Re: [PATCH v2 3/3] mmc: core: add support for disabling HS400 mode via DT

From: Ulf Hansson <ulf.hansson@linaro.org>
To: Lucas Stach <l.stach@pengutronix.de>,
	Chris Ruehl <chris.ruehl@gtsys.com.hk>
Cc: Adrian Hunter <adrian.hunter@intel.com>,
	Haibo Chen <haibo.chen@nxp.com>,
	 Rob Herring <robh+dt@kernel.org>,
	NXP Linux Team <linux-imx@nxp.com>,
	 Sascha Hauer <kernel@pengutronix.de>,
	linux-mmc <linux-mmc@vger.kernel.org>,
	 DTML <devicetree@vger.kernel.org>,
	 Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v2 3/3] mmc: core: add support for disabling HS400 mode via DT
Date: Tue, 11 May 2021 13:14:44 +0200	[thread overview]
Message-ID: <CAPDyKFrAe-+CENhXkY2fGNw04g-zn+ebcAXSVGa9Td5pJcsujA@mail.gmail.com> (raw)
In-Reply-To: <20210510190400.105162-3-l.stach@pengutronix.de>

+ Chris Ruehl

On Mon, 10 May 2021 at 21:04, Lucas Stach <l.stach@pengutronix.de> wrote:
>
> From: Lucas Stach <dev@lynxeye.de>
>
> On some boards the data strobe line isn't wired up, rendering HS400
> support broken, even if both the controller and the eMMC claim to
> support it. Allow to disable HS400 mode via DT.

Before I review the series, I just wanted to highlight that quite
recently we got a related series posted from Chris [1]. I made some
comments, but he hasn't replied yet.

In any case, if I understood it correctly, it looks like some
controllers may support HS400 ES, but not HS200. Could that be the
case here as well? Or is this a different problem?

Kind regards
Uffe

[1]
https://patchwork.kernel.org/project/linux-mmc/patch/20201208061839.21163-7-chris.ruehl@gtsys.com.hk/

>
> Signed-off-by: Lucas Stach <dev@lynxeye.de>
> ---
> v2:
> - move to core
> - actually disable all HS400 modes
> ---
>  drivers/mmc/core/host.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
> index 9b89a91b6b47..0e066c5f5243 100644
> --- a/drivers/mmc/core/host.c
> +++ b/drivers/mmc/core/host.c
> @@ -351,6 +351,9 @@ int mmc_of_parse(struct mmc_host *host)
>                 host->caps2 |= MMC_CAP2_NO_SD;
>         if (device_property_read_bool(dev, "no-mmc"))
>                 host->caps2 |= MMC_CAP2_NO_MMC;
> +       if (device_property_read_bool(dev, "no-mmc-hs400"))
> +               host->caps2 &= ~(MMC_CAP2_HS400_1_8V | MMC_CAP2_HS400_1_2V |
> +                                MMC_CAP2_HS400_ES);
>
>         /* Must be after "non-removable" check */
>         if (device_property_read_u32(dev, "fixed-emmc-driver-type", &drv_type) == 0) {
> --
> 2.31.1
>

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