From: Mark Brown <broonie@kernel.org>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Fabrizio Castro <fabrizio.castro.jz@renesas.com>,
Rob Herring <robh+dt@kernel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
Conor Dooley <conor+dt@kernel.org>,
Magnus Damm <magnus.damm@gmail.com>,
linux-spi@vger.kernel.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-renesas-soc@vger.kernel.org,
Chris Paterson <Chris.Paterson2@renesas.com>,
Biju Das <biju.das@bp.renesas.com>,
Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Subject: Re: [PATCH 1/2] spi: renesas,rzv2m-csi: Add SPI Slave related properties
Date: Wed, 27 Sep 2023 11:21:54 +0200 [thread overview]
Message-ID: <ZRP0MpIHf67tfQJY@finisterre.sirena.org.uk> (raw)
In-Reply-To: <CAMuHMdUv8FFwkde8K3Ta8FEWrkkJ=9ZqbTi1EO8sRxVOhGtvzQ@mail.gmail.com>
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On Wed, Sep 27, 2023 at 11:10:58AM +0200, Geert Uytterhoeven wrote:
> On Wed, Sep 27, 2023 at 11:00 AM Mark Brown <broonie@kernel.org> wrote:
> > The description is clearly saying there is a chip select, _NO_CS seems
> > entirely inappropriate. It's not specified in the device tree because
> > when there's no chip select for a device it's a fundamental property of
> > how the device is controlled and we don't need any information beyond
> > the compatible.
> In host mode, it indeed doesn't matter, as you can have only a single
> device connected with SPI_NO_CS.
> In device mode, the device needs to know if it must monitor the chip
> select line or not.
> In hindsight, I should have kept the question I had written initially,
> but deleted after having read the documentation for the corresponding
> RZ/V2M register bits:
> What does it mean if this is false? That there is no chip select?
> So "spi-no-cs" would be the inverse of "renesas,csi-ss".
I see. Is there any control over what the chip select is when there is
one, in which case we could just look to see if there's one specified?
I'm a bit nervous about a generic property that maps onto _NO_CS since
it's likely that people will start using that in device bindings when
they shouldn't.
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next prev parent reply other threads:[~2023-09-27 9:22 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-26 21:08 [PATCH 0/2] Add RZ/V2M CSI slave support Fabrizio Castro
2023-09-26 21:08 ` [PATCH 1/2] spi: renesas,rzv2m-csi: Add SPI Slave related properties Fabrizio Castro
2023-09-27 7:59 ` Geert Uytterhoeven
2023-09-27 9:00 ` Mark Brown
2023-09-27 9:10 ` Geert Uytterhoeven
2023-09-27 9:21 ` Mark Brown [this message]
2023-09-27 9:44 ` Geert Uytterhoeven
2023-09-27 10:05 ` Mark Brown
2023-09-27 10:18 ` Fabrizio Castro
2023-09-27 10:22 ` Mark Brown
2023-09-27 9:43 ` Fabrizio Castro
2023-09-27 9:36 ` Fabrizio Castro
2023-09-27 8:56 ` Mark Brown
2023-09-27 9:40 ` Fabrizio Castro
2023-09-26 21:08 ` [PATCH 2/2] spi: rzv2m-csi: Add Slave mode support Fabrizio Castro
2023-09-27 9:02 ` Mark Brown
2023-09-27 9:12 ` Geert Uytterhoeven
2023-09-27 9:15 ` Mark Brown
2023-09-27 9:51 ` Geert Uytterhoeven
2023-09-27 10:05 ` Fabrizio Castro
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