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Subject[PATCH 2/2] nvmem: add snvs_lpgpr driver
Date
From: Oleksij Rempel <o.rempel@pengutronix.de>

This is a driver for Low Power General Purpose Register (LPGPR)
available on i.MX6 SoCs in Secure Non-Volatile Storage (SNVS)
of this chip.

It is a 32-bit read/write register located in the low power domain.
Since LPGPR is located in the battery-backed power domain, LPGPR can
be used by any application for retaining data during an SoC power-down
mode.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
---
drivers/nvmem/Kconfig | 10 +++
drivers/nvmem/Makefile | 2 +
drivers/nvmem/snvs_lpgpr.c | 156 +++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 168 insertions(+)
create mode 100644 drivers/nvmem/snvs_lpgpr.c

diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
index 101ced4c84be..ea3044c5d6ee 100644
--- a/drivers/nvmem/Kconfig
+++ b/drivers/nvmem/Kconfig
@@ -144,4 +144,14 @@ config MESON_EFUSE
This driver can also be built as a module. If so, the module
will be called nvmem_meson_efuse.

+config NVMEM_SNVS_LPGPR
+ tristate "Support for Low Power General Purpose Register"
+ depends on SOC_IMX6 || COMPILE_TEST
+ help
+ This is a driver for Low Power General Purpose Register (LPGPR) available on
+ i.MX6 SoCs in Secure Non-Volatile Storage (SNVS) of this chip.
+
+ This driver can also be built as a module. If so, the module
+ will be called nvmem-snvs-lpgpr.
+
endif
diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
index 173140658693..4c589184acee 100644
--- a/drivers/nvmem/Makefile
+++ b/drivers/nvmem/Makefile
@@ -30,3 +30,5 @@ obj-$(CONFIG_NVMEM_VF610_OCOTP) += nvmem-vf610-ocotp.o
nvmem-vf610-ocotp-y := vf610-ocotp.o
obj-$(CONFIG_MESON_EFUSE) += nvmem_meson_efuse.o
nvmem_meson_efuse-y := meson-efuse.o
+obj-$(CONFIG_NVMEM_SNVS_LPGPR) += nvmem_snvs_lpgpr.o
+nvmem_snvs_lpgpr-y := snvs_lpgpr.o
diff --git a/drivers/nvmem/snvs_lpgpr.c b/drivers/nvmem/snvs_lpgpr.c
new file mode 100644
index 000000000000..e5c2a4a17f03
--- /dev/null
+++ b/drivers/nvmem/snvs_lpgpr.c
@@ -0,0 +1,156 @@
+/*
+ * Copyright (c) 2015 Pengutronix, Steffen Trumtrar <kernel@pengutronix.de>
+ * Copyright (c) 2017 Pengutronix, Oleksij Rempel <kernel@pengutronix.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation.
+ */
+
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/of_device.h>
+#include <linux/regmap.h>
+
+#define IMX6Q_SNVS_HPLR 0x00
+#define IMX6Q_GPR_SL BIT(5)
+#define IMX6Q_SNVS_LPLR 0x34
+#define IMX6Q_GPR_HL BIT(5)
+#define IMX6Q_SNVS_LPGPR 0x68
+
+struct snvs_lpgpr_cfg {
+ int offset;
+ int offset_hplr;
+ int offset_lplr;
+};
+
+struct snvs_lpgpr_priv {
+ struct device_d *dev;
+ struct regmap *regmap;
+ struct nvmem_config cfg;
+ const struct snvs_lpgpr_cfg *dcfg;
+};
+
+static const struct snvs_lpgpr_cfg snvs_lpgpr_cfg_imx6q = {
+ .offset = IMX6Q_SNVS_LPGPR,
+ .offset_hplr = IMX6Q_SNVS_HPLR,
+ .offset_lplr = IMX6Q_SNVS_LPLR,
+};
+
+static int snvs_lpgpr_write(void *context, unsigned int offset, void *val,
+ size_t bytes)
+{
+ struct snvs_lpgpr_priv *priv = context;
+ const struct snvs_lpgpr_cfg *dcfg = priv->dcfg;
+ unsigned int lock_reg;
+ int ret;
+
+ ret = regmap_read(priv->regmap, dcfg->offset_hplr, &lock_reg);
+ if (ret < 0)
+ return ret;
+
+ if (lock_reg & IMX6Q_GPR_SL)
+ return -EPERM;
+
+ ret = regmap_read(priv->regmap, dcfg->offset_lplr, &lock_reg);
+ if (ret < 0)
+ return ret;
+
+ if (lock_reg & IMX6Q_GPR_HL)
+ return -EPERM;
+
+ return regmap_bulk_write(priv->regmap, dcfg->offset + offset, val,
+ bytes / 4);
+}
+
+static int snvs_lpgpr_read(void *context, unsigned int offset, void *val,
+ size_t bytes)
+{
+ struct snvs_lpgpr_priv *priv = context;
+ const struct snvs_lpgpr_cfg *dcfg = priv->dcfg;
+
+ return regmap_bulk_read(priv->regmap, dcfg->offset + offset,
+ val, bytes / 4);
+}
+
+static int snvs_lpgpr_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct device_node *node = dev->of_node;
+ struct device_node *syscon_node;
+ struct snvs_lpgpr_priv *priv;
+ struct nvmem_config *cfg;
+ struct nvmem_device *nvmem;
+ const struct snvs_lpgpr_cfg *dcfg;
+
+ if (!node)
+ return -ENOENT;
+
+ priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ dcfg = of_device_get_match_data(dev);
+ if (!dcfg)
+ return -EINVAL;
+
+ syscon_node = of_get_parent(node);
+ if (!syscon_node)
+ return -ENODEV;
+
+ priv->regmap = syscon_node_to_regmap(syscon_node);
+ of_node_put(syscon_node);
+ if (IS_ERR(priv->regmap))
+ return PTR_ERR(priv->regmap);
+
+ priv->dcfg = dcfg;
+
+ cfg = &priv->cfg;
+ cfg->priv = priv;
+ cfg->name = dev_name(dev);
+ cfg->dev = dev;
+ cfg->stride = 4,
+ cfg->word_size = 4,
+ cfg->size = 4,
+ cfg->owner = THIS_MODULE,
+ cfg->reg_read = snvs_lpgpr_read,
+ cfg->reg_write = snvs_lpgpr_write,
+
+ nvmem = nvmem_register(cfg);
+ if (IS_ERR(nvmem))
+ return PTR_ERR(nvmem);
+
+ platform_set_drvdata(pdev, nvmem);
+
+ return 0;
+}
+
+static int snvs_lpgpr_remove(struct platform_device *pdev)
+{
+ struct nvmem_device *nvmem = platform_get_drvdata(pdev);
+
+ return nvmem_unregister(nvmem);
+}
+
+static const struct of_device_id snvs_lpgpr_dt_ids[] = {
+ { .compatible = "fsl,imx6q-snvs-lpgpr", .data = &snvs_lpgpr_cfg_imx6q },
+ { .compatible = "fsl,imx6ul-snvs-lpgpr",
+ .data = &snvs_lpgpr_cfg_imx6q },
+ { },
+};
+MODULE_DEVICE_TABLE(of, snvs_lpgpr_dt_ids);
+
+static struct platform_driver snvs_lpgpr_driver = {
+ .probe = snvs_lpgpr_probe,
+ .remove = snvs_lpgpr_remove,
+ .driver = {
+ .name = "snvs_lpgpr",
+ .of_match_table = snvs_lpgpr_dt_ids,
+ },
+};
+module_platform_driver(snvs_lpgpr_driver);
+
+MODULE_AUTHOR("Oleksij Rempel <o.rempel@pengutronix.de>");
+MODULE_DESCRIPTION("Low Power General Purpose Register in i.MX6 Secure Non-Volatile Storage");
+MODULE_LICENSE("GPL v2");
--
2.11.0
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