On Nov 25, 2012, at 6:01 PM, Daniel Drake <dsd@xxxxxxxxxx> wrote:
> The OLPC XO-1.75 laptop includes a SDHCI controller which is 1.8v
> capable, and it truthfully reports so in its capabilities. This
> alternate voltage is used for driving new "UHS-I" SD cards at their
> full speed.
>
> However, what the controller doesn't know is that the motherboard
> physically doesn't have a 1.8v supply available.
>
> Add a quirk so that systems such as this one can override disable
> 1.8v support, adding support for UHS-I cards (by running them at
> 3.3v).
>
> This avoids a problem where the system would first try to run the
> card at 1.8v, fail, and then not be able to fully reset the card
> to retry at the normal 3.3v voltage.
>
> This is more appropriate than using the MISSING_CAPS quirk, which
> is intended for cases where the SDHCI controller is actually lying
> about its capabilities, and would force us to somehow override both
> caps words from another source.
>
> Signed-off-by: Daniel Drake <dsd@xxxxxxxxxx>
> ---
> drivers/mmc/host/sdhci.c | 4 ++++
> include/linux/mmc/sdhci.h | 2 ++
> 2 files changed, 6 insertions(+)
>
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index c7851c0..7273523 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -2865,6 +2865,10 @@ int sdhci_add_host(struct sdhci_host *host)
> caps[1] &= ~(SDHCI_SUPPORT_SDR104 | SDHCI_SUPPORT_SDR50 |
> SDHCI_SUPPORT_DDR50);
>
> + if (host->quirks2 & SDHCI_QUIRK2_NO_1_8_V)
> + caps[1] &= ~(SDHCI_SUPPORT_SDR104 | SDHCI_SUPPORT_SDR50 |
> + SDHCI_SUPPORT_DDR50);
> +
> /* Any UHS-I mode in caps implies SDR12 and SDR25 support. */
> if (caps[1] & (SDHCI_SUPPORT_SDR104 | SDHCI_SUPPORT_SDR50 |
> SDHCI_SUPPORT_DDR50))
> diff --git a/include/linux/mmc/sdhci.h b/include/linux/mmc/sdhci.h
> index 1edcb4d..1a42747 100644
> --- a/include/linux/mmc/sdhci.h
> +++ b/include/linux/mmc/sdhci.h
> @@ -92,6 +92,8 @@ struct sdhci_host {
>
> #define SDHCI_QUIRK2_HOST_OFF_CARD_ON (1<<0)
> #define SDHCI_QUIRK2_HOST_NO_CMD23 (1<<1)
> +/* The system physically doesn't support 1.8v, even if the host does */
> +#define SDHCI_QUIRK2_NO_1_8_V (1<<2)
>
> int irq; /* Device IRQ */
> void __iomem *ioaddr; /* Mapped address */
> --
> 1.7.11.7
>
Reviewed-by: Philip Rakity <prakity@xxxxxxxxxx>
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