soc/tegra: pmc: Implement tegra_io_pad_is_powered()

Implement a function to query whether a pad is in deep power down mode.
This is needed by the pinctrl callbacks.

Signed-off-by: Aapo Vienamo <avienamo@nvidia.com>
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/soc/tegra/pmc.c

@@ -1075,6 +1075,21 @@ unlock:
 }
 EXPORT_SYMBOL(tegra_io_pad_power_disable);
 
+static int tegra_io_pad_is_powered(enum tegra_io_pad id)
+{
+	unsigned long request, status;
+	u32 mask, value;
+	int err;
+
+	err = tegra_io_pad_get_dpd_register_bit(id, &request, &status, &mask);
+	if (err)
+		return err;
+
+	value = tegra_pmc_readl(status);
+
+	return !(value & mask);
+}
+
 int tegra_io_pad_set_voltage(enum tegra_io_pad id,
 			     enum tegra_io_pad_voltage voltage)
 {