[PATCH 2/3] soc: ti: k3-socinfo: Export SoC registration helper

[Moteen Shah <m-shah@ti.com>]

The k3-socinfo driver reads the JTAG ID through a dedicated MMIO region and
then decodes it and registers the SoC device.

Newer TI SoCs like TDA54 use a different path for accessing the JTAG ID
register, but the decoding of the JTAG ID into the SoC information remains
the same.

Split the decode and registration part out of k3_chipinfo_probe() into
k3_socinfo_register() and export it, so that other drivers can register the
SoC device once they have read the JTAG ID through their own access path.

Since the helper can now be called from modular drivers, it must not leak
the SoC device when the caller goes away. Tie the registration to the
calling device with a devm action, which unregisters the SoC device and
frees its attributes on unbind. Callers need no unregister counterpart and
the helper keeps returning an int. If the soc bus is not up yet, the
attributes are only parked for later registration and there is nothing to
undo, so no action is added in that case.

Signed-off-by: Moteen Shah <m-shah@ti.com>
---
 drivers/soc/ti/k3-socinfo.c       | 101 +++++++++++++++++++++++-------
 include/linux/soc/ti/k3-socinfo.h |  11 ++++
 2 files changed, 90 insertions(+), 22 deletions(-)
 create mode 100644 include/linux/soc/ti/k3-socinfo.h

diff --git a/drivers/soc/ti/k3-socinfo.c b/drivers/soc/ti/k3-socinfo.c
index 48dbef3acceb4..5fae03004e350 100644
--- a/drivers/soc/ti/k3-socinfo.c
+++ b/drivers/soc/ti/k3-socinfo.c
@@ -5,6 +5,8 @@
  * Copyright (C) 2020 Texas Instruments Incorporated - http://www.ti.com
  */
 
+#include <linux/device.h>
+#include <linux/export.h>
 #include <linux/mfd/syscon.h>
 #include <linux/nvmem-consumer.h>
 #include <linux/of.h>
@@ -12,6 +14,7 @@
 #include <linux/regmap.h>
 #include <linux/platform_device.h>
 #include <linux/slab.h>
+#include <linux/soc/ti/k3-socinfo.h>
 #include <linux/string.h>
 #include <linux/sys_soc.h>
 
@@ -152,38 +155,44 @@ k3_chipinfo_variant_to_sr(struct device *dev, unsigned int partno,
 	return -ENODEV;
 }
 
-static const struct regmap_config k3_chipinfo_regmap_cfg = {
-	.reg_bits = 32,
-	.val_bits = 32,
-	.reg_stride = 4,
+struct k3_socinfo {
+	struct soc_device *soc_dev;
+	struct soc_device_attribute *soc_dev_attr;
 };
 
-static int k3_chipinfo_probe(struct platform_device *pdev)
+static void k3_socinfo_unregister(void *data)
+{
+	struct k3_socinfo *info = data;
+
+	soc_device_unregister(info->soc_dev);
+	/* The attributes must only be freed after the unregister. */
+	kfree(info->soc_dev_attr->revision);
+	kfree(info->soc_dev_attr);
+}
+
+/**
+ * k3_socinfo_register() - Decode a JTAG ID and register the SoC device
+ * @dev: device on whose behalf the SoC device is registered
+ * @jtag_id: raw JTAG ID register value read by the caller
+ *
+ * The registration is managed by @dev: the SoC device and its attributes are
+ * released automatically when @dev is unbound, so callers need no matching
+ * unregister call. If the soc bus is not yet available, the registration is
+ * deferred until it is and cannot be released by @dev.
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+int k3_socinfo_register(struct device *dev, u32 jtag_id)
 {
-	struct device_node *node = pdev->dev.of_node;
+	struct device_node *node;
+	struct k3_socinfo *info;
 	struct soc_device_attribute *soc_dev_attr;
-	struct device *dev = &pdev->dev;
 	struct soc_device *soc_dev;
-	struct regmap *regmap;
-	void __iomem *base;
 	u32 partno_id;
 	u32 variant;
-	u32 jtag_id;
 	u32 mfg;
 	int ret;
 
-	base = devm_platform_ioremap_resource(pdev, 0);
-	if (IS_ERR(base))
-		return PTR_ERR(base);
-
-	regmap = devm_regmap_init_mmio(dev, base, &k3_chipinfo_regmap_cfg);
-	if (IS_ERR(regmap))
-		return PTR_ERR(regmap);
-
-	ret = regmap_read(regmap, CTRLMMR_WKUP_JTAGID_REG, &jtag_id);
-	if (ret < 0)
-		return ret;
-
 	mfg = (jtag_id & CTRLMMR_WKUP_JTAGID_MFG_MASK) >>
 	       CTRLMMR_WKUP_JTAGID_MFG_SHIFT;
 
@@ -198,6 +207,10 @@ static int k3_chipinfo_probe(struct platform_device *pdev)
 	partno_id = (jtag_id & CTRLMMR_WKUP_JTAGID_PARTNO_MASK) >>
 		 CTRLMMR_WKUP_JTAGID_PARTNO_SHIFT;
 
+	info = devm_kzalloc(dev, sizeof(*info), GFP_KERNEL);
+	if (!info)
+		return -ENOMEM;
+
 	soc_dev_attr = kzalloc_obj(*soc_dev_attr);
 	if (!soc_dev_attr)
 		return -ENOMEM;
@@ -224,6 +237,20 @@ static int k3_chipinfo_probe(struct platform_device *pdev)
 		goto err_free_rev;
 	}
 
+	/*
+	 * A NULL handle means the soc bus is not up yet and the attributes
+	 * were parked for registration at soc bus init. They must stay
+	 * allocated and cannot be unregistered, so there is nothing to undo.
+	 */
+	if (soc_dev) {
+		info->soc_dev = soc_dev;
+		info->soc_dev_attr = soc_dev_attr;
+		ret = devm_add_action_or_reset(dev, k3_socinfo_unregister,
+					       info);
+		if (ret)
+			return ret;
+	}
+
 	dev_info(dev, "Family:%s rev:%s JTAGID[0x%08x] Detected\n",
 		 soc_dev_attr->family,
 		 soc_dev_attr->revision, jtag_id);
@@ -236,6 +263,36 @@ static int k3_chipinfo_probe(struct platform_device *pdev)
 	kfree(soc_dev_attr);
 	return ret;
 }
+EXPORT_SYMBOL_GPL(k3_socinfo_register);
+
+static const struct regmap_config k3_chipinfo_regmap_cfg = {
+	.reg_bits = 32,
+	.val_bits = 32,
+	.reg_stride = 4,
+};
+
+static int k3_chipinfo_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct regmap *regmap;
+	void __iomem *base;
+	u32 jtag_id;
+	int ret;
+
+	base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(base))
+		return PTR_ERR(base);
+
+	regmap = devm_regmap_init_mmio(dev, base, &k3_chipinfo_regmap_cfg);
+	if (IS_ERR(regmap))
+		return PTR_ERR(regmap);
+
+	ret = regmap_read(regmap, CTRLMMR_WKUP_JTAGID_REG, &jtag_id);
+	if (ret < 0)
+		return ret;
+
+	return k3_socinfo_register(dev, jtag_id);
+}
 
 static const struct of_device_id k3_chipinfo_of_match[] = {
 	{ .compatible = "ti,am654-chipid", },
diff --git a/include/linux/soc/ti/k3-socinfo.h b/include/linux/soc/ti/k3-socinfo.h
new file mode 100644
index 0000000000000..487e69d0069d1
--- /dev/null
+++ b/include/linux/soc/ti/k3-socinfo.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LINUX_SOC_TI_K3_SOCINFO_H__
+#define __LINUX_SOC_TI_K3_SOCINFO_H__
+
+#include <linux/types.h>
+
+struct device;
+
+int k3_socinfo_register(struct device *dev, u32 jtag_id);
+
+#endif /* __LINUX_SOC_TI_K3_SOCINFO_H__ */
-- 
2.34.1