[PATCH 08/10] pmdomain: samsung: try to get PMU (syscon) regmap

["André Draszik" <andre.draszik@linaro.org>]

On platforms such as Google gs101, direct mmio register access to the
PMU registers doesn't necessarily work and access must happen via a
(syscon) regmap created by the PMU driver instead.

Try to obtain this regmap using the parent node in DT in case this PD
is a child of the PMU and fall back to the traditional direct mmio
regmap otherwise.

Signed-off-by: André Draszik <andre.draszik@linaro.org>
---
 drivers/pmdomain/samsung/exynos-pm-domains.c | 58 ++++++++++++++++++----------
 1 file changed, 38 insertions(+), 20 deletions(-)

diff --git a/drivers/pmdomain/samsung/exynos-pm-domains.c b/drivers/pmdomain/samsung/exynos-pm-domains.c
index 5a87802cff394945cb0202d08f2cf6bcbbcc774d..c1b5830b2ad3e8b272dcc8ebc364be49aa7fda7c 100644
--- a/drivers/pmdomain/samsung/exynos-pm-domains.c
+++ b/drivers/pmdomain/samsung/exynos-pm-domains.c
@@ -12,6 +12,7 @@
 #include <linux/err.h>
 #include <linux/platform_device.h>
 #include <linux/slab.h>
+#include <linux/mfd/syscon.h>
 #include <linux/pm_domain.h>
 #include <linux/of.h>
 #include <linux/pm_runtime.h>
@@ -107,17 +108,9 @@ static int exynos_pd_probe(struct platform_device *pdev)
 	struct of_phandle_args child, parent;
 	struct exynos_pm_domain *pd;
 	struct resource *res;
-	void __iomem *base;
 	unsigned int val;
 	int on, ret;
 
-	struct regmap_config reg_config = {
-		.reg_bits = 32,
-		.val_bits = 32,
-		.reg_stride = 4,
-		.use_relaxed_mmio = true,
-	};
-
 	pm_domain_cfg = of_device_get_match_data(dev);
 	pd = devm_kzalloc(dev, sizeof(*pd), GFP_KERNEL);
 	if (!pd)
@@ -128,25 +121,50 @@ static int exynos_pd_probe(struct platform_device *pdev)
 		return -ENOMEM;
 
 	/*
-	 * The resource typically points into the address space of the PMU.
+	 * The resource typically points into the address space of the PMU and
+	 * we have to consider two cases:
+	 *   1) some implementations require a custom syscon regmap
+	 *   2) this driver might map the same addresses as the PMU driver
 	 * Therefore, avoid using devm_platform_get_and_ioremap_resource() and
-	 * instead use platform_get_resource() and devm_ioremap() to avoid
+	 * instead use platform_get_resource() here, and below for case 1) use
+	 * syscon_node_to_regmap() while for case 2) use devm_ioremap() to avoid
 	 * conflicts due to address space overlap.
 	 */
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	if (!res)
 		return dev_err_probe(dev, -ENXIO, "missing IO resources");
 
-	base = devm_ioremap(dev, res->start, resource_size(res));
-	if (!base)
-		return dev_err_probe(dev, -ENOMEM,
-				     "failed to ioremap PMU registers");
-
-	reg_config.max_register = resource_size(res) - reg_config.reg_stride;
-	pd->regmap = devm_regmap_init_mmio(dev, base, &reg_config);
-	if (IS_ERR(pd->regmap))
-		return dev_err_probe(dev, PTR_ERR(base),
-				     "failed to init regmap");
+	if (dev->parent &&
+	    of_device_is_compatible(dev->parent->of_node, "syscon")) {
+		pd->regmap = syscon_node_to_regmap(dev->parent->of_node);
+		if (IS_ERR(pd->regmap))
+			return dev_err_probe(dev, PTR_ERR(pd->regmap),
+					     "failed to acquire PMU regmap");
+
+		pd->configuration_reg = res->start;
+		pd->status_reg = res->start;
+	} else {
+		void __iomem *base;
+
+		const struct regmap_config reg_config = {
+			.reg_bits = 32,
+			.val_bits = 32,
+			.reg_stride = 4,
+			.use_relaxed_mmio = true,
+			.max_register = (resource_size(res)
+					 - reg_config.reg_stride),
+		};
+
+		base = devm_ioremap(dev, res->start, resource_size(res));
+		if (!base)
+			return dev_err_probe(dev, -ENOMEM,
+					     "failed to ioremap PMU registers");
+
+		pd->regmap = devm_regmap_init_mmio(dev, base, &reg_config);
+		if (IS_ERR(pd->regmap))
+			return dev_err_probe(dev, PTR_ERR(base),
+					     "failed to init regmap");
+	}
 
 	pd->pd.power_off = exynos_pd_power_off;
 	pd->pd.power_on = exynos_pd_power_on;

-- 
2.51.0.618.g983fd99d29-goog