soc: at91: Add Atmel SFR SN (Serial Number) support

Add support to read SFR's read-only registers providing the SoC
Serial Numbers (SN0+SN1) to userspace.

~ #  hexdump -n 8  -e'"%d\n"' /sys/bus/nvmem/devices/atmel-sfr0/nvmem
959527243
371539274

Signed-off-by: Kamel Bouhara <kamel.bouhara@bootlin.com>
Tested-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20191004151802.21793-1-kamel.bouhara@bootlin.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

diff --git a/drivers/soc/atmel/Kconfig b/drivers/soc/atmel/Kconfig
index 0552813..50caf6d 100644 (file)
--- a/drivers/soc/atmel/Kconfig
+++ b/drivers/soc/atmel/Kconfig
@@ -5,3 +5,14 @@ config AT91_SOC_ID
        default ARCH_AT91
        help
          Include support for the SoC bus on the Atmel ARM SoCs.
+
+config AT91_SOC_SFR
+       tristate "Special Function Registers support"
+       depends on ARCH_AT91 || COMPILE_TEST
+       help
+         This is a driver for the Special Function Registers available on
+         Atmel SAMA5Dx SoCs, providing access to specific aspects of the
+         integrated memory, bridge implementations, processor etc.
+
+         This driver can also be built as a module. If so, the module
+         will be called sfr.

diff --git a/drivers/soc/atmel/Makefile b/drivers/soc/atmel/Makefile
index 7ca355d..d849a89 100644 (file)
--- a/drivers/soc/atmel/Makefile
+++ b/drivers/soc/atmel/Makefile
@@ -1,2 +1,3 @@
 # SPDX-License-Identifier: GPL-2.0-only
 obj-$(CONFIG_AT91_SOC_ID) += soc.o
+obj-$(CONFIG_AT91_SOC_SFR) += sfr.o

diff --git a/drivers/soc/atmel/sfr.c b/drivers/soc/atmel/sfr.c
new file mode 100644 (file)
index 0000000..0525eef
--- /dev/null
+++ b/drivers/soc/atmel/sfr.c
@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * sfr.c - driver for special function registers
+ *
+ * Copyright (C) 2019 Bootlin.
+ *
+ */
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/random.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#define SFR_SN0                0x4c
+#define SFR_SN_SIZE    8
+
+struct atmel_sfr_priv {
+       struct regmap                   *regmap;
+};
+
+static int atmel_sfr_read(void *context, unsigned int offset,
+                         void *buf, size_t bytes)
+{
+       struct atmel_sfr_priv *priv = context;
+
+       return regmap_bulk_read(priv->regmap, SFR_SN0 + offset,
+                               buf, bytes / 4);
+}
+
+static struct nvmem_config atmel_sfr_nvmem_config = {
+       .name = "atmel-sfr",
+       .read_only = true,
+       .word_size = 4,
+       .stride = 4,
+       .size = SFR_SN_SIZE,
+       .reg_read = atmel_sfr_read,
+};
+
+static int atmel_sfr_probe(struct platform_device *pdev)
+{
+       struct device *dev = &pdev->dev;
+       struct device_node *np = dev->of_node;
+       struct nvmem_device *nvmem;
+       struct atmel_sfr_priv *priv;
+       u8 sn[SFR_SN_SIZE];
+       int ret;
+
+       priv = devm_kmalloc(dev, sizeof(*priv), GFP_KERNEL);
+       if (!priv)
+               return -ENOMEM;
+
+       priv->regmap = syscon_node_to_regmap(np);
+       if (IS_ERR(priv->regmap)) {
+               dev_err(dev, "cannot get parent's regmap\n");
+               return PTR_ERR(priv->regmap);
+       }
+
+       atmel_sfr_nvmem_config.dev = dev;
+       atmel_sfr_nvmem_config.priv = priv;
+
+       nvmem = devm_nvmem_register(dev, &atmel_sfr_nvmem_config);
+       if (IS_ERR(nvmem)) {
+               dev_err(dev, "error registering nvmem config\n");
+               return PTR_ERR(nvmem);
+       }
+
+       ret = atmel_sfr_read(priv, 0, sn, SFR_SN_SIZE);
+       if (ret == 0)
+               add_device_randomness(sn, SFR_SN_SIZE);
+
+       return ret;
+}
+
+static const struct of_device_id atmel_sfr_dt_ids[] = {
+       {
+               .compatible = "atmel,sama5d2-sfr",
+       }, {
+               .compatible = "atmel,sama5d4-sfr",
+       }, {
+               /* sentinel */
+       },
+};
+MODULE_DEVICE_TABLE(of, atmel_sfr_dt_ids);
+
+static struct platform_driver atmel_sfr_driver = {
+       .probe = atmel_sfr_probe,
+       .driver = {
+               .name = "atmel-sfr",
+               .of_match_table = atmel_sfr_dt_ids,
+       },
+};
+module_platform_driver(atmel_sfr_driver);
+
+MODULE_AUTHOR("Kamel Bouhara <kamel.bouhara@bootlin.com>");
+MODULE_DESCRIPTION("Atmel SFR SN driver for SAMA5D2/4 SoC family");
+MODULE_LICENSE("GPL v2");