From: Rob Herring <robh@kernel.org>
To: Sam Protsenko <semen.protsenko@linaro.org>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jiri Slaby <jirislaby@kernel.org>,
Jaewon Kim <jaewon02.kim@samsung.com>,
Chanho Park <chanho61.park@samsung.com>,
David Virag <virag.david003@gmail.com>,
Youngmin Nam <youngmin.nam@samsung.com>,
devicetree@vger.kernel.org, linux-serial@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-samsung-soc@vger.kernel.org
Subject: Re: [PATCH v2 RESEND 1/5] dt-bindings: soc: samsung: Add Exynos USI bindings
Date: Fri, 3 Dec 2021 14:40:33 -0600 [thread overview]
Message-ID: <CAL_JsqLopqkOEWmnvMDWr2rBa5Dm3jf17soqVA=Jx5Hn9BDS_g@mail.gmail.com> (raw)
In-Reply-To: <CAPLW+4kGGk+umKTVRPNM7R=GaUQa31Uid=K+9ofq8w2mqzGAEA@mail.gmail.com>
On Fri, Dec 3, 2021 at 1:36 PM Sam Protsenko <semen.protsenko@linaro.org> wrote:
>
> On Tue, 30 Nov 2021 at 21:31, Rob Herring <robh@kernel.org> wrote:
> >
> > On Tue, Nov 30, 2021 at 01:13:21PM +0200, Sam Protsenko wrote:
> > > Add constants for choosing USIv2 configuration mode in device tree.
> > > Those are further used in USI driver to figure out which value to write
> > > into SW_CONF register. Also document USIv2 IP-core bindings.
> > >
> > > Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
> > > ---
> > > Changes in v2:
> > > - Combined dt-bindings doc and dt-bindings header patches
> > > - Added i2c node to example in bindings doc
> > > - Added mentioning of shared internal circuits
> > > - Added USI_V2_NONE value to bindings header
> > >
> > > .../bindings/soc/samsung/exynos-usi.yaml | 135 ++++++++++++++++++
> > > include/dt-bindings/soc/samsung,exynos-usi.h | 17 +++
> > > 2 files changed, 152 insertions(+)
> > > create mode 100644 Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
> > > create mode 100644 include/dt-bindings/soc/samsung,exynos-usi.h
> > >
> > > diff --git a/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml b/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
> > > new file mode 100644
> > > index 000000000000..a822bc62b3cd
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
> > > @@ -0,0 +1,135 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/soc/samsung/exynos-usi.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: Samsung's Exynos USI (Universal Serial Interface) binding
> > > +
> > > +maintainers:
> > > + - Sam Protsenko <semen.protsenko@linaro.org>
> > > + - Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
> > > +
> > > +description: |
> > > + USI IP-core provides selectable serial protocol (UART, SPI or High-Speed I2C).
> > > + USI shares almost all internal circuits within each protocol, so only one
> > > + protocol can be chosen at a time. USI is modeled as a node with zero or more
> > > + child nodes, each representing a serial sub-node device. The mode setting
> > > + selects which particular function will be used.
> > > +
> > > + Refer to next bindings documentation for information on protocol subnodes that
> > > + can exist under USI node:
> > > +
> > > + [1] Documentation/devicetree/bindings/serial/samsung_uart.yaml
> > > + [2] Documentation/devicetree/bindings/i2c/i2c-exynos5.txt
> > > + [3] Documentation/devicetree/bindings/spi/spi-samsung.txt
> > > +
> > > +properties:
> > > + $nodename:
> > > + pattern: "^usi@[0-9a-f]+$"
> > > +
> > > + compatible:
> > > + const: samsung,exynos-usi-v2
> >
> > Use SoC based compatibles.
> >
>
> In this particular case, I'd really prefer to have it like this. Most
> likely we'll only have USIv1 and USIv1 in the end, and I think that
> would be more clear to have USI version in compatible, rather than SoC
> name. Please let me know if you have a strong opinion on this one --
> if so I'll re-send.
Fine if you have some evidence the ratio of versions to SoC are much
more than 1:1 and the versions correspond to something (IOW, you
aren't making them up).
We went down the version # path with QCom and in the end about every
SoC had a different version.
>
> > > +
> > > + reg:
> > > + maxItems: 1
> > > +
> > > + clocks:
> > > + items:
> > > + - description: Bus (APB) clock
> > > + - description: Operating clock for UART/SPI/I2C protocol
> > > +
> > > + clock-names:
> > > + items:
> > > + - const: pclk
> > > + - const: ipclk
> > > +
> > > + ranges: true
> > > +
> > > + "#address-cells":
> > > + const: 1
> > > +
> > > + "#size-cells":
> > > + const: 1
> > > +
> > > + samsung,sysreg:
> > > + $ref: /schemas/types.yaml#/definitions/phandle-array
> > > + description:
> > > + Should be phandle/offset pair. The phandle to System Register syscon node
> > > + (for the same domain where this USI controller resides) and the offset
> > > + of SW_CONF register for this USI controller.
> > > +
> > > + samsung,mode:
> > > + $ref: /schemas/types.yaml#/definitions/uint32
> > > + description:
> > > + Selects USI function (which serial protocol to use). Refer to
> > > + <include/dt-bindings/soc/samsung,exynos-usi.h> for valid USI mode values.
> >
> > This seems to be redundant. Just check which child is enabled.
> >
>
> I think it's not that easy. Soon we'll have USIv1 support added, and
> that has some weird configurations, like having dual I2C mode (two
> child I2C nodes must be enabled) and UART+I2C mode, etc.
So you are going to turn around and make this an array? If you already
know you have changes, I'd rather review this all at once.
> Looks like it
> might take some not very elegant logic to figure out which exactly
> mode value should be written in SW_CONF register in that way, it's
> much easier to just specify mode in USI node. Also, that reflects
> hardware better: we actually write that specified mode to SW_CONF
> register.
You just have to compare the child node names or compatibles.
> Also, later we might want to be able to switch that mode via
> SysFS, e.g. for testing purposes. Current design seems to be better
> suited for some things like that.
The binding should have no impact on that. If for testing, use debugfs.
> Please let me know if you have a strong opinion on this one, or it's
> ok to leave it as is.
>
> All other comments are addressed and will be present in v3. Thanks for
> the review!
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next prev parent reply other threads:[~2021-12-03 20:42 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-30 11:13 [PATCH v2 RESEND 0/5] soc: samsung: Add USI driver Sam Protsenko
2021-11-30 11:13 ` [PATCH v2 RESEND 1/5] dt-bindings: soc: samsung: Add Exynos USI bindings Sam Protsenko
2021-11-30 17:43 ` Rob Herring
2021-11-30 20:04 ` Krzysztof Kozlowski
2021-12-01 16:19 ` Rob Herring
2021-12-02 11:00 ` Sam Protsenko
2021-12-02 20:44 ` Rob Herring
2021-12-03 18:39 ` Sam Protsenko
2021-11-30 19:31 ` Rob Herring
2021-12-03 19:35 ` Sam Protsenko
2021-12-03 20:40 ` Rob Herring [this message]
2021-12-04 0:18 ` Sam Protsenko
2021-12-04 11:31 ` Krzysztof Kozlowski
2021-12-04 11:28 ` Krzysztof Kozlowski
2021-12-04 14:27 ` Sam Protsenko
2021-11-30 11:13 ` [PATCH v2 RESEND 2/5] soc: samsung: Add USI driver Sam Protsenko
2021-12-01 10:52 ` Andy Shevchenko
2021-12-03 15:31 ` Sam Protsenko
2021-11-30 11:13 ` [PATCH v2 RESEND 3/5] tty: serial: samsung: Remove USI initialization Sam Protsenko
2021-12-01 10:54 ` Andy Shevchenko
2021-12-03 16:22 ` Sam Protsenko
2021-12-04 11:22 ` Krzysztof Kozlowski
2021-11-30 11:13 ` [PATCH v2 RESEND 4/5] tty: serial: samsung: Enable console as module Sam Protsenko
2021-11-30 11:13 ` [PATCH v2 RESEND 5/5] tty: serial: samsung: Fix console registration from module Sam Protsenko
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