linux-kernel - Re: [PATCH v2 1/2] mmc: sdhci_am654: Add sdhci_am654_start_signal_voltage

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Message-ID: <aAFUxuhn_5RlbjdQ@gaggiata.pivistrello.it>
Date: Thu, 17 Apr 2025 21:21:42 +0200
From: Francesco Dolcini <francesco@...cini.it>
To: Judith Mendez <jm@...com>
Cc: Ulf Hansson <ulf.hansson@...aro.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, linux-mmc@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	Josua Mayer <josua@...id-run.com>, Moteen Shah <m-shah@...com>,
	Francesco Dolcini <francesco@...cini.it>,
	Hiago De Franco <hiagofranco@...il.com>
Subject: Re: [PATCH v2 1/2] mmc: sdhci_am654: Add
 sdhci_am654_start_signal_voltage_switch

Hello Judith,

On Thu, Apr 17, 2025 at 01:26:51PM -0500, Judith Mendez wrote:
> The sdhci_start_signal_voltage_switch function sets
> V1P8_SIGNAL_ENA by default after switching to 1v8 signaling.
> V1P8_SIGNAL_ENA has a timing component where it determines
> whether to launch cmd/data on neg edge (half cycle timing)
> or pos edge (full cycle timing) of clock. V1P8_SIGNAL_ENA also
> has a voltage switch component where if there exists an internal
> LDO, for SD this bit is used to switch from 3.3V to 1.8V IO
> signal voltage.
> 
> The sequence is to switch to 1.8 IO voltage, set V1P8_SIGNAL_ENA,
> change bus width, then update HIGH_SPEED_ENA & UHS_MODE_SELECT.
> During bus width change is when eMMC failures are seen with
> Kingston eMMC and various types SD cards across Sitara K3 SoCs.
> 
> So, add a quirk to suppress V1P8_SIGNAL_ENA and do not enable by
> default for eMMC since it is anyways optional for this interface
> and parse DT property: ti,fails-without-test-cd to apply the quirk
> for SD cards.
> 
> Signed-off-by: Judith Mendez <jm@...com>
> Suggested-by: Hiago De Franco <hiago.franco@...adex.com>

Fixes: ac5a41b472b4 ("Revert "mmc: sdhci_am654: Add sdhci_am654_start_signal_voltage_switch"")
Fixes: 941a7abd4666 ("mmc: sdhci_am654: Add sdhci_am654_start_signal_voltage_switch")
Cc:stable@...r.kernel.org