linux-kernel - Re: [PATCH v4 1/3] dt-bindings: mmc: add cap-sdio-async-irq flag

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Date:   Mon, 14 Feb 2022 16:23:10 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Axe Yang <axe.yang@...iatek.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Chaotian Jing <chaotian.jing@...iatek.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Satya Tangirala <satyat@...gle.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Lucas Stach <dev@...xeye.de>,
        Eric Biggers <ebiggers@...gle.com>,
        Andrew Jeffery <andrew@...id.au>,
        Stephen Boyd <swboyd@...omium.org>,
        Kiwoong Kim <kwmad.kim@...sung.com>,
        Yue Hu <huyue2@...ong.com>, Tian Tao <tiantao6@...ilicon.com>,
        angelogioacchino.delregno@...labora.com, linux-mmc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v4 1/3] dt-bindings: mmc: add cap-sdio-async-irq flag

On Wed, 19 Jan 2022 at 11:32, Axe Yang <axe.yang@...iatek.com> wrote:
>
> Asynchronous interrupt is a mechanism that allow SDIO devices alarm
> interrupt when host stop providing clock to card. Add a DT flag to
> enable this feature if it is supported by SDIO card.
>
> Signed-off-by: Axe Yang <axe.yang@...iatek.com>
> ---
>  Documentation/devicetree/bindings/mmc/mmc-controller.yaml | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/mmc/mmc-controller.yaml b/Documentation/devicetree/bindings/mmc/mmc-controller.yaml
> index 513f3c8758aa..16fb06f88471 100644
> --- a/Documentation/devicetree/bindings/mmc/mmc-controller.yaml
> +++ b/Documentation/devicetree/bindings/mmc/mmc-controller.yaml
> @@ -165,6 +165,11 @@ properties:
>      description:
>        eMMC hardware reset is supported
>
> +  cap-sdio-async-irq:
> +    $ref: /schemas/types.yaml#/definitions/flag
> +    description:
> +      SDIO async interrupt is supported.

We already have a DT property for this, I believe.

"wakeup-source" is probably what you want, but we have additional
properties that are related to this too. See more below.

> +
>    cap-sdio-irq:
>      $ref: /schemas/types.yaml#/definitions/flag
>      description:

The above, "cap-sdio-irq", informs whether the SDIO IRQs can be
supported at all, by the host controller.

The property "keep-power-in-suspend" informs whether we can preserve
the power to the card during a suspend/resume cycle. This should be
needed in your case too, I think.

In other words, you may need to combine "cap-sdio-irq",
"wakeup-source" and "keep-power-in-suspend" to describe your HW.

However, what perhaps is missing, is a common MMC/SDIO binding that
let us describe an optional irq-line, which sometimes is being used
for the wakeup irq. In the sdhci-omap case, we look for an irq mapping
towards "wakeup" if specified in the "interrupt-names" property.

In some case, when the SDIO card supports an out-of-band IRQ line, the
similar should be specified in the child-node corresponding to the
SDIO card.

Kind regards
Uffe