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Message-ID: <20220704131810.kabkuy6e4qmhfm3n@mobilestation>
Date: Mon, 4 Jul 2022 16:18:10 +0300
From: Serge Semin <fancer.lancer@...il.com>
To: Brad Larson <brad@...sando.io>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
Linux ARM <linux-arm-kernel@...ts.infradead.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
linux-mmc <linux-mmc@...r.kernel.org>,
Adrian Hunter <adrian.hunter@...el.com>,
Al Cooper <alcooperx@...il.com>,
Andy Shevchenko <andy.shevchenko@...il.com>,
Arnd Bergmann <arnd@...db.de>, blarson@....com,
Catalin Marinas <catalin.marinas@....com>,
Gabriel Somlo <gsomlo@...il.com>, gerg@...ux-m68k.org,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Lee Jones <lee.jones@...aro.org>,
Mark Brown <broonie@...nel.org>,
Masahiro Yamada <yamada.masahiro@...ionext.com>,
Philipp Zabel <p.zabel@...gutronix.de>,
Pratyush Yadav <p.yadav@...com>,
Randy Dunlap <rdunlap@...radead.org>,
Rob Herring <robh+dt@...nel.org>, samuel@...lland.org,
suravee.suthikulpanit@....com,
Tom Lendacky <thomas.lendacky@....com>,
Ulf Hansson <ulf.hansson@...aro.org>,
Will Deacon <will@...nel.org>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@...r.kernel.org>
Subject: Re: [PATCH v5 04/15] dt-bindings: spi: dw: Add AMD Pensando Elba SoC
SPI Controller bindings
On Sun, Jul 03, 2022 at 04:58:09PM -0700, Brad Larson wrote:
> Hi Sergey,
>
> On Tue, Jun 21, 2022 at 3:12 AM Serge Semin <fancer.lancer@...il.com> wrote:
> >
> > On Tue, Jun 21, 2022 at 09:00:36AM +0200, Krzysztof Kozlowski wrote:
> > > On 20/06/2022 22:04, Serge Semin wrote:
> > > > On Mon, Jun 20, 2022 at 09:46:25PM +0200, Krzysztof Kozlowski wrote:
> > > >> On 20/06/2022 21:30, Serge Semin wrote:
> > > >>> On Mon, Jun 13, 2022 at 12:56:47PM -0700, Brad Larson wrote:
> > > >>>> From: Brad Larson <blarson@....com>
> > > >>>>
> > > >>>> The AMD Pensando Elba SoC has integrated the DW APB SPI Controller
> > > >>>>
> > > >>>> Signed-off-by: Brad Larson <blarson@....com>
> > > >>>> ---
> > > >>>> Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.yaml | 2 ++
> > > >>>> 1 file changed, 2 insertions(+)
> > > >>>>
> > > >>>> diff --git a/Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.yaml b/Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.yaml
> > > >>>> index e25d44c218f2..2a55b947cffc 100644
> > > >>>> --- a/Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.yaml
> > > >>>> +++ b/Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.yaml
> > > >>>> @@ -73,6 +73,8 @@ properties:
> > > >>>> - renesas,r9a06g032-spi # RZ/N1D
> > > >>>> - renesas,r9a06g033-spi # RZ/N1S
> > > >>>> - const: renesas,rzn1-spi # RZ/N1
> > > >>>
> > > >>>> + - description: AMD Pensando Elba SoC SPI Controller
> > > >>>> + const: amd,pensando-elba-spi
> > > >>>
> > > >>> Not enough. The driver requires to have a phandle reference to the
> > > >>> Pensando System Controller. So the property like
> > > >>> "amd,pensando-elba-syscon" is also needed to be added to the DT schema
> > > >>> otherwise should the dt-schema tool correctly handle the
> > > >>> "unevaluatedProperties: false" setting (Rob says it isn't fully
> > > >>> supported at the moment), the dtbs_check procedure will fail on your
> > > >>> dts evaluation.
> > > >>
> > > >
> > > >> The property was here before, now removed, so I assume it was also
> > > >> removed from the driver and DTS. Isn't that the case?
> > > >
> > > > Ah, the property has been indeed removed. The driver now searches for
> > > > the system controller by the next compatible string:
> > > > "amd,pensando-elba-syscon" using the
> > > > syscon_regmap_lookup_by_compatible() method. My mistake. Sorry for the
> > > > noise.
> > > >
> >
> > > > * Though personally I'd prefer to have a property with the phandle
> > > > reference in order to signify the connection between the system controller
> > > > and the SPI-controller. Otherwise the implicit DT bindings like having
> > > > the "amd,pensando-elba-syscon"-compatible syscon gets to be
> > > > hidden behind the DT scene. But seeing we have already got the Microsemi
> > > > platform with such semantic, I can't insist on fixing this.
> > >
> > > I agree entirely, this should be explicit syscon-type property. Looking
> > > up for compatibles:
> > > - creates hidden (not expressed via bindings) dependency between nodes,
> > > - is not portable and several people struggled with it later and needed
> > > backward-compatible code (many examples, let's just give recent one: [1])
> > >
> > >
> > > [1]
> > > https://lore.kernel.org/all/20220619151225.209029-10-tmaimon77@gmail.com/
> >
> > Seems even more reasonable now. Thanks for providing a bright example
> > justifying the property-based approach.
> >
> > @Brad, could you get back the property with a phandle to the syscon
> > DT-node? (No need in adding the CS CSR address as the phandle argument,
> > just a phandle.)
>
> Replying to the sequence of review inputs. The below change to
> version 5 brings back the phandle without the earlier argument that
> complicated the binding (was the motivation for moving in this
> direction in earlier version). Passes dtbs_check.
>
> --- a/drivers/spi/spi-dw-mmio.c
> +++ b/drivers/spi/spi-dw-mmio.c
> @@ -285,12 +285,17 @@ static void dw_spi_elba_set_cs(struct spi_device
> *spi, bool enable)
> static int dw_spi_elba_init(struct platform_device *pdev,
> struct dw_spi_mmio *dwsmmio)
> {
> + struct device_node *np = pdev->dev.of_node;
> + struct device_node *node;
> struct dw_spi_elba *dwselba;
> struct regmap *regmap;
>
> - regmap = syscon_regmap_lookup_by_compatible("amd,pensando-elba-syscon");
> - if (IS_ERR(regmap))
> - return PTR_ERR(regmap);
> + node = of_parse_phandle(np, "pensando,elba-syscon-spics", 0);
1. Property name must be structured with the permitted vendor-prefix. In
your case it's "amd," not "pensando,".
2. Having 'spics' in the property name doesn't make much sense since
the property is supposed to contain a phandle reference to the whole
syscon node.
So to speak the property with name like 'amd,pensando-elba-syscon'
seems more appropriate here.
> + if (node) {
> + regmap = syscon_node_to_regmap(node);
> + if (IS_ERR(regmap))
> + return PTR_ERR(regmap);
> + }
>
> diff --git a/arch/arm64/boot/dts/amd/elba.dtsi
> b/arch/arm64/boot/dts/amd/elba.dtsi
> index 9739641261c3..ec48be4cfe48 100644
> --- a/arch/arm64/boot/dts/amd/elba.dtsi
> +++ b/arch/arm64/boot/dts/amd/elba.dtsi
> @@ -98,6 +98,7 @@
> reg = <0x0 0x2800 0x0 0x100>;
> #address-cells = <1>;
> #size-cells = <0>;
> + pensando,elba-syscon-spics = <&syscon>;
+ amd,pensando-elba-syscon = <&syscon>;
ditto
> clocks = <&ahb_clk>;
> interrupts = <GIC_SPI 9 IRQ_TYPE_LEVEL_HIGH>;
> num-cs = <2>;
>
> --- a/Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.yaml
> +++ b/Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.yaml
> @@ -37,6 +37,15 @@ allOf:
> else:
> required:
> - interrupts
> + - if:
> + properties:
> + compatible:
> + contains:
> + enum:
> + - amd,pensando-elba-spi
> + then:
+ properties:
+ amd,pensando-elba-syscon
+ $ref: /schemas/types.yaml#/definitions/phandle
+ description: AMD Pensando Elba SoC system controller
> + required:
> + - amd,pensando-elba-syscon
Please make sure the DT-bindings check passes correctly.
-Sergey
>
> properties:
> compatible:
>
> Regards,
> Brad
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