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Message-ID: <935b3413-7a6f-79c8-aa74-2dae2fec62a0@socionext.com>
Date: Sat, 19 Nov 2022 01:41:20 +0900
From: Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
To: Mark Brown <broonie@...nel.org>
Cc: Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
linux-spi@...r.kernel.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: spi: Add Socionext F_OSPI controller
bindings
On 2022/11/19 0:36, Mark Brown wrote:
> On Fri, Nov 18, 2022 at 11:16:22PM +0900, Kunihiko Hayashi wrote:
>> On 2022/11/18 20:39, Mark Brown wrote:
>>> On Fri, Nov 18, 2022 at 09:59:03AM +0900, Kunihiko Hayashi wrote:
>
>>>> + socionext,cs-start-cycle:
>>>> + socionext,cs-end-cycle:
>>>> + socionext,cs-deassert-clk-cycle:
>
>>> These are all generic SPI properties so we should add them
>>> generically, on the device rather than the controller since this
>>> is something that might vary per client device. There was also a
>>> core function spi_set_cs_timing() which was in earlier versions
>>> and is about to get reintroduced.
>
>> So I understand you mean that these properties should be defined like
>> spi-peripheral-props.yaml for the devices.
>
>> If yes, I'll drop these properties once and define our vendor-specific
>> "peripheral-props" in the next series.
>
> Yes, sounds good.
Okay, I'll send simple one in v2.
>>>> + $ref: /schemas/types.yaml#/definitions/uint32-array
>>>> + items:
>>>> + - description: the number of bytes to transfer
>>>> + maximum: 4
>>>> + - description: value to transfer
>>>> + default: 0
>>>> + - description: bit-width to transfer
>>>> + enum: [0, 1, 2, 4, 8]
>
>>> This is also something SPI device should set up, as far as I can
>>> tell this should be set vis spi_mem_op.dummy.nbytes.
>
>> Yes, but the controller also supports dummy cycles, and can send
>> extra bytes before the dummy cycles.
>
> Ah, so this is some additional thing on top of dummy cycles? I'd
> not realised that. It probably wants to be added into spi-mem I
> guess.
Yes, however, it's tough to handle with spi-mem and I don't have
any use case, so drop it.
>>>> + socionext,data-swap-2byte:
>>>> + description:
>>>> + Indicates swap byte order per 2-bytes.
>>>> + type: boolean
>>>
>>>> + socionext,data-swap-4byte:
>>>> + description:
>>>> + Indicates swap byte order per 4-bytes.
>>>> + type: boolean
>
>>> Again these should be set by the device. I think these should be
>>> set based on a combination of bits per word and if the host is in
>>> big endian or little endian mode.
>
>> I see. This feature is complicated to use, so I'll not add it here.
>
> That also works, someone can always add additional support later
> when they have a concrete use case.
I understand.
Thank you,
---
Best Regards
Kunihiko Hayashi
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