nuvoton: battery-backed ram

Add bindings and entry for the battery-backed ram in the nuvoton
npcx. This commit is an upstream port of
https://source.chromium.org/chromiumos/chromiumos/codesearch/+/main:src/platform/ec/zephyr/dts/bindings/cros_bbram/nuvoton,npcx-cros-bbram.yaml;l=1;drc=e9af813c36b7b411bf2a01cbc1b09d5fdec49b8a

Along with a bit of cleaning up and an emulator.

Signed-off-by: Yuval Peress <peress@chromium.org>

include/drivers/bbram.h

@@ -0,0 +1,228 @@
+/*
+ * Copyright (c) 2021 Google Inc
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef ZEPHYR_INCLUDE_DRIVERS_BBRAM_H
+#define ZEPHYR_INCLUDE_DRIVERS_BBRAM_H
+
+#include <device.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * API template to check if the BBRAM is invalid.
+ *
+ * @see bbram_check_invlaid
+ */
+typedef int (*bbram_api_check_invalid)(const struct device *dev);
+
+/**
+ * API template to check for standby power failure.
+ *
+ * @see bbram_check_standby_power
+ */
+typedef int (*bbram_api_check_standby_power)(const struct device *dev);
+
+/**
+ * API template to check for V CC1 power failure.
+ *
+ * @see bbram_check_power
+ */
+typedef int (*bbram_api_check_power)(const struct device *dev);
+
+/**
+ * API template to check the size of the BBRAM
+ *
+ * @see bbram_get_size
+ */
+typedef int (*bbram_api_get_size)(const struct device *dev, size_t *size);
+
+/**
+ * API template to read from BBRAM.
+ *
+ * @see bbram_read
+ */
+typedef int (*bbram_api_read)(const struct device *dev, size_t offset, size_t size,
+			      uint8_t *data);
+
+/**
+ * API template to write to BBRAM.
+ *
+ * @see bbram_write
+ */
+typedef int (*bbram_api_write)(const struct device *dev, size_t offset, size_t size,
+			       const uint8_t *data);
+
+__subsystem struct bbram_driver_api {
+	bbram_api_check_invalid check_invalid;
+	bbram_api_check_standby_power check_standby_power;
+	bbram_api_check_power check_power;
+	bbram_api_get_size get_size;
+	bbram_api_read read;
+	bbram_api_write write;
+};
+
+/**
+ * @brief Check if BBRAM is invalid
+ *
+ * Check if "Invalid Battery-Backed RAM" status is set then reset the status
+ * bit. This may occur as a result to low voltage at the VBAT pin.
+ *
+ * @param dev BBRAM device pointer.
+ * @return 0 if the Battery-Backed RAM data is valid, -EFAULT otherwise.
+ */
+__syscall int bbram_check_invalid(const struct device *dev);
+
+static inline int z_impl_bbram_check_invalid(const struct device *dev)
+{
+	const struct bbram_driver_api *api =
+		(const struct bbram_driver_api *)dev->api;
+
+	if (!api->check_invalid) {
+		return -ENOTSUP;
+	}
+
+	return api->check_invalid(dev);
+}
+
+/**
+ * @brief Check for standby (Volt SBY) power failure.
+ *
+ * Check if the V standby power domain is turned on after it was off then reset
+ * the status bit.
+ *
+ * @param dev BBRAM device pointer.
+ * @return 0 if V SBY power domain is in normal operation.
+ */
+__syscall int bbram_check_standby_power(const struct device *dev);
+
+static inline int z_impl_bbram_check_standby_power(const struct device *dev)
+{
+	const struct bbram_driver_api *api =
+		(const struct bbram_driver_api *)dev->api;
+
+	if (!api->check_standby_power) {
+		return -ENOTSUP;
+	}
+
+	return api->check_standby_power(dev);
+}
+
+/**
+ * @brief Check for V CC1 power failure.
+ *
+ * This will return an error if the V CC1 power domain is turned on after it was
+ * off and reset the status bit.
+ *
+ * @param dev BBRAM device pointer.
+ * @return 0 if the V CC1 power domain is in normal operation, -EFAULT
+ * otherwise.
+ */
+__syscall int bbram_check_power(const struct device *dev);
+
+static inline int z_impl_bbram_check_power(const struct device *dev)
+{
+	const struct bbram_driver_api *api =
+		(const struct bbram_driver_api *)dev->api;
+
+	if (!api->check_power) {
+		return -ENOTSUP;
+	}
+
+	return api->check_power(dev);
+}
+
+/**
+ * Get the size of the BBRAM (in bytes).
+ *
+ * @param dev BBRAM device pointer.
+ * @param size Pointer to write the size to.
+ * @return 0 for success, -EFAULT otherwise.
+ */
+__syscall int bbram_get_size(const struct device *dev, size_t *size);
+
+static inline int z_impl_bbram_get_size(const struct device *dev, size_t *size)
+{
+	const struct bbram_driver_api *api =
+		(const struct bbram_driver_api *)dev->api;
+
+	if (!api->get_size) {
+		return -ENOTSUP;
+	}
+
+	return api->get_size(dev, size);
+}
+
+/**
+ * Read bytes from BBRAM.
+ *
+ * @param dev The BBRAM device pointer to read from.
+ * @param offset The offset into the RAM address to start reading from.
+ * @param size The number of bytes to read.
+ * @param data The buffer to load the data into.
+ * @return 0 on success, -EFAULT if the address range is out of bounds.
+ */
+__syscall int bbram_read(const struct device *dev, size_t offset, size_t size,
+			 uint8_t *data);
+
+static inline int z_impl_bbram_read(const struct device *dev, size_t offset,
+				    size_t size, uint8_t *data)
+{
+	const struct bbram_driver_api *api =
+		(const struct bbram_driver_api *)dev->api;
+
+	if (!api->read) {
+		return -ENOTSUP;
+	}
+
+	return api->read(dev, offset, size, data);
+}
+
+/**
+ * Write bytes to BBRAM.
+ *
+ * @param dev The BBRAM device pointer to write to.
+ * @param offset The offset into the RAM address to start writing to.
+ * @param size The number of bytes to write.
+ * @param data Pointer to the start of data to write.
+ * @return 0 on success, -EFAULT if the address range is out of bounds.
+ */
+__syscall int bbram_write(const struct device *dev, size_t offset, size_t size,
+			  const uint8_t *data);
+
+static inline int z_impl_bbram_write(const struct device *dev, size_t offset,
+				     size_t size, const uint8_t *data)
+{
+	const struct bbram_driver_api *api =
+		(const struct bbram_driver_api *)dev->api;
+
+	if (!api->write) {
+		return -ENOTSUP;
+	}
+
+	return api->write(dev, offset, size, data);
+}
+
+/**
+ *
+ * @param dev
+ * @param is_invalid
+ * @return
+ */
+int bbram_emul_set_invalid(const struct device *dev, bool is_invalid);
+
+int bbram_emul_set_standby_power_state(const struct device *dev, bool failure);
+
+int bbram_emul_set_power_state(const struct device *dev, bool failure);
+
+#ifdef __cplusplus
+}
+#endif
+
+#include <syscalls/bbram.h>
+
+#endif /* ZEPHYR_INCLUDE_DRIVERS_BBRAM_H */

include/sys/util.h

@@ -223,6 +223,22 @@ static inline int64_t arithmetic_shift_right(int64_t value, uint8_t shift)
 	return (value >> shift) | (sign_ext << (64 - shift));
 }
 
+/**
+ * @brief byte by byte memcpy.
+ *
+ * Copy `size` bytes of `src` into `dest`. This is guaranteed to be done byte by byte.
+ *
+ * @param dst Pointer to the destination memory.
+ * @param src Pointer to the source of the data.
+ * @param size The number of bytes to copy.
+ */
+static inline void bytecpy(void *dst, const void *src, size_t size)
+{
+	for (size_t i = 0; i < size; ++i) {
+		((uint8_t *)dst)[i] = ((uint8_t *)src)[i];
+	}
+}
+
 /**
  * @brief      Convert a single character into a hexadecimal nibble.
  *