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mmc: sdhci: add quirk for lack of 1.8v support

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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 <[email protected]>
Reviewed-by: Philip Rakity <[email protected]>
Signed-off-by: Chris Ball <[email protected]>
This commit is contained in:
Daniel Drake 2012-11-25 13:01:19 -05:00 • committed by Chris Ball
commit 6a66180a25
2 changed files with 6 additions and 0 deletions
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4
drivers/mmc/host/sdhci.c
View file

@ -2867,6 +2867,10 @@ int sdhci_add_host(struct sdhci_host *host)
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))