From: Ohad Ben-Cohen <ohad@xxxxxxxxxx>
To save power, the pull-up resistor on CD/DAT[3] (pin 1)
of the card can be disconnected. This is desired, e.g.,
with embedded SDIO devices which do not rely on this pin
for card detection.
Signed-off-by: Ohad Ben-Cohen <ohad@xxxxxxxxxx>
---
drivers/mmc/core/sdio.c | 32 ++++++++++++++++++++++++++++++++
include/linux/mmc/card.h | 3 ++-
2 files changed, 34 insertions(+), 1 deletions(-)
diff --git a/drivers/mmc/core/sdio.c b/drivers/mmc/core/sdio.c
index fb99ccf..4c4c9a9 100644
--- a/drivers/mmc/core/sdio.c
+++ b/drivers/mmc/core/sdio.c
@@ -165,6 +165,31 @@ static int sdio_enable_wide(struct mmc_card *card)
}
/*
+ * Disconnect the pull-up resistor on CD/DAT[3] if requested by the card.
+ * If card detection is not needed, this can save some power.
+ */
+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;
+
+ ret = mmc_io_rw_direct(card, 1, 0, SDIO_CCCR_IF, ctrl, NULL);
+ if (ret)
+ return ret;
+
+ return 0;
+}
+
+/*
* Test if the card supports high-speed mode and, if so, switch to it.
*/
static int sdio_enable_hs(struct mmc_card *card)
@@ -392,6 +417,13 @@ int mmc_attach_sdio(struct mmc_host *host, u32 ocr)
goto remove;
/*
+ * Disconnect card detection pull-up resistor (if requested by card).
+ */
+ err = sdio_disable_cd(card);
+ if (err)
+ goto remove;
+
+ /*
* Initialize (but don't add) all present functions.
*/
for (i = 0;i < funcs;i++) {
diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
index 403aa50..82a8488 100644
--- a/include/linux/mmc/card.h
+++ b/include/linux/mmc/card.h
@@ -62,7 +62,8 @@ struct sdio_cccr {
low_speed:1,
wide_bus:1,
high_power:1,
- high_speed:1;
+ high_speed:1,
+ disable_cd:1;
};
struct sdio_cis {
--
1.5.4.3
--
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