Add new I2C backend

It is also possible to access the host processor via an I2C bus. This
proves to be both more reliable and quicker than bit-banging the FSI
bus so add this as a new backend and make it the default access
method.

Signed-off-by: Alistair Popple <alistair@popple.id.au>

1 files changed, 174 insertions, 0 deletions

diff --git a/libpdbg/i2c.c b/libpdbg/i2c.c
new file mode 100644
index 0000000..07a1dd1
--- /dev/null
+++ b/libpdbg/i2c.c
@@ -0,0 +1,174 @@
+/* Copyright 2016 IBM Corp.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * 	http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+ * implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <linux/i2c-dev.h>
+
+#include "bitutils.h"
+#include "operations.h"
+
+struct i2c_data {
+	int addr;
+	int fd;
+};
+
+static int i2c_set_addr(int fd, int addr)
+{
+	if (ioctl(fd, I2C_SLAVE, addr) < 0) {
+		PR_ERROR("Unable to set i2c slave address\n");
+		return -1;
+	}
+
+	return 0;
+}
+
+static int i2c_getcfam(struct scom_backend *backend, int processor_id,
+		       uint32_t *value, uint32_t addr)
+{
+	PR_ERROR("TODO: cfam access not supported with i2c backend\n");
+
+	return -1;
+}
+
+static int i2c_putcfam(struct scom_backend *backend, int processor_id,
+		       uint32_t value, uint32_t addr)
+{
+	PR_ERROR("TODO: cfam access not supported with i2c backend\n");
+
+	return -1;
+}
+
+static int i2c_set_scom_addr(struct i2c_data *i2c_data, uint32_t addr)
+{
+	uint8_t data[4];
+
+	addr <<= 1;
+	data[3] = GETFIELD(PPC_BITMASK32(0, 7), addr);
+	data[2] = GETFIELD(PPC_BITMASK32(8, 15), addr);
+	data[1] = GETFIELD(PPC_BITMASK32(16, 23), addr);
+	data[0] = GETFIELD(PPC_BITMASK32(23, 31), addr);
+	if (write(i2c_data->fd, data, sizeof(data)) != 4) {
+		PR_ERROR("Error writing address bytes\n");
+		return -1;
+	}
+
+	return 0;
+}
+
+static int i2c_getscom(struct scom_backend *backend, int processor_id,
+		       uint64_t *value, uint32_t addr)
+{
+	struct i2c_data *i2c_data = backend->priv;
+	uint8_t data[8];
+
+	if (processor_id) {
+		PR_ERROR("TODO: secondary processor access not supported with i2c backend\n");
+		return -1;
+	}
+
+	CHECK_ERR(i2c_set_scom_addr(i2c_data, addr));
+
+	if (read(i2c_data->fd, &data, sizeof(data)) != 8) {
+		PR_ERROR("Error reading data\n");
+		return -1;
+	}
+
+	*value = *((uint64_t *) data);
+
+	return 0;
+}
+
+static int i2c_putscom(struct scom_backend *backend, int processor_id,
+		       uint64_t value, uint32_t addr)
+{
+	struct i2c_data *i2c_data = backend->priv;
+	uint8_t data[12];
+
+	if (processor_id) {
+		PR_ERROR("TODO: secondary processor access not supported with i2c backend\n");
+		return -1;
+	}
+
+	/* Setup scom address */
+	addr <<= 1;
+	data[3] = GETFIELD(PPC_BITMASK32(0, 7), addr);
+	data[2] = GETFIELD(PPC_BITMASK32(8, 15), addr);
+	data[1] = GETFIELD(PPC_BITMASK32(16, 23), addr);
+	data[0] = GETFIELD(PPC_BITMASK32(23, 31), addr);
+
+	/* Add data value */
+	data[11] = GETFIELD(PPC_BITMASK(0, 7), value);
+	data[10] = GETFIELD(PPC_BITMASK(8, 15), value);
+	data[9] = GETFIELD(PPC_BITMASK(16, 23), value);
+	data[8] = GETFIELD(PPC_BITMASK(23, 31), value);
+	data[7] = GETFIELD(PPC_BITMASK(32, 39), value);
+	data[6] = GETFIELD(PPC_BITMASK(40, 47), value);
+	data[5] = GETFIELD(PPC_BITMASK(48, 55), value);
+	data[4] = GETFIELD(PPC_BITMASK(56, 63), value);
+
+	/* Write value */
+	if (write(i2c_data->fd, data, sizeof(data)) != 12) {
+		PR_ERROR("Error writing data bytes\n");
+		return -1;
+	}
+
+	return 0;
+}
+
+static void i2c_destroy(struct scom_backend *backend)
+{
+	struct i2c_data *i2c_data = backend->priv;
+
+	close(i2c_data->fd);
+	free(backend->priv);
+}
+
+/*
+ * Initialise a i2c backend on the given bus at the given bus address.
+ */
+struct scom_backend *i2c_init(char *bus, int addr)
+{
+	struct scom_backend *backend;
+	struct i2c_data *i2c_data;
+
+	backend = malloc(sizeof(*backend));
+	i2c_data = malloc(sizeof(*i2c_data));
+	if (!backend || !i2c_data)
+		exit(1);
+
+	i2c_data->addr = addr;
+	i2c_data->fd = open(bus, O_RDWR);
+	if (i2c_data->fd < 0) {
+		perror("Error opening bus");
+		exit(1);
+	}
+
+	if (i2c_set_addr(i2c_data->fd, addr) < 0)
+		exit(1);
+
+	backend->getscom = i2c_getscom;
+	backend->putscom = i2c_putscom;
+	backend->getcfam = i2c_getcfam;
+	backend->putcfam = i2c_putcfam;
+	backend->destroy = i2c_destroy;
+	backend->priv = i2c_data;
+
+	return backend;
+}