Add trivial driver which permits exposing syscon backed register
to userspace. This is useful e.g. to expose U-Boot boot counter
on various platforms where the boot counter is stored in random
volatile register, like STM32MP15xx TAMP_BKPxR register.
Signed-off-by: Marek Vasut <marex@xxxxxxx>
---
Cc: Alexandre Torgue <alexandre.torgue@xxxxxxxxxxx>
Cc: Rafał Miłecki <rafal@xxxxxxxxxx>
Cc: Rob Herring <robh+dt@xxxxxxxxxx>
Cc: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
Cc: devicetree@xxxxxxxxxxxxxxx
Cc: linux-stm32@xxxxxxxxxxxxxxxxxxxxxxxxxxxx
To: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
---
drivers/nvmem/Kconfig | 10 ++++
drivers/nvmem/Makefile | 2 +
drivers/nvmem/nvmem-syscon.c | 105 +++++++++++++++++++++++++++++++++++
3 files changed, 117 insertions(+)
create mode 100644 drivers/nvmem/nvmem-syscon.c
diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
index ec8a49c040031..cd9a7b00bc1ab 100644
--- a/drivers/nvmem/Kconfig
+++ b/drivers/nvmem/Kconfig
@@ -290,6 +290,16 @@ config NVMEM_SPRD_EFUSE
This driver can also be built as a module. If so, the module
will be called nvmem-sprd-efuse.
+config NVMEM_SYSCON
+ tristate "Generic syscon backed nvmem"
+ help
+ This is a driver for generic syscon backed nvmem. This can be
+ used to expose arbitrary syscon backed register to user space
+ via nvmem, like the U-Boot boot counter.
+
+ This driver can also be built as a module. If so, the module
+ will be called nvmem-syscon.
+
config NVMEM_STM32_ROMEM
tristate "STMicroelectronics STM32 factory-programmed memory support"
depends on ARCH_STM32 || COMPILE_TEST
diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
index fa80fe17e567e..6e170b30a1d1d 100644
--- a/drivers/nvmem/Makefile
+++ b/drivers/nvmem/Makefile
@@ -59,6 +59,8 @@ obj-$(CONFIG_NVMEM_SPMI_SDAM) += nvmem_qcom-spmi-sdam.o
nvmem_qcom-spmi-sdam-y += qcom-spmi-sdam.o
obj-$(CONFIG_NVMEM_SPRD_EFUSE) += nvmem_sprd_efuse.o
nvmem_sprd_efuse-y := sprd-efuse.o
+obj-$(CONFIG_NVMEM_SYSCON) += nvmem_syscon.o
+nvmem_syscon-y := nvmem-syscon.o
obj-$(CONFIG_NVMEM_STM32_ROMEM) += nvmem_stm32_romem.o
nvmem_stm32_romem-y := stm32-romem.o
obj-$(CONFIG_NVMEM_SUNPLUS_OCOTP) += nvmem_sunplus_ocotp.o
diff --git a/drivers/nvmem/nvmem-syscon.c b/drivers/nvmem/nvmem-syscon.c
new file mode 100644
index 0000000000000..9a7f9a5e37609
--- /dev/null
+++ b/drivers/nvmem/nvmem-syscon.c
@@ -0,0 +1,105 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2022 Marek Vasut <marex@xxxxxxx>
+ *
+ * Based on snvs_lpgpr.c .
+ */
+
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/of_device.h>
+#include <linux/regmap.h>
+
+struct nvmem_syscon_priv {
+ struct device_d *dev;
+ struct regmap *regmap;
+ struct nvmem_config cfg;
+ unsigned int off;
+};
+
+static int nvmem_syscon_write(void *context, unsigned int offset, void *val,
+ size_t bytes)
+{
+ struct nvmem_syscon_priv *priv = context;
+
+ return regmap_bulk_write(priv->regmap, priv->off + offset,
+ val, bytes / 4);
+}
+
+static int nvmem_syscon_read(void *context, unsigned int offset, void *val,
+ size_t bytes)
+{
+ struct nvmem_syscon_priv *priv = context;
+
+ return regmap_bulk_read(priv->regmap, priv->off + offset,
+ val, bytes / 4);
+}
+
+static int nvmem_syscon_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct device_node *node = dev->of_node;
+ struct device_node *syscon_node;
+ struct nvmem_syscon_priv *priv;
+ struct nvmem_device *nvmem;
+ struct nvmem_config *cfg;
+ int ret;
+
+ if (!node)
+ return -ENOENT;
+
+ priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ ret = of_property_read_u32_index(node, "reg", 0, &priv->off);
+ if (ret)
+ return ret;
+
+ ret = of_property_read_u32_index(node, "reg", 1, &priv->cfg.size);
+ if (ret)
+ return ret;
+
+ 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);
+
+ cfg = &priv->cfg;
+ cfg->priv = priv;
+ cfg->name = dev_name(dev);
+ cfg->dev = dev;
+ cfg->stride = 4;
+ cfg->word_size = 4;
+ cfg->owner = THIS_MODULE;
+ cfg->reg_read = nvmem_syscon_read;
+ cfg->reg_write = nvmem_syscon_write;
+
+ nvmem = devm_nvmem_register(dev, cfg);
+
+ return PTR_ERR_OR_ZERO(nvmem);
+}
+
+static const struct of_device_id nvmem_syscon_dt_ids[] = {
+ { .compatible = "nvmem-syscon" },
+ { },
+};
+MODULE_DEVICE_TABLE(of, nvmem_syscon_dt_ids);
+
+static struct platform_driver nvmem_syscon_driver = {
+ .probe = nvmem_syscon_probe,
+ .driver = {
+ .name = "nvmem-syscon",
+ .of_match_table = nvmem_syscon_dt_ids,
+ },
+};
+module_platform_driver(nvmem_syscon_driver);
+
+MODULE_AUTHOR("Marek Vasut <marex@xxxxxxx>");
+MODULE_DESCRIPTION("Generic syscon nvmem driver");
+MODULE_LICENSE("GPL");
--
2.35.1
