linux-kernel - Re: [PATCH RESEND v3 1/3] dt-bindings: mmc: sdhci-am654: Add ti,suppress-v1p8-ena

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Message-ID: <20250425-agile-imported-inchworm-6ae257@kuoka>
Date: Fri, 25 Apr 2025 09:48:19 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Judith Mendez <jm@...com>
Cc: Ulf Hansson <ulf.hansson@...aro.org>, Nishanth Menon <nm@...com>, 
	Adrian Hunter <adrian.hunter@...el.com>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Vignesh Raghavendra <vigneshr@...com>, Tero Kristo <kristo@...nel.org>, 
	Josua Mayer <josua@...id-run.com>, linux-mmc@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	Francesco Dolcini <francesco@...cini.it>, Hiago De Franco <hiagofranco@...il.com>, 
	Moteen Shah <m-shah@...com>, stable@...r.kernel.org
Subject: Re: [PATCH RESEND v3 1/3] dt-bindings: mmc: sdhci-am654: Add
 ti,suppress-v1p8-ena

On Tue, Apr 22, 2025 at 05:05:10PM GMT, Judith Mendez wrote:
> Some Microcenter/Patriot SD cards and Kingston eMMC are failing init
> across Sitara K3 boards. Init failure is due to the sequence when
> V1P8_SIGNAL_ENA is set. The V1P8_SIGNAL_ENA has a timing component tied
> to it where if set, switch to full-cycle timing happens. The failing
> cards do not like change to full-cycle timing before changing bus
> width, so add flag to sdhci-am654 binding to suppress V1P8_SIGNAL_ENA
> before changing bus width. The switch to full-cycle timing should happen
> with HIGH_SPEED_ENA after change of bus width.
> 
> Signed-off-by: Judith Mendez <jm@...com>
> ---
>  Documentation/devicetree/bindings/mmc/sdhci-am654.yaml | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/mmc/sdhci-am654.yaml b/Documentation/devicetree/bindings/mmc/sdhci-am654.yaml
> index 676a74695389..0f92bbf8e13b 100644
> --- a/Documentation/devicetree/bindings/mmc/sdhci-am654.yaml
> +++ b/Documentation/devicetree/bindings/mmc/sdhci-am654.yaml
> @@ -201,6 +201,11 @@ properties:
>        and the controller is required to be forced into Test mode
>        to set the TESTCD bit.
>  
> +  ti,suppress-v1p8-ena:

Do not tell what the drivers should do, but tell what is the issue with
the hardware, e.g. some cards do not like full-cycle.... and this will
also hint you that it should be most likely generic, not specific to
this device.

> +    $ref: /schemas/types.yaml#/definitions/flag
> +    description:

Best regards,
Krzysztof