mmc: sdhci-of-at91: add DT property to enable calibration on full reset

Add a property to keep the analog calibration cell powered.
This feature is specific to the Microchip SDHCI IP and outside
of the standard SDHCI register map.

By always keeping it on, after a full reset sequence, we make sure
that this feature is activated and not disabled.

We expose a hardware property to the DT as this feature can be used
to adapt SDHCI behavior vs. how the SDCAL SoC pin is connected
on the board.

Note that managing properly this property would reduce
power consumption on some SAMA5D2 SiP revisions.
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Acked-by: Ludovic Desroches <ludovic.desroches@microchip.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/sdhci-of-at91.c

@@ -27,6 +27,9 @@
 #define SDMMC_CACR	0x230
 #define		SDMMC_CACR_CAPWREN	BIT(0)
 #define		SDMMC_CACR_KEY		(0x46 << 8)
+#define SDMMC_CALCR	0x240
+#define		SDMMC_CALCR_EN		BIT(0)
+#define		SDMMC_CALCR_ALWYSON	BIT(4)
 
 #define SDHCI_AT91_PRESET_COMMON_CONF	0x400 /* drv type B, programmable clock mode */
 
@@ -35,6 +38,7 @@ struct sdhci_at91_priv {
 	struct clk *gck;
 	struct clk *mainck;
 	bool restore_needed;
+	bool cal_always_on;
 };
 
 static void sdhci_at91_set_force_card_detect(struct sdhci_host *host)
@@ -116,10 +120,17 @@ static void sdhci_at91_set_uhs_signaling(struct sdhci_host *host,
 
 static void sdhci_at91_reset(struct sdhci_host *host, u8 mask)
 {
+	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
+	struct sdhci_at91_priv *priv = sdhci_pltfm_priv(pltfm_host);
+
 	sdhci_reset(host, mask);
 
 	if (host->mmc->caps & MMC_CAP_NONREMOVABLE)
 		sdhci_at91_set_force_card_detect(host);
+
+	if (priv->cal_always_on && (mask & SDHCI_RESET_ALL))
+		sdhci_writel(host, SDMMC_CALCR_ALWYSON | SDMMC_CALCR_EN,
+			     SDMMC_CALCR);
 }
 
 static const struct sdhci_ops sdhci_at91_sama5d2_ops = {
@@ -345,6 +356,14 @@ static int sdhci_at91_probe(struct platform_device *pdev)
 
 	priv->restore_needed = false;
 
+	/*
+	 * if SDCAL pin is wrongly connected, we must enable
+	 * the analog calibration cell permanently.
+	 */
+	priv->cal_always_on =
+		device_property_read_bool(&pdev->dev,
+					  "microchip,sdcal-inverted");
+
 	ret = mmc_of_parse(host->mmc);
 	if (ret)
 		goto clocks_disable_unprepare;