bus: imx-weim: add DT overlay support for WEIM bus

Add OF reconfiguration notifier handler for WEIM bus to setup Chip
Select timings on runtime creation of child devices.

However, it is not possible to load another DT overlay with conflicting
CS timings with previously loaded overlay, even if the first one is
unloaded. The reason is that there is no acces to CS timing property of
a device node being removed, thus we can't track which of configured CS
are available for re-configuration.
Signed-off-by: Ivan Bornyakov <i.bornyakov@metrotek.ru>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

drivers/bus/imx-weim.c

@@ -64,6 +64,11 @@ struct cs_timing_state {
 	struct cs_timing cs[MAX_CS_COUNT];
 };
 
+struct weim_priv {
+	void __iomem *base;
+	struct cs_timing_state timing_state;
+};
+
 static const struct of_device_id weim_id_table[] = {
 	/* i.MX1/21 */
 	{ .compatible = "fsl,imx1-weim", .data = &imx1_weim_devtype, },
@@ -128,21 +133,26 @@ static int imx_weim_gpr_setup(struct platform_device *pdev)
 }
 
 /* Parse and set the timing for this device. */
-static int weim_timing_setup(struct device *dev,
-			     struct device_node *np, void __iomem *base,
-			     const struct imx_weim_devtype *devtype,
-			     struct cs_timing_state *ts)
+static int weim_timing_setup(struct device *dev, struct device_node *np,
+			     const struct imx_weim_devtype *devtype)
 {
 	u32 cs_idx, value[MAX_CS_REGS_COUNT];
 	int i, ret;
 	int reg_idx, num_regs;
 	struct cs_timing *cst;
+	struct weim_priv *priv;
+	struct cs_timing_state *ts;
+	void __iomem *base;
 
 	if (WARN_ON(devtype->cs_regs_count > MAX_CS_REGS_COUNT))
 		return -EINVAL;
 	if (WARN_ON(devtype->cs_count > MAX_CS_COUNT))
 		return -EINVAL;
 
+	priv = dev_get_drvdata(dev);
+	base = priv->base;
+	ts = &priv->timing_state;
+
 	ret = of_property_read_u32_array(np, "fsl,weim-cs-timing",
 					 value, devtype->cs_regs_count);
 	if (ret)
@@ -189,14 +199,15 @@ static int weim_timing_setup(struct device *dev,
 	return 0;
 }
 
-static int weim_parse_dt(struct platform_device *pdev, void __iomem *base)
+static int weim_parse_dt(struct platform_device *pdev)
 {
 	const struct of_device_id *of_id = of_match_device(weim_id_table,
 							   &pdev->dev);
 	const struct imx_weim_devtype *devtype = of_id->data;
 	struct device_node *child;
 	int ret, have_child = 0;
-	struct cs_timing_state ts = {};
+	struct weim_priv *priv;
+	void __iomem *base;
 	u32 reg;
 
 	if (devtype == &imx50_weim_devtype) {
@@ -205,6 +216,9 @@ static int weim_parse_dt(struct platform_device *pdev, void __iomem *base)
 			return ret;
 	}
 
+	priv = dev_get_drvdata(&pdev->dev);
+	base = priv->base;
+
 	if (of_property_read_bool(pdev->dev.of_node, "fsl,burst-clk-enable")) {
 		if (devtype->wcr_bcm) {
 			reg = readl(base + devtype->wcr_offset);
@@ -229,7 +243,7 @@ static int weim_parse_dt(struct platform_device *pdev, void __iomem *base)
 	}
 
 	for_each_available_child_of_node(pdev->dev.of_node, child) {
-		ret = weim_timing_setup(&pdev->dev, child, base, devtype, &ts);
+		ret = weim_timing_setup(&pdev->dev, child, devtype);
 		if (ret)
 			dev_warn(&pdev->dev, "%pOF set timing failed.\n",
 				child);
@@ -248,17 +262,25 @@ static int weim_parse_dt(struct platform_device *pdev, void __iomem *base)
 
 static int weim_probe(struct platform_device *pdev)
 {
+	struct weim_priv *priv;
 	struct resource *res;
 	struct clk *clk;
 	void __iomem *base;
 	int ret;
 
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
 	/* get the resource */
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	base = devm_ioremap_resource(&pdev->dev, res);
 	if (IS_ERR(base))
 		return PTR_ERR(base);
 
+	priv->base = base;
+	dev_set_drvdata(&pdev->dev, priv);
+
 	/* get the clock */
 	clk = devm_clk_get(&pdev->dev, NULL);
 	if (IS_ERR(clk))
@@ -269,7 +291,7 @@ static int weim_probe(struct platform_device *pdev)
 		return ret;
 
 	/* parse the device node */
-	ret = weim_parse_dt(pdev, base);
+	ret = weim_parse_dt(pdev);
 	if (ret)
 		clk_disable_unprepare(clk);
 	else
@@ -278,6 +300,81 @@ static int weim_probe(struct platform_device *pdev)
 	return ret;
 }
 
+#if IS_ENABLED(CONFIG_OF_DYNAMIC)
+static int of_weim_notify(struct notifier_block *nb, unsigned long action,
+			  void *arg)
+{
+	const struct imx_weim_devtype *devtype;
+	struct of_reconfig_data *rd = arg;
+	const struct of_device_id *of_id;
+	struct platform_device *pdev;
+	int ret = NOTIFY_OK;
+
+	switch (of_reconfig_get_state_change(action, rd)) {
+	case OF_RECONFIG_CHANGE_ADD:
+		of_id = of_match_node(weim_id_table, rd->dn->parent);
+		if (!of_id)
+			return NOTIFY_OK; /* not for us */
+
+		devtype = of_id->data;
+
+		pdev = of_find_device_by_node(rd->dn->parent);
+		if (!pdev) {
+			pr_err("%s: could not find platform device for '%pOF'\n",
+				__func__, rd->dn->parent);
+
+			return notifier_from_errno(-EINVAL);
+		}
+
+		if (weim_timing_setup(&pdev->dev, rd->dn, devtype))
+			dev_warn(&pdev->dev,
+				 "Failed to setup timing for '%pOF'\n", rd->dn);
+
+		if (!of_node_check_flag(rd->dn, OF_POPULATED)) {
+			if (!of_platform_device_create(rd->dn, NULL, &pdev->dev)) {
+				dev_err(&pdev->dev,
+					"Failed to create child device '%pOF'\n",
+					rd->dn);
+				ret = notifier_from_errno(-EINVAL);
+			}
+		}
+
+		platform_device_put(pdev);
+
+		break;
+	case OF_RECONFIG_CHANGE_REMOVE:
+		if (!of_node_check_flag(rd->dn, OF_POPULATED))
+			return NOTIFY_OK; /* device already destroyed */
+
+		of_id = of_match_node(weim_id_table, rd->dn->parent);
+		if (!of_id)
+			return NOTIFY_OK; /* not for us */
+
+		pdev = of_find_device_by_node(rd->dn);
+		if (!pdev) {
+			dev_err(&pdev->dev,
+				"Could not find platform device for '%pOF'\n",
+				rd->dn);
+
+			ret = notifier_from_errno(-EINVAL);
+		} else {
+			of_platform_device_destroy(&pdev->dev, NULL);
+			platform_device_put(pdev);
+		}
+
+		break;
+	default:
+		break;
+	}
+
+	return ret;
+}
+
+struct notifier_block weim_of_notifier = {
+	.notifier_call = of_weim_notify,
+};
+#endif /* IS_ENABLED(CONFIG_OF_DYNAMIC) */
+
 static struct platform_driver weim_driver = {
 	.driver = {
 		.name		= "imx-weim",
@@ -285,7 +382,27 @@ static struct platform_driver weim_driver = {
 	},
 	.probe = weim_probe,
 };
-module_platform_driver(weim_driver);
+
+static int __init weim_init(void)
+{
+#if IS_ENABLED(CONFIG_OF_DYNAMIC)
+	WARN_ON(of_reconfig_notifier_register(&weim_of_notifier));
+#endif /* IS_ENABLED(CONFIG_OF_DYNAMIC) */
+
+	return platform_driver_register(&weim_driver);
+}
+module_init(weim_init);
+
+static void __exit weim_exit(void)
+{
+#if IS_ENABLED(CONFIG_OF_DYNAMIC)
+	of_reconfig_notifier_unregister(&weim_of_notifier);
+#endif /* IS_ENABLED(CONFIG_OF_DYNAMIC) */
+
+	return platform_driver_unregister(&weim_driver);
+
+}
+module_exit(weim_exit);
 
 MODULE_AUTHOR("Freescale Semiconductor Inc.");
 MODULE_DESCRIPTION("i.MX EIM Controller Driver");