From: Conor Dooley <conor@kernel.org>
To: Marco Felsch <m.felsch@pengutronix.de>
Cc: conor.dooley@microchip.com, v.georgiev@metrotek.ru,
mdf@kernel.org, hao.wu@intel.com, yilun.xu@intel.com,
trix@redhat.com, robh+dt@kernel.org,
krzysztof.kozlowski+dt@linaro.org, linux-fpga@vger.kernel.org,
devicetree@vger.kernel.org, kernel@pengutronix.de
Subject: Re: [PATCH] dt-bindings: fpga: microchip,mpf-spi-fpga-mgr: document CPOL/CPHA support
Date: Fri, 23 Feb 2024 19:13:57 +0000 [thread overview]
Message-ID: <20240223-polio-debating-241fc4ab2262@spud> (raw)
In-Reply-To: <20240222200230.ulhguouu37nm6inu@pengutronix.de>
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On Thu, Feb 22, 2024 at 09:02:30PM +0100, Marco Felsch wrote:
> On 24-02-22, Conor Dooley wrote:
> > On Wed, Feb 21, 2024 at 08:12:47PM +0100, Marco Felsch wrote:
> > > Microchip FPGAs can communicate in different modes, so document them to
> > > avoid dt-validate warnings.
> >
> > Are you sure it can "communicate in different modes"?
>
> No I'm not but I didn't found an overview within the FPGA datasheet [1]
> which modes are supported. What I did found was an note which says:
>
> """
> 1. Parameters are referenced to the active edge of SCK, which depends on
> the configured SPI protocol (for example, Motorola SPI mode uses rising
> edge as active edge if SPO = 0)
> """
>
> Therefore I thought that this can be configured somehow differently.
>
> [1] https://www.microsemi.com/document-portal/doc_view/136519-ds0141-polarfire-fpga-datasheet
>
> > The documentation actually says "Motorla SPI Mode 3 is required to
> > communicate with M2S, M2GL, and MPF devices using dedicated system
> > controller SPI port" with mode 3 being SPO = SPH = 1:
> > https://www.microsemi.com/document-portal/doc_view/137543-spi-directc-sp1-v2-0-user-guide
>
> Thanks for the Pointer, there are plenty documents for the Polarfire
> FPGA.
>
> > I suspect the answer is that it can actually communicate in different
> > modes (because I don't recall setting those options), but the binding
> > should enforce the correct way of doing it IMO.
>
> Sure, I will rephrase my commit message to:
>
> """
> dt-bindings: fpga: microchip,mpf-spi-fpga-mgr: document CPOL/CPHA
>
> Using the dedicated system controller SPI port requires Motorola SPI
> Mode 3 according the SPI-DirectC v2.0 User Guid [1]. So require the
> spi-cpol and spi-cpha to be set.
>
> [1] https://www.microsemi.com/document-portal/doc_view/137543-spi-directc-sp1-v2-0-user-guide
> """
You say require here, but don't actually make them required.
I think we probably should actually make them required, since the docs
say they should be used, but I'd like to look at it a bit more though
before that, since it does work on the setup I had without them.
I'd say do s/require/allow/ and I'll try to do some testing as to
whether we should actually mark the properties as required.
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Cheers,
Conor.
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prev parent reply other threads:[~2024-02-23 19:14 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-21 19:12 [PATCH] dt-bindings: fpga: microchip,mpf-spi-fpga-mgr: document CPOL/CPHA support Marco Felsch
2024-02-22 17:23 ` Conor Dooley
2024-02-22 20:02 ` Marco Felsch
2024-02-23 19:13 ` Conor Dooley [this message]
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