linux-kernel - Re: [PATCH v4 05/12] mmc: sdhci: Disable HS200/HS400 mode if controller can't support 1.8v

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Date:   Thu, 26 Apr 2018 11:55:20 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Kishon Vijay Abraham I <kishon@...com>,
        Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>, linux-mmc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-omap@...r.kernel.org, Tony Lindgren <tony@...mide.com>
Subject: Re: [PATCH v4 05/12] mmc: sdhci: Disable HS200/HS400 mode if
 controller can't support 1.8v

On 25/04/18 15:09, Kishon Vijay Abraham I wrote:
> Though MMC controller can indicate HS200/HS400 mode capability (by
> using "mmc-hs200-1_8v"/"mmc-hs400-1_8v" dt property), if the IO lines
> in the board is connected to 3.3v supply, HS200/HS400 mode cannot be
> supported. Such boards have "no-1-8-v" property in their dts file.
> Disable HS200/HS400 mode for boards which have "no-1-8-v" set.
> 
> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
> Acked-by: Tony Lindgren <tony@...mide.com>
> ---
>  drivers/mmc/host/sdhci.c | 1 +
>  include/linux/mmc/host.h | 1 +
>  2 files changed, 2 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 2ededa7f43df..b5f047b5f3ae 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_HSX00_1_8V;

Seems weird for sdhci to clear flags it never set.  Also couldn't we
reasonably expect dt properties to be consistent?  Is this really about
setting SDHCI_QUIRK2_NO_1_8_V in your driver and expecting it to override
other dt properties?  Although that still begs the question why anyone would
set dt properties that the hardware doesn't support?  I guess you should
also clear MMC_CAP2_HS400_ES.

>  	}
>  
>  	/* Any UHS-I mode in caps implies SDR12 and SDR25 support. */
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index 7c6eaf63f5ce..58832451767b 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -345,6 +345,7 @@ struct mmc_host {
>  #define MMC_CAP2_HS400_1_2V	(1 << 16)	/* Can support HS400 1.2V */
>  #define MMC_CAP2_HS400		(MMC_CAP2_HS400_1_8V | \
>  				 MMC_CAP2_HS400_1_2V)
> +#define MMC_CAP2_HSX00_1_8V	(MMC_CAP2_HS200_1_8V_SDR | MMC_CAP2_HS400_1_8V)
>  #define MMC_CAP2_HSX00_1_2V	(MMC_CAP2_HS200_1_2V_SDR | MMC_CAP2_HS400_1_2V)
>  #define MMC_CAP2_SDIO_IRQ_NOTHREAD (1 << 17)
>  #define MMC_CAP2_NO_WRITE_PROTECT (1 << 18)	/* No physical write protect pin, assume that card is always read-write */
>