nvmem: Add Spreadtrum SC27XX efuse support

This patch add the efuse driver which is embeded in Spreadtrum SC27XX
series PMICs. The sc27xx efuse contains 32 blocks and each block's
data width is 16 bits.
Signed-off-by: Freeman Liu <freeman.liu@spreadtrum.com>
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/nvmem/Kconfig

@@ -181,4 +181,15 @@ config RAVE_SP_EEPROM
 	help
 	  Say y here to enable Rave SP EEPROM support.
 
+config SC27XX_EFUSE
+	tristate "Spreadtrum SC27XX eFuse Support"
+	depends on MFD_SC27XX_PMIC || COMPILE_TEST
+	depends on HAS_IOMEM
+	help
+	  This is a simple driver to dump specified values of Spreadtrum
+	  SC27XX PMICs from eFuse.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called nvmem-sc27xx-efuse.
+
 endif

drivers/nvmem/Makefile

@@ -39,4 +39,5 @@ obj-$(CONFIG_NVMEM_SNVS_LPGPR)	+= nvmem_snvs_lpgpr.o
 nvmem_snvs_lpgpr-y		:= snvs_lpgpr.o
 obj-$(CONFIG_RAVE_SP_EEPROM)	+= nvmem-rave-sp-eeprom.o
 nvmem-rave-sp-eeprom-y		:= rave-sp-eeprom.o
-
+obj-$(CONFIG_SC27XX_EFUSE)	+= nvmem-sc27xx-efuse.o
+nvmem-sc27xx-efuse-y		:= sc27xx-efuse.o

drivers/nvmem/sc27xx-efuse.c

+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2018 Spreadtrum Communications Inc.
+
+#include <linux/hwspinlock.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/nvmem-provider.h>
+
+/* PMIC global registers definition */
+#define SC27XX_MODULE_EN		0xc08
+#define SC27XX_EFUSE_EN			BIT(6)
+
+/* Efuse controller registers definition */
+#define SC27XX_EFUSE_GLB_CTRL		0x0
+#define SC27XX_EFUSE_DATA_RD		0x4
+#define SC27XX_EFUSE_DATA_WR		0x8
+#define SC27XX_EFUSE_BLOCK_INDEX	0xc
+#define SC27XX_EFUSE_MODE_CTRL		0x10
+#define SC27XX_EFUSE_STATUS		0x14
+#define SC27XX_EFUSE_WR_TIMING_CTRL	0x20
+#define SC27XX_EFUSE_RD_TIMING_CTRL	0x24
+#define SC27XX_EFUSE_EFUSE_DEB_CTRL	0x28
+
+/* Mask definition for SC27XX_EFUSE_BLOCK_INDEX register */
+#define SC27XX_EFUSE_BLOCK_MASK		GENMASK(4, 0)
+
+/* Bits definitions for SC27XX_EFUSE_MODE_CTRL register */
+#define SC27XX_EFUSE_PG_START		BIT(0)
+#define SC27XX_EFUSE_RD_START		BIT(1)
+#define SC27XX_EFUSE_CLR_RDDONE		BIT(2)
+
+/* Bits definitions for SC27XX_EFUSE_STATUS register */
+#define SC27XX_EFUSE_PGM_BUSY		BIT(0)
+#define SC27XX_EFUSE_READ_BUSY		BIT(1)
+#define SC27XX_EFUSE_STANDBY		BIT(2)
+#define SC27XX_EFUSE_GLOBAL_PROT	BIT(3)
+#define SC27XX_EFUSE_RD_DONE		BIT(4)
+
+/* Block number and block width (bytes) definitions */
+#define SC27XX_EFUSE_BLOCK_MAX		32
+#define SC27XX_EFUSE_BLOCK_WIDTH	2
+
+/* Timeout (ms) for the trylock of hardware spinlocks */
+#define SC27XX_EFUSE_HWLOCK_TIMEOUT	5000
+
+/* Timeout (us) of polling the status */
+#define SC27XX_EFUSE_POLL_TIMEOUT	3000000
+#define SC27XX_EFUSE_POLL_DELAY_US	10000
+
+struct sc27xx_efuse {
+	struct device *dev;
+	struct regmap *regmap;
+	struct hwspinlock *hwlock;
+	struct mutex mutex;
+	u32 base;
+};
+
+/*
+ * On Spreadtrum platform, we have multi-subsystems will access the unique
+ * efuse controller, so we need one hardware spinlock to synchronize between
+ * the multiple subsystems.
+ */
+static int sc27xx_efuse_lock(struct sc27xx_efuse *efuse)
+{
+	int ret;
+
+	mutex_lock(&efuse->mutex);
+
+	ret = hwspin_lock_timeout_raw(efuse->hwlock,
+				      SC27XX_EFUSE_HWLOCK_TIMEOUT);
+	if (ret) {
+		dev_err(efuse->dev, "timeout to get the hwspinlock\n");
+		mutex_unlock(&efuse->mutex);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void sc27xx_efuse_unlock(struct sc27xx_efuse *efuse)
+{
+	hwspin_unlock_raw(efuse->hwlock);
+	mutex_unlock(&efuse->mutex);
+}
+
+static int sc27xx_efuse_poll_status(struct sc27xx_efuse *efuse, u32 bits)
+{
+	int ret;
+	u32 val;
+
+	ret = regmap_read_poll_timeout(efuse->regmap,
+				       efuse->base + SC27XX_EFUSE_STATUS,
+				       val, (val & bits),
+				       SC27XX_EFUSE_POLL_DELAY_US,
+				       SC27XX_EFUSE_POLL_TIMEOUT);
+	if (ret) {
+		dev_err(efuse->dev, "timeout to update the efuse status\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static int sc27xx_efuse_read(void *context, u32 offset, void *val, size_t bytes)
+{
+	struct sc27xx_efuse *efuse = context;
+	u32 buf;
+	int ret;
+
+	if (offset > SC27XX_EFUSE_BLOCK_MAX || bytes > SC27XX_EFUSE_BLOCK_WIDTH)
+		return -EINVAL;
+
+	ret = sc27xx_efuse_lock(efuse);
+	if (ret)
+		return ret;
+
+	/* Enable the efuse controller. */
+	ret = regmap_update_bits(efuse->regmap, SC27XX_MODULE_EN,
+				 SC27XX_EFUSE_EN, SC27XX_EFUSE_EN);
+	if (ret)
+		goto unlock_efuse;
+
+	/*
+	 * Before reading, we should ensure the efuse controller is in
+	 * standby state.
+	 */
+	ret = sc27xx_efuse_poll_status(efuse, SC27XX_EFUSE_STANDBY);
+	if (ret)
+		goto disable_efuse;
+
+	/* Set the block address to be read. */
+	ret = regmap_write(efuse->regmap,
+			   efuse->base + SC27XX_EFUSE_BLOCK_INDEX,
+			   offset & SC27XX_EFUSE_BLOCK_MASK);
+	if (ret)
+		goto disable_efuse;
+
+	/* Start reading process from efuse memory. */
+	ret = regmap_update_bits(efuse->regmap,
+				 efuse->base + SC27XX_EFUSE_MODE_CTRL,
+				 SC27XX_EFUSE_RD_START,
+				 SC27XX_EFUSE_RD_START);
+	if (ret)
+		goto disable_efuse;
+
+	/*
+	 * Polling the read done status to make sure the reading process
+	 * is completed, that means the data can be read out now.
+	 */
+	ret = sc27xx_efuse_poll_status(efuse, SC27XX_EFUSE_RD_DONE);
+	if (ret)
+		goto disable_efuse;
+
+	/* Read data from efuse memory. */
+	ret = regmap_read(efuse->regmap, efuse->base + SC27XX_EFUSE_DATA_RD,
+			  &buf);
+	if (ret)
+		goto disable_efuse;
+
+	/* Clear the read done flag. */
+	ret = regmap_update_bits(efuse->regmap,
+				 efuse->base + SC27XX_EFUSE_MODE_CTRL,
+				 SC27XX_EFUSE_CLR_RDDONE,
+				 SC27XX_EFUSE_CLR_RDDONE);
+
+disable_efuse:
+	/* Disable the efuse controller after reading. */
+	regmap_update_bits(efuse->regmap, SC27XX_MODULE_EN, SC27XX_EFUSE_EN, 0);
+unlock_efuse:
+	sc27xx_efuse_unlock(efuse);
+
+	if (!ret)
+		memcpy(val, &buf, bytes);
+
+	return ret;
+}
+
+static int sc27xx_efuse_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct nvmem_config econfig = { };
+	struct nvmem_device *nvmem;
+	struct sc27xx_efuse *efuse;
+	int ret;
+
+	efuse = devm_kzalloc(&pdev->dev, sizeof(*efuse), GFP_KERNEL);
+	if (!efuse)
+		return -ENOMEM;
+
+	efuse->regmap = dev_get_regmap(pdev->dev.parent, NULL);
+	if (!efuse->regmap) {
+		dev_err(&pdev->dev, "failed to get efuse regmap\n");
+		return -ENODEV;
+	}
+
+	ret = of_property_read_u32(np, "reg", &efuse->base);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to get efuse base address\n");
+		return ret;
+	}
+
+	ret = of_hwspin_lock_get_id(np, 0);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "failed to get hwspinlock id\n");
+		return ret;
+	}
+
+	efuse->hwlock = hwspin_lock_request_specific(ret);
+	if (!efuse->hwlock) {
+		dev_err(&pdev->dev, "failed to request hwspinlock\n");
+		return -ENXIO;
+	}
+
+	mutex_init(&efuse->mutex);
+	efuse->dev = &pdev->dev;
+	platform_set_drvdata(pdev, efuse);
+
+	econfig.stride = 1;
+	econfig.word_size = 1;
+	econfig.read_only = true;
+	econfig.name = "sc27xx-efuse";
+	econfig.size = SC27XX_EFUSE_BLOCK_MAX * SC27XX_EFUSE_BLOCK_WIDTH;
+	econfig.reg_read = sc27xx_efuse_read;
+	econfig.priv = efuse;
+	econfig.dev = &pdev->dev;
+	nvmem = devm_nvmem_register(&pdev->dev, &econfig);
+	if (IS_ERR(nvmem)) {
+		dev_err(&pdev->dev, "failed to register nvmem config\n");
+		hwspin_lock_free(efuse->hwlock);
+		return PTR_ERR(nvmem);
+	}
+
+	return 0;
+}
+
+static int sc27xx_efuse_remove(struct platform_device *pdev)
+{
+	struct sc27xx_efuse *efuse = platform_get_drvdata(pdev);
+
+	hwspin_lock_free(efuse->hwlock);
+	return 0;
+}
+
+static const struct of_device_id sc27xx_efuse_of_match[] = {
+	{ .compatible = "sprd,sc2731-efuse" },
+	{ }
+};
+
+static struct platform_driver sc27xx_efuse_driver = {
+	.probe = sc27xx_efuse_probe,
+	.remove = sc27xx_efuse_remove,
+	.driver = {
+		.name = "sc27xx-efuse",
+		.of_match_table = sc27xx_efuse_of_match,
+	},
+};
+
+module_platform_driver(sc27xx_efuse_driver);
+
+MODULE_AUTHOR("Freeman Liu <freeman.liu@spreadtrum.com>");
+MODULE_DESCRIPTION("Spreadtrum SC27xx efuse driver");
+MODULE_LICENSE("GPL v2");