sdio: add CD disable support

Add support to disconnect the pull-up resistor on CD/DAT[3] (pin 1)
of the card. This may be desired on certain setups of boards,
controllers and embedded sdio devices which do not need the card's
pull-up. As a result, card detection is disabled and power is saved.

[akpm@linux-foundation.org: simplify sdio_disable_cd() a bit]
Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
Acked-by: Matt Fleming <matt@console-pimps.org>
Cc: Ian Molton <ian@mnementh.co.uk>
Cc: "Roberto A. Foglietta" <roberto.foglietta@gmail.com>
Cc: Philip Langdale <philipl@overt.org>
Cc: Pierre Ossman <pierre@ossman.eu>
Cc: David Vrabel <david.vrabel@csr.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 30 insertions, 0 deletions

diff --git a/drivers/mmc/core/sdio.c b/drivers/mmc/core/sdio.c
index 6f221dc029ad..2d24a123f0b0 100644
--- a/drivers/mmc/core/sdio.c
+++ b/drivers/mmc/core/sdio.c
@@ -165,6 +165,29 @@ static int sdio_enable_wide(struct mmc_card *card)
 }
 
 /*
+ * If desired, disconnect the pull-up resistor on CD/DAT[3] (pin 1)
+ * of the card. This may be required on certain setups of boards,
+ * controllers and embedded sdio device which do not need the card's
+ * pull-up. As a result, card detection is disabled and power is saved.
+ */
+static int sdio_disable_cd(struct mmc_card *card)
+{
+        int ret;
+        u8 ctrl;
+
+        if (!card->cccr.disable_cd)
+                return 0;
+
+        ret = mmc_io_rw_direct(card, 0, 0, SDIO_CCCR_IF, 0, &ctrl);
+        if (ret)
+                return ret;
+
+        ctrl |= SDIO_BUS_CD_DISABLE;
+
+        return mmc_io_rw_direct(card, 1, 0, SDIO_CCCR_IF, ctrl, NULL);
+}
+
+/*
  * Test if the card supports high-speed mode and, if so, switch to it.
  */
 static int sdio_enable_hs(struct mmc_card *card)
@@ -385,6 +408,13 @@ int mmc_attach_sdio(struct mmc_host *host, u32 ocr)
                 goto remove;
 
         /*
+         * If needed, disconnect card detection pull-up resistor.
+         */
+        err = sdio_disable_cd(card);
+        if (err)
+                goto remove;
+
+        /*
          * Initialize (but don't add) all present functions.
          */
         for (i = 0;i < funcs;i++) {