mmc: sdhci-pci: Fix voltage switch for some Intel host controllers

Some Intel host controllers (e.g. CNP) use an ACPI device-specific method
to ensure correct voltage switching. Fix voltage switch for those, by
adding a call to the DSM.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

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

@@ -392,6 +392,7 @@ static const struct sdhci_pci_fixes sdhci_intel_pch_sdio = {
 
 enum {
 	INTEL_DSM_FNS		=  0,
+	INTEL_DSM_V18_SWITCH	=  3,
 	INTEL_DSM_DRV_STRENGTH	=  9,
 	INTEL_DSM_D3_RETUNE	= 10,
 };
@@ -557,6 +558,19 @@ static void intel_hs400_enhanced_strobe(struct mmc_host *mmc,
 	sdhci_writel(host, val, INTEL_HS400_ES_REG);
 }
 
+static void sdhci_intel_voltage_switch(struct sdhci_host *host)
+{
+	struct sdhci_pci_slot *slot = sdhci_priv(host);
+	struct intel_host *intel_host = sdhci_pci_priv(slot);
+	struct device *dev = &slot->chip->pdev->dev;
+	u32 result = 0;
+	int err;
+
+	err = intel_dsm(intel_host, dev, INTEL_DSM_V18_SWITCH, &result);
+	pr_debug("%s: %s DSM error %d result %u\n",
+		 mmc_hostname(host->mmc), __func__, err, result);
+}
+
 static const struct sdhci_ops sdhci_intel_byt_ops = {
 	.set_clock		= sdhci_set_clock,
 	.set_power		= sdhci_intel_set_power,
@@ -565,6 +579,7 @@ static const struct sdhci_ops sdhci_intel_byt_ops = {
 	.reset			= sdhci_reset,
 	.set_uhs_signaling	= sdhci_set_uhs_signaling,
 	.hw_reset		= sdhci_pci_hw_reset,
+	.voltage_switch		= sdhci_intel_voltage_switch,
 };
 
 static void byt_read_dsm(struct sdhci_pci_slot *slot)