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Subject[PATCH] mmc: core: Wait for Vdd to settle on card power off
Date
The SD spec version 6.0 section 6.4.1.5 requires that Vdd must be
lowered to less than 0.5V for a minimum of 1 ms when powering off a
card. Increase our wait to 10 ms so that voltage has time to drain down
to 0.5V and cards can power off correctly.

Signed-off-by: Kyle Roeschley <kyle.roeschley@ni.com>
---
drivers/mmc/core/core.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 66c9cf49ad2f..38630246de26 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -1679,18 +1679,16 @@ void mmc_power_off(struct mmc_host *host)
mmc_set_initial_state(host);

/*
- * Some configurations, such as the 802.11 SDIO card in the OLPC
- * XO-1.5, require a short delay after poweroff before the card
- * can be successfully turned on again.
+ * The SD spec requires at least 1 ms with Vdd at less than 0.5 V
+ * before a card can be re-powered, but we need to wait longer so that
+ * the voltage has time to drain.
*/
- mmc_delay(1);
+ mmc_delay(10);
}

void mmc_power_cycle(struct mmc_host *host, u32 ocr)
{
mmc_power_off(host);
- /* Wait at least 1 ms according to SD spec */
- mmc_delay(1);
mmc_power_up(host, ocr);
}

--
2.14.1
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