` kbuild test robot
2018-11-20 8:01 ` Geert Uytterhoeven
2018-11-20 8:10 ` Boris Brezillon
2018-11-19 10:01 ` [PATCH 2/2] dt-binding: spi: Document Renesas R-Car RPC controller bindings Mason Yang
2018-11-19 13:49 ` Marek Vasut
2018-11-19 14:10 ` Boris Brezillon
2018-11-19 14:14 ` Marek Vasut
2018-11-19 14:43 ` Boris Brezillon
2018-11-19 15:12 ` Marek Vasut
2018-11-19 15:21 ` Boris Brezillon
2018-11-19 22:11 ` Marek Vasut
2018-11-19 22:19 ` Boris Brezillon
2018-11-19 22:22 ` Marek Vasut
2018-11-19 22:25 ` Boris Brezillon
2018-11-19 22:29 ` Marek Vasut
2018-11-19 22:31 ` Boris Brezillon [this message]
[not found] ` <OFDD04CD59.10199EDD-ON4825834B.001E1390-4825834B.001F65DD@mxic.com.tw>
2018-11-20 12:57 ` Marek Vasut
[not found] ` <OF26D8352D.B4B02BBE-ON4825834C.00043726-4825834C.0004E2F7@mxic.com.tw>
2018-11-21 1:51 ` Marek Vasut
2018-11-20 8:07 ` Geert Uytterhoeven
2018-11-20 13:56 ` kbuild test robot
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