linux-kernel - Re: [PATCH v3 05/11] mmc: sdhci: Disable HS200 mode if controller can't support 1.8v

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Message-ID: <fc379441-ed8e-47b4-f34b-d4137d158ec6@intel.com>
Date:   Thu, 15 Mar 2018 12:58:37 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Kishon Vijay Abraham I <kishon@...com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Tony Lindgren <tony@...mide.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        linux-mmc@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 05/11] mmc: sdhci: Disable HS200 mode if controller
 can't support 1.8v

On 07/03/18 15:20, Kishon Vijay Abraham I wrote:
> Though MMC controller can indicate HS200 mode capability (by
> using "mmc-hs200-1_8v" dt property), if the IO lines in the board
> is connected to 3.3v supply, HS200 mode cannot be supported.
> Such boards have "no-1-8-v" property in their dts file. Disable HS200
> mode for boards which have "no-1-8-v" set.
> 
> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
> ---
>  drivers/mmc/host/sdhci.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 2ededa7f43df..aa8b5ca0d1b0 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -3672,6 +3672,7 @@ int sdhci_setup_host(struct sdhci_host *host)
>  	if (host->quirks2 & SDHCI_QUIRK2_NO_1_8_V) {
>  		host->caps1 &= ~(SDHCI_SUPPORT_SDR104 | SDHCI_SUPPORT_SDR50 |
>  				 SDHCI_SUPPORT_DDR50);
> +		mmc->caps2 &= ~MMC_CAP2_HS200;

Pedantically, shouldn't that be:

	~(MMC_CAP2_HS200_1_8V_SDR | MMC_CAP2_HS400_1_8V)

We have MMC_CAP2_HSX00_1_2V so maybe we should add:

	#define MMC_CAP2_HSX00_1_8V	(MMC_CAP2_HS200_1_8V_SDR | MMC_CAP2_HS400_1_8V)

And then

		mmc->caps2 &= ~MMC_CAP2_HSX00_1_8V;

>  	}
>  
>  	/* Any UHS-I mode in caps implies SDR12 and SDR25 support. */
>