[PATCH 2/2] drivers: mmc: Add wait_dat0 support for sdhci driver

[stcarlso@linux.microsoft.com]

From: Stephen Carlson <stcarlso@linux.microsoft.com>

Adds an implementation of the wait_dat0 MMC operation for the DM SDHCI
driver, allowing the driver to continue when the card is ready rather
than waiting for the worst case time on each MMC switch operation.

Signed-off-by: Stephen Carlson <stcarlso@linux.microsoft.com>
---
 drivers/mmc/sdhci.c | 20 ++++++++++++++++++++
 include/sdhci.h     |  2 ++
 2 files changed, 22 insertions(+)

diff --git a/drivers/mmc/sdhci.c b/drivers/mmc/sdhci.c
index eea4701d8a..bb55e00ef5 100644
--- a/drivers/mmc/sdhci.c
+++ b/drivers/mmc/sdhci.c
@@ -775,6 +775,25 @@ static int sdhci_get_cd(struct udevice *dev)
 		return value;
 }
 
+static int sdhci_wait_dat0(struct udevice *dev, int state,
+			   int timeout_us)
+{
+	int tmp;
+	struct mmc *mmc = mmc_get_mmc_dev(dev);
+	struct sdhci_host *host = mmc->priv;
+	unsigned long timeout = timer_get_us() + timeout_us;
+
+	// readx_poll_timeout is unsuitable because sdhci_readl accepts
+	// two arguments
+	do {
+		tmp = sdhci_readl(host, SDHCI_PRESENT_STATE);
+		if (!!(tmp & SDHCI_DATA_0_LVL_MASK) == !!state)
+			return 0;
+	} while (!timeout_us || !time_after(timer_get_us(), timeout));
+
+	return -ETIMEDOUT;
+}
+
 const struct dm_mmc_ops sdhci_ops = {
 	.send_cmd	= sdhci_send_command,
 	.set_ios	= sdhci_set_ios,
@@ -783,6 +802,7 @@ const struct dm_mmc_ops sdhci_ops = {
 #ifdef MMC_SUPPORTS_TUNING
 	.execute_tuning	= sdhci_execute_tuning,
 #endif
+	.wait_dat0	= sdhci_wait_dat0,
 };
 #else
 static const struct mmc_ops sdhci_ops = {
diff --git a/include/sdhci.h b/include/sdhci.h
index 0ae9471ad7..dd4eb41442 100644
--- a/include/sdhci.h
+++ b/include/sdhci.h
@@ -65,6 +65,8 @@
 #define  SDHCI_CARD_STATE_STABLE	BIT(17)
 #define  SDHCI_CARD_DETECT_PIN_LEVEL	BIT(18)
 #define  SDHCI_WRITE_PROTECT	BIT(19)
+#define  SDHCI_DATA_LVL_MASK	0x00F00000
+#define   SDHCI_DATA_0_LVL_MASK BIT(20)
 
 #define SDHCI_HOST_CONTROL	0x28
 #define  SDHCI_CTRL_LED		BIT(0)
-- 
2.17.1