core: arm: rpc i2c trampoline driver

Gives OP-TEE access to the i2c buses initialized and controlled by the
REE kernel. This is done by memory mapping a buffer from the thread's
cache where the input or output data is transferred.

Using this mechanism, OP-TEE clients do not have to worry about REE
RUNTIME_PM features switching off clocks from the controllers or
collisions with other bus masters.

This driver assumes that the I2C chip is on a REE statically assigned
bus which value is known to OP-TEE (it will not query/probe the REE).

The slave address can be either seven or ten bits. When using a ten
bit address, the corresponding flag needs to be set in the command and
the REE adapter must support the requested addressing mode.

Signed-off-by: Jorge Ramirez-Ortiz <jorge@foundries.io>
Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>
Reviewed-by: Etienne Carriere <etienne.carriere@linaro.org>

2 files changed, 62 insertions, 0 deletions

diff --git a/core/arch/arm/kernel/rpc_io_i2c.c b/core/arch/arm/kernel/rpc_io_i2c.c
new file mode 100644
index 00000000..b48320ad
--- /dev/null
+++ b/core/arch/arm/kernel/rpc_io_i2c.c
@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: BSD-2-Clause
+/*
+ * Copyright 2020 Foundries Ltd <jorge@foundries.io>
+ */
+#include <kernel/rpc_io_i2c.h>
+#include <kernel/thread.h>
+#include <mm/mobj.h>
+#include <string.h>
+
+/*
+ * @brief: I2C master transfer request to an I2C slave device.
+ * It is the responsibility of the caller to validate the number of bytes
+ * processed by the REE.
+ *
+ * @param req: the secure world I2C master request
+ * @param len: the number of bytes processed by REE
+ * @returns: TEE_SUCCESS on success, TEE_ERROR_XXX on error.
+ */
+TEE_Result rpc_io_i2c_transfer(struct rpc_i2c_request *req, size_t *len)
+{
+	struct thread_param p[4] = { };
+	TEE_Result res = TEE_SUCCESS;
+	struct mobj *mobj = NULL;
+	uint8_t *va = NULL;
+
+	assert(req);
+
+	if (!len)
+		return TEE_ERROR_BAD_PARAMETERS;
+
+	va = thread_rpc_shm_cache_alloc(THREAD_SHM_TYPE_KERNEL_PRIVATE,
+					req->buffer_len, &mobj);
+	if (!va)
+		return TEE_ERROR_OUT_OF_MEMORY;
+
+	if (req->mode == RPC_I2C_MODE_WRITE)
+		memcpy(va, req->buffer, req->buffer_len);
+
+	p[0] = THREAD_PARAM_VALUE(IN, req->mode, req->bus, req->chip);
+	p[1] = THREAD_PARAM_VALUE(IN, req->flags, 0, 0);
+	p[2] = THREAD_PARAM_MEMREF(INOUT, mobj, 0, req->buffer_len);
+	p[3] = THREAD_PARAM_VALUE(OUT, 0, 0, 0);
+
+	res = thread_rpc_cmd(OPTEE_RPC_CMD_I2C_TRANSFER, ARRAY_SIZE(p), p);
+	if (res != TEE_SUCCESS)
+		return res;
+
+	/*
+	 * Reporting more bytes than supplied or requested from the I2C chip is
+	 * an REE error
+	 */
+	if (p[2].u.value.a > req->buffer_len)
+		return TEE_ERROR_EXCESS_DATA;
+
+	*len = p[2].u.value.a;
+
+	if (req->mode == RPC_I2C_MODE_READ)
+		memcpy(req->buffer, va, *len);
+
+	return TEE_SUCCESS;
+}
diff --git a/core/arch/arm/kernel/sub.mk b/core/arch/arm/kernel/sub.mk
index 4190a0c5..71a89553 100644
--- a/core/arch/arm/kernel/sub.mk
+++ b/core/arch/arm/kernel/sub.mk
@@ -6,6 +6,7 @@ srcs-$(CFG_SECSTOR_TA) += secstor_ta.c
 endif
 srcs-y += pseudo_ta.c
 srcs-y += tee_time.c
+srcs-y += rpc_io_i2c.c
 srcs-y += otp_stubs.c
 srcs-y += delay.c