[PATCH 7/9] drm/simplekms: Acquire regulators from DT device node

[Thomas Zimmermann]

Make sure required hardware regulators are enabled while the firmware
framebuffer is in use.

The basic code has been taken from the simplefb driver and adapted
to DRM. Regulators are released automatically via devres helpers.

Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
---
 drivers/gpu/drm/tiny/simplekms.c | 128 +++++++++++++++++++++++++++++++
 1 file changed, 128 insertions(+)

diff --git a/drivers/gpu/drm/tiny/simplekms.c b/drivers/gpu/drm/tiny/simplekms.c
index aca186decb48..ae5d3cbadbe8 100644
--- a/drivers/gpu/drm/tiny/simplekms.c
+++ b/drivers/gpu/drm/tiny/simplekms.c
@@ -4,6 +4,7 @@
 #include <linux/of_clk.h>
 #include <linux/platform_data/simplefb.h>
 #include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
 
 #include <drm/drm_atomic_state_helper.h>
 #include <drm/drm_connector.h>
@@ -198,6 +199,11 @@ struct simplekms_device {
 	unsigned int clk_count;
 	struct clk **clks;
 #endif
+	/* regulators */
+#if defined CONFIG_OF && defined CONFIG_REGULATOR
+	unsigned int regulator_count;
+	struct regulator **regulators;
+#endif
 
 	/* simplefb settings */
 	struct drm_display_mode mode;
@@ -315,6 +321,125 @@ static int simplekms_device_init_clocks(struct simplekms_device *sdev)
 }
 #endif
 
+#if defined CONFIG_OF && defined CONFIG_REGULATOR
+
+#define SUPPLY_SUFFIX "-supply"
+
+/*
+ * Regulator handling code.
+ *
+ * Here we handle the num-supplies and vin*-supply properties of our
+ * "simple-framebuffer" dt node. This is necessary so that we can make sure
+ * that any regulators needed by the display hardware that the bootloader
+ * set up for us (and for which it provided a simplefb dt node), stay up,
+ * for the life of the simplefb driver.
+ *
+ * When the driver unloads, we cleanly disable, and then release the
+ * regulators.
+ *
+ * We only complain about errors here, no action is taken as the most likely
+ * error can only happen due to a mismatch between the bootloader which set
+ * up simplefb, and the regulator definitions in the device tree. Chances are
+ * that there are no adverse effects, and if there are, a clean teardown of
+ * the fb probe will not help us much either. So just complain and carry on,
+ * and hope that the user actually gets a working fb at the end of things.
+ */
+
+static void simplekms_device_release_regulators(void *res)
+{
+	struct simplekms_device *sdev = simplekms_device_of_dev(res);
+	unsigned int i;
+
+	for (i = 0; i < sdev->regulator_count; ++i) {
+		if (sdev->regulators[i]) {
+			regulator_disable(sdev->regulators[i]);
+			regulator_put(sdev->regulators[i]);
+		}
+	}
+}
+
+static int simplekms_device_init_regulators(struct simplekms_device *sdev)
+{
+	struct drm_device *dev = &sdev->dev;
+	struct platform_device *pdev = sdev->pdev;
+	struct device_node *of_node = pdev->dev.of_node;
+	struct property *prop;
+	struct regulator *regulator;
+	const char *p;
+	unsigned int count = 0, i = 0;
+	int ret;
+
+	if (dev_get_platdata(&pdev->dev) || !of_node)
+		return 0;
+
+	/* Count the number of regulator supplies */
+	for_each_property_of_node(of_node, prop) {
+		p = strstr(prop->name, SUPPLY_SUFFIX);
+		if (p && p != prop->name)
+			++count;
+	}
+
+	if (!count)
+		return 0;
+
+	sdev->regulators = drmm_kzalloc(dev,
+					count * sizeof(sdev->regulators[0]),
+					GFP_KERNEL);
+	if (!sdev->regulators)
+		return -ENOMEM;
+
+	for_each_property_of_node(of_node, prop) {
+		char name[32]; /* 32 is max size of property name */
+		size_t len;
+
+		p = strstr(prop->name, SUPPLY_SUFFIX);
+		if (!p || p == prop->name)
+			continue;
+		len = strlen(prop->name) - strlen(SUPPLY_SUFFIX) + 1;
+		strlcpy(name, prop->name, len);
+
+		regulator = regulator_get_optional(&pdev->dev, name);
+		if (IS_ERR(regulator)) {
+			ret = PTR_ERR(regulator);
+			if (ret == -EPROBE_DEFER)
+				goto err;
+			drm_err(dev, "regulator %s not found: %d\n",
+				name, ret);
+			continue;
+		}
+
+		ret = regulator_enable(regulator);
+		if (ret) {
+			drm_err(dev, "failed to enable regulator %u: %d\n",
+				i, ret);
+			regulator_put(regulator);
+		}
+
+		sdev->regulators[i++] = regulator;
+	}
+	sdev->regulator_count = i;
+
+	return devm_add_action_or_reset(&pdev->dev,
+					simplekms_device_release_regulators,
+					sdev);
+
+err:
+	while (i) {
+		--i;
+		if (sdev->regulators[i]) {
+			regulator_disable(sdev->regulators[i]);
+			regulator_put(sdev->regulators[i]);
+		}
+	}
+	return ret;
+}
+#else
+static int simplekms_device_init_regulators(struct simplekms_device *sdev)
+{
+	return 0;
+}
+#endif
+
 /*
  *  Simplefb settings
  */
@@ -611,6 +736,9 @@ simplekms_device_create(struct drm_driver *drv, struct platform_device *pdev)
 	sdev->pdev = pdev;
 
 	ret = simplekms_device_init_clocks(sdev);
+	if (ret)
+		return ERR_PTR(ret);
+	ret = simplekms_device_init_regulators(sdev);
 	if (ret)
 		return ERR_PTR(ret);
 	ret = simplekms_device_init_fb(sdev);
-- 
2.27.0