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>

3 files changed, 277 insertions, 1 deletions

diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
index 54a3c298247b..0a7a470ee859 100644
--- a/drivers/nvmem/Kconfig
+++ b/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
diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
index 27e96a8efd1c..4e8c61628f1a 100644
--- a/drivers/nvmem/Makefile
+++ b/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
diff --git a/drivers/nvmem/sc27xx-efuse.c b/drivers/nvmem/sc27xx-efuse.c
new file mode 100644
index 000000000000..33185d8d82cf
--- /dev/null
+++ b/drivers/nvmem/sc27xx-efuse.c
@@ -0,0 +1,264 @@
+// 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");