nvmem: add driver for JZ4780 efuse

This patch brings support for the JZ4780 efuse. Currently it only exposes
a read only access to the entire 8K bits efuse memory and nvmem cells.

To fetch for example the MAC address:

dd if=/sys/devices/platform/134100d0.efuse/jz4780-efuse0/nvmem bs=1 skip=34 count=6 status=none | xxd

Tested-by: Mathieu Malaterre <malat@debian.org>
Signed-off-by: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
Signed-off-by: Mathieu Malaterre <malat@debian.org>
Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20200310132257.23358-13-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 239 insertions, 0 deletions

diff --git a/drivers/nvmem/jz4780-efuse.c b/drivers/nvmem/jz4780-efuse.c
new file mode 100644
index 000000000000..51d140980b1e
--- /dev/null
+++ b/drivers/nvmem/jz4780-efuse.c
@@ -0,0 +1,239 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * JZ4780 EFUSE Memory Support driver
+ *
+ * Copyright (c) 2017 PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
+ * Copyright (c) 2020 H. Nikolaus Schaller <hns@goldelico.com>
+ */
+
+/*
+ * Currently supports JZ4780 efuse which has 8K programmable bit.
+ * Efuse is separated into seven segments as below:
+ *
+ * -----------------------------------------------------------------------
+ * | 64 bit | 128 bit | 128 bit | 3520 bit | 8 bit | 2296 bit | 2048 bit |
+ * -----------------------------------------------------------------------
+ *
+ * The rom itself is accessed using a 9 bit address line and an 8 word wide bus
+ * which reads/writes based on strobes. The strobe is configured in the config
+ * register and is based on number of cycles of the bus clock.
+ *
+ * Driver supports read only as the writes are done in the Factory.
+ */
+
+#include <linux/bitops.h>
+#include <linux/clk.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/timer.h>
+
+#define JZ_EFUCTRL		(0x0)	/* Control Register */
+#define JZ_EFUCFG		(0x4)	/* Configure Register*/
+#define JZ_EFUSTATE		(0x8)	/* Status Register */
+#define JZ_EFUDATA(n)		(0xC + (n) * 4)
+
+/* We read 32 byte chunks to avoid complexity in the driver. */
+#define JZ_EFU_READ_SIZE 32
+
+#define EFUCTRL_ADDR_MASK	0x3FF
+#define EFUCTRL_ADDR_SHIFT	21
+#define EFUCTRL_LEN_MASK	0x1F
+#define EFUCTRL_LEN_SHIFT	16
+#define EFUCTRL_PG_EN		BIT(15)
+#define EFUCTRL_WR_EN		BIT(1)
+#define EFUCTRL_RD_EN		BIT(0)
+
+#define EFUCFG_INT_EN		BIT(31)
+#define EFUCFG_RD_ADJ_MASK	0xF
+#define EFUCFG_RD_ADJ_SHIFT	20
+#define EFUCFG_RD_STR_MASK	0xF
+#define EFUCFG_RD_STR_SHIFT	16
+#define EFUCFG_WR_ADJ_MASK	0xF
+#define EFUCFG_WR_ADJ_SHIFT	12
+#define EFUCFG_WR_STR_MASK	0xFFF
+#define EFUCFG_WR_STR_SHIFT	0
+
+#define EFUSTATE_WR_DONE	BIT(1)
+#define EFUSTATE_RD_DONE	BIT(0)
+
+struct jz4780_efuse {
+	struct device *dev;
+	struct regmap *map;
+	struct clk *clk;
+};
+
+/* main entry point */
+static int jz4780_efuse_read(void *context, unsigned int offset,
+			     void *val, size_t bytes)
+{
+	struct jz4780_efuse *efuse = context;
+
+	while (bytes > 0) {
+		unsigned int start = offset & ~(JZ_EFU_READ_SIZE - 1);
+		unsigned int chunk = min(bytes, (start + JZ_EFU_READ_SIZE)
+					 - offset);
+		char buf[JZ_EFU_READ_SIZE];
+		unsigned int tmp;
+		u32 ctrl;
+		int ret;
+
+		ctrl = (start << EFUCTRL_ADDR_SHIFT)
+			| ((JZ_EFU_READ_SIZE - 1) << EFUCTRL_LEN_SHIFT)
+			| EFUCTRL_RD_EN;
+
+		regmap_update_bits(efuse->map, JZ_EFUCTRL,
+				   (EFUCTRL_ADDR_MASK << EFUCTRL_ADDR_SHIFT) |
+				   (EFUCTRL_LEN_MASK << EFUCTRL_LEN_SHIFT) |
+				   EFUCTRL_PG_EN | EFUCTRL_WR_EN |
+				   EFUCTRL_RD_EN,
+				   ctrl);
+
+		ret = regmap_read_poll_timeout(efuse->map, JZ_EFUSTATE,
+					       tmp, tmp & EFUSTATE_RD_DONE,
+					       1 * MSEC_PER_SEC,
+					       50 * MSEC_PER_SEC);
+		if (ret < 0) {
+			dev_err(efuse->dev, "Time out while reading efuse data");
+			return ret;
+		}
+
+		ret = regmap_bulk_read(efuse->map, JZ_EFUDATA(0),
+				       buf, JZ_EFU_READ_SIZE / sizeof(u32));
+		if (ret < 0)
+			return ret;
+
+		memcpy(val, &buf[offset - start], chunk);
+
+		val += chunk;
+		offset += chunk;
+		bytes -= chunk;
+	}
+
+	return 0;
+}
+
+static struct nvmem_config jz4780_efuse_nvmem_config = {
+	.name = "jz4780-efuse",
+	.size = 1024,
+	.word_size = 1,
+	.stride = 1,
+	.owner = THIS_MODULE,
+	.reg_read = jz4780_efuse_read,
+};
+
+static const struct regmap_config jz4780_efuse_regmap_config = {
+	.reg_bits = 32,
+	.val_bits = 32,
+	.reg_stride = 4,
+	.max_register = JZ_EFUDATA(7),
+};
+
+static void clk_disable_unprepare_helper(void *clock)
+{
+	clk_disable_unprepare(clock);
+}
+
+static int jz4780_efuse_probe(struct platform_device *pdev)
+{
+	struct nvmem_device *nvmem;
+	struct jz4780_efuse *efuse;
+	struct nvmem_config cfg;
+	unsigned long clk_rate;
+	unsigned long rd_adj;
+	unsigned long rd_strobe;
+	struct device *dev = &pdev->dev;
+	void __iomem *regs;
+	int ret;
+
+	efuse = devm_kzalloc(dev, sizeof(*efuse), GFP_KERNEL);
+	if (!efuse)
+		return -ENOMEM;
+
+	regs = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(regs))
+		return PTR_ERR(regs);
+
+	efuse->map = devm_regmap_init_mmio(dev, regs,
+					   &jz4780_efuse_regmap_config);
+	if (IS_ERR(efuse->map))
+		return PTR_ERR(efuse->map);
+
+	efuse->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(efuse->clk))
+		return PTR_ERR(efuse->clk);
+
+	ret = clk_prepare_enable(efuse->clk);
+	if (ret < 0)
+		return ret;
+
+	ret = devm_add_action_or_reset(&pdev->dev,
+				       clk_disable_unprepare_helper,
+				       efuse->clk);
+	if (ret < 0)
+		return ret;
+
+	clk_rate = clk_get_rate(efuse->clk);
+
+	efuse->dev = dev;
+
+	/*
+	 * rd_adj and rd_strobe are 4 bit values
+	 * conditions:
+	 *   bus clk_period * (rd_adj + 1) > 6.5ns
+	 *   bus clk_period * (rd_adj + 5 + rd_strobe) > 35ns
+	 *   i.e. rd_adj >= 6.5ns / clk_period
+	 *   i.e. rd_strobe >= 35 ns / clk_period - 5 - rd_adj + 1
+	 * constants:
+	 *   1 / 6.5ns == 153846154 Hz
+	 *   1 / 35ns == 28571429 Hz
+	 */
+
+	rd_adj = clk_rate / 153846154;
+	rd_strobe = clk_rate / 28571429 - 5 - rd_adj + 1;
+
+	if (rd_adj > EFUCFG_RD_ADJ_MASK ||
+	    rd_strobe > EFUCFG_RD_STR_MASK) {
+		dev_err(&pdev->dev, "Cannot set clock configuration\n");
+		return -EINVAL;
+	}
+
+	regmap_update_bits(efuse->map, JZ_EFUCFG,
+			   (EFUCFG_RD_ADJ_MASK << EFUCFG_RD_ADJ_SHIFT) |
+			   (EFUCFG_RD_STR_MASK << EFUCFG_RD_STR_SHIFT),
+			   (rd_adj << EFUCFG_RD_ADJ_SHIFT) |
+			   (rd_strobe << EFUCFG_RD_STR_SHIFT));
+
+	cfg = jz4780_efuse_nvmem_config;
+	cfg.dev = &pdev->dev;
+	cfg.priv = efuse;
+
+	nvmem = devm_nvmem_register(dev, &cfg);
+	if (IS_ERR(nvmem))
+		return PTR_ERR(nvmem);
+
+	return 0;
+}
+
+static const struct of_device_id jz4780_efuse_match[] = {
+	{ .compatible = "ingenic,jz4780-efuse" },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, jz4780_efuse_match);
+
+static struct platform_driver jz4780_efuse_driver = {
+	.probe  = jz4780_efuse_probe,
+	.driver = {
+		.name = "jz4780-efuse",
+		.of_match_table = jz4780_efuse_match,
+	},
+};
+module_platform_driver(jz4780_efuse_driver);
+
+MODULE_AUTHOR("PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>");
+MODULE_AUTHOR("H. Nikolaus Schaller <hns@goldelico.com>");
+MODULE_AUTHOR("Paul Cercueil <paul@crapouillou.net>");
+MODULE_DESCRIPTION("Ingenic JZ4780 efuse driver");
+MODULE_LICENSE("GPL v2");