From 569fd6029e77f6b3ea0dc23dfc0ef32239cf55c9 Mon Sep 17 00:00:00 2001
From: Thierry Reding <treding@nvidia.com>
Date: Thu, 17 Jul 2014 15:29:46 +0200
Subject: [PATCH] PCI: tegra: Preserve DT backwards-compatibility

Parse the set of power supplies in the deprecated version of the device
tree binding to remain backwards-compatible with old device trees.

Signed-off-by: Thierry Reding <treding@nvidia.com>
---
 drivers/pci/host/pci-tegra.c | 78 ++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 76 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/host/pci-tegra.c b/drivers/pci/host/pci-tegra.c
index 7df5aaf58921..d697587dbb7c 100644
--- a/drivers/pci/host/pci-tegra.c
+++ b/drivers/pci/host/pci-tegra.c
@@ -1359,6 +1359,66 @@ static int tegra_pcie_get_xbar_config(struct tegra_pcie *pcie, u32 lanes,
 }
 
 /*
+ * Check whether a given set of supplies is available in a device tree node.
+ * This is used to check whether the new or the legacy device tree bindings
+ * should be used.
+ */
+static bool of_regulator_bulk_available(struct device_node *np,
+					struct regulator_bulk_data *supplies,
+					unsigned int num_supplies)
+{
+	char property[32];
+	unsigned int i;
+
+	for (i = 0; i < num_supplies; i++) {
+		snprintf(property, 32, "%s-supply", supplies[i].supply);
+
+		if (of_find_property(np, property, NULL) == NULL)
+			return false;
+	}
+
+	return true;
+}
+
+/*
+ * Old versions of the device tree binding for this device used a set of power
+ * supplies that didn't match the hardware inputs. This happened to work for a
+ * number of cases but is not future proof. However to preserve backwards-
+ * compatibility with old device trees, this function will try to use the old
+ * set of supplies.
+ */
+static int tegra_pcie_get_legacy_regulators(struct tegra_pcie *pcie)
+{
+	struct device_node *np = pcie->dev->of_node;
+
+	if (of_device_is_compatible(np, "nvidia,tegra30-pcie"))
+		pcie->num_supplies = 3;
+	else if (of_device_is_compatible(np, "nvidia,tegra20-pcie"))
+		pcie->num_supplies = 2;
+
+	if (pcie->num_supplies == 0) {
+		dev_err(pcie->dev, "device %s not supported in legacy mode\n",
+			np->full_name);
+		return -ENODEV;
+	}
+
+	pcie->supplies = devm_kcalloc(pcie->dev, pcie->num_supplies,
+				      sizeof(*pcie->supplies),
+				      GFP_KERNEL);
+	if (!pcie->supplies)
+		return -ENOMEM;
+
+	pcie->supplies[0].supply = "pex-clk";
+	pcie->supplies[1].supply = "vdd";
+
+	if (pcie->num_supplies > 2)
+		pcie->supplies[2].supply = "avdd";
+
+	return devm_regulator_bulk_get(pcie->dev, pcie->num_supplies,
+				       pcie->supplies);
+}
+
+/*
  * Obtains the list of regulators required for a particular generation of the
  * IP block.
  *
@@ -1422,8 +1482,22 @@ static int tegra_pcie_get_regulators(struct tegra_pcie *pcie, u32 lane_mask)
 		pcie->supplies[4].supply = "vddio-pex-clk";
 	}
 
-	return devm_regulator_bulk_get(pcie->dev, pcie->num_supplies,
-				       pcie->supplies);
+	if (of_regulator_bulk_available(pcie->dev->of_node, pcie->supplies,
+					pcie->num_supplies))
+		return devm_regulator_bulk_get(pcie->dev, pcie->num_supplies,
+					       pcie->supplies);
+
+	/*
+	 * If not all regulators are available for this new scheme, assume
+	 * that the device tree complies with an older version of the device
+	 * tree binding.
+	 */
+	dev_info(pcie->dev, "using legacy DT binding for power supplies\n");
+
+	devm_kfree(pcie->dev, pcie->supplies);
+	pcie->num_supplies = 0;
+
+	return tegra_pcie_get_legacy_regulators(pcie);
 }
 
 static int tegra_pcie_parse_dt(struct tegra_pcie *pcie)
-- 
2.0.1