sdhci: Advertise 2.0v supply on SDIO host controller

On Intel Edison the Broadcom Wi-Fi card, which is connected to SDIO,
requires 2.0v, while the host, according to Intel Merrifield TRM,
supports 1.8v supply only.

The card announces itself as

  mmc2: new ultra high speed DDR50 SDIO card at address 0001

Introduce a custom OCR mask for SDIO host controller on Intel Merrifield
and add a special case to sdhci_set_power_noreg() to override 2.0v supply
by enforcing 1.8v power choice.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/sdhci-pci-core.c

@@ -930,6 +930,8 @@ static int intel_mrfld_mmc_probe_slot(struct sdhci_pci_slot *slot)
 		slot->host->quirks2 |= SDHCI_QUIRK2_NO_1_8_V;
 		break;
 	case INTEL_MRFLD_SDIO:
+		/* Advertise 2.0v for compatibility with the SDIO card's OCR */
+		slot->host->ocr_mask = MMC_VDD_20_21 | MMC_VDD_165_195;
 		slot->host->mmc->caps |= MMC_CAP_NONREMOVABLE |
 					 MMC_CAP_POWER_OFF_CARD;
 		break;

drivers/mmc/host/sdhci.c

@@ -1434,6 +1434,13 @@ void sdhci_set_power_noreg(struct sdhci_host *host, unsigned char mode,
 	if (mode != MMC_POWER_OFF) {
 		switch (1 << vdd) {
 		case MMC_VDD_165_195:
+		/*
+		 * Without a regulator, SDHCI does not support 2.0v
+		 * so we only get here if the driver deliberately
+		 * added the 2.0v range to ocr_avail. Map it to 1.8v
+		 * for the purpose of turning on the power.
+		 */
+		case MMC_VDD_20_21:
 			pwr = SDHCI_POWER_180;
 			break;
 		case MMC_VDD_29_30: