soc/tegra: pmc: Factor out DPD register bit calculation

Factor out the the code to calculate the correct DPD register and bit
number for a given pad. This logic will be needed to query the status
register.
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

@@ -922,11 +922,12 @@ tegra_io_pad_find(struct tegra_pmc *pmc, enum tegra_io_pad id)
 	return NULL;
 }
 
-static int tegra_io_pad_prepare(enum tegra_io_pad id, unsigned long *request,
-				unsigned long *status, u32 *mask)
+static int tegra_io_pad_get_dpd_register_bit(enum tegra_io_pad id,
+					     unsigned long *request,
+					     unsigned long *status,
+					     u32 *mask)
 {
 	const struct tegra_io_pad_soc *pad;
-	unsigned long rate, value;
 
 	pad = tegra_io_pad_find(pmc, id);
 	if (!pad) {
@@ -947,6 +948,19 @@ static int tegra_io_pad_prepare(enum tegra_io_pad id, unsigned long *request,
 		*request = pmc->soc->regs->dpd2_req;
 	}
 
+	return 0;
+}
+
+static int tegra_io_pad_prepare(enum tegra_io_pad id, unsigned long *request,
+				unsigned long *status, u32 *mask)
+{
+	unsigned long rate, value;
+	int err;
+
+	err = tegra_io_pad_get_dpd_register_bit(id, request, status, mask);
+	if (err)
+		return err;
+
 	if (pmc->clk) {
 		rate = clk_get_rate(pmc->clk);
 		if (!rate) {