mmc: sdhci: add get_cd() implementation

1. mmc_rescan will call get_cd to know whether the card is present
before mmc_rescan_try_freq to avoid useless trials during
card removal or start host is called when card is not present.

2. get_cd needs to be checked to resolve slow card removal issue.
Signed-off-by: Kevin Liu <kliu5@marvell.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

drivers/mmc/host/sdhci.c

@@ -1581,6 +1581,37 @@ static void sdhci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
 	sdhci_runtime_pm_put(host);
 }
 
+static int sdhci_do_get_cd(struct sdhci_host *host)
+{
+	int gpio_cd = mmc_gpio_get_cd(host->mmc);
+
+	if (host->flags & SDHCI_DEVICE_DEAD)
+		return 0;
+
+	/* If polling/nonremovable, assume that the card is always present. */
+	if ((host->quirks & SDHCI_QUIRK_BROKEN_CARD_DETECTION) ||
+	    (host->mmc->caps & MMC_CAP_NONREMOVABLE))
+		return 1;
+
+	/* Try slot gpio detect */
+	if (!IS_ERR_VALUE(gpio_cd))
+		return !!gpio_cd;
+
+	/* Host native card detect */
+	return !!(sdhci_readl(host, SDHCI_PRESENT_STATE) & SDHCI_CARD_PRESENT);
+}
+
+static int sdhci_get_cd(struct mmc_host *mmc)
+{
+	struct sdhci_host *host = mmc_priv(mmc);
+	int ret;
+
+	sdhci_runtime_pm_get(host);
+	ret = sdhci_do_get_cd(host);
+	sdhci_runtime_pm_put(host);
+	return ret;
+}
+
 static int sdhci_check_ro(struct sdhci_host *host)
 {
 	unsigned long flags;
@@ -2038,6 +2069,7 @@ static void sdhci_card_event(struct mmc_host *mmc)
 static const struct mmc_host_ops sdhci_ops = {
 	.request	= sdhci_request,
 	.set_ios	= sdhci_set_ios,
+	.get_cd		= sdhci_get_cd,
 	.get_ro		= sdhci_get_ro,
 	.hw_reset	= sdhci_hw_reset,
 	.enable_sdio_irq = sdhci_enable_sdio_irq,