i2c: Add Tegra BPMP I2C proxy driver

Add Tegra BPMP I2C driver. The BPMP is the boot and power management
processor embedded in Tegra SoCs. In newer SoC versions, access to one
of the I2C busses goes via the BPMP, requiring a different "proxy" I2C
driver that accesses the bus via the real I2C driver embedded in the
BPMP firmware.
Signed-off-by: Shardar Shariff Md <smohammed@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

drivers/i2c/busses/Kconfig

@@ -930,6 +930,17 @@ config I2C_TEGRA
 	  If you say yes to this option, support will be included for the
 	  I2C controller embedded in NVIDIA Tegra SOCs
 
+config I2C_TEGRA_BPMP
+	tristate "NVIDIA Tegra BPMP I2C controller"
+	depends on TEGRA_BPMP
+	help
+	  If you say yes to this option, support will be included for the I2C
+	  controller embedded in NVIDIA Tegra SoCs accessed via the BPMP.
+
+	  This I2C driver is a 'virtual' I2C driver. The real driver is part
+	  of the BPMP firmware, and this driver merely communicates with that
+	  real driver.
+
 config I2C_UNIPHIER
 	tristate "UniPhier FIFO-less I2C controller"
 	depends on ARCH_UNIPHIER || COMPILE_TEST

drivers/i2c/busses/Makefile

@@ -89,6 +89,7 @@ obj-$(CONFIG_I2C_STM32F4)	+= i2c-stm32f4.o
 obj-$(CONFIG_I2C_STU300)	+= i2c-stu300.o
 obj-$(CONFIG_I2C_SUN6I_P2WI)	+= i2c-sun6i-p2wi.o
 obj-$(CONFIG_I2C_TEGRA)		+= i2c-tegra.o
+obj-$(CONFIG_I2C_TEGRA_BPMP)	+= i2c-tegra-bpmp.o
 obj-$(CONFIG_I2C_UNIPHIER)	+= i2c-uniphier.o
 obj-$(CONFIG_I2C_UNIPHIER_F)	+= i2c-uniphier-f.o
 obj-$(CONFIG_I2C_VERSATILE)	+= i2c-versatile.o

drivers/i2c/busses/i2c-tegra-bpmp.c

+/*
+ * drivers/i2c/busses/i2c-tegra-bpmp.c
+ *
+ * Copyright (c) 2016 NVIDIA Corporation.  All rights reserved.
+ *
+ * Author: Shardar Shariff Md <smohammed@nvidia.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+
+#include <soc/tegra/bpmp-abi.h>
+#include <soc/tegra/bpmp.h>
+
+/*
+ * Serialized I2C message header size is 6 bytes and includes address, flags
+ * and length
+ */
+#define SERIALI2C_HDR_SIZE 6
+
+struct tegra_bpmp_i2c {
+	struct i2c_adapter adapter;
+	struct device *dev;
+
+	struct tegra_bpmp *bpmp;
+	unsigned int bus;
+};
+
+/*
+ * Linux flags are translated to BPMP defined I2C flags that are used in BPMP
+ * firmware I2C driver to avoid any issues in future if Linux I2C flags are
+ * changed.
+ */
+static int tegra_bpmp_xlate_flags(u16 flags, u16 *out)
+{
+	if (flags & I2C_M_TEN) {
+		*out |= SERIALI2C_TEN;
+		flags &= ~I2C_M_TEN;
+	}
+
+	if (flags & I2C_M_RD) {
+		*out |= SERIALI2C_RD;
+		flags &= ~I2C_M_RD;
+	}
+
+	if (flags & I2C_M_STOP) {
+		*out |= SERIALI2C_STOP;
+		flags &= ~I2C_M_STOP;
+	}
+
+	if (flags & I2C_M_NOSTART) {
+		*out |= SERIALI2C_NOSTART;
+		flags &= ~I2C_M_NOSTART;
+	}
+
+	if (flags & I2C_M_REV_DIR_ADDR) {
+		*out |= SERIALI2C_REV_DIR_ADDR;
+		flags &= ~I2C_M_REV_DIR_ADDR;
+	}
+
+	if (flags & I2C_M_IGNORE_NAK) {
+		*out |= SERIALI2C_IGNORE_NAK;
+		flags &= ~I2C_M_IGNORE_NAK;
+	}
+
+	if (flags & I2C_M_NO_RD_ACK) {
+		*out |= SERIALI2C_NO_RD_ACK;
+		flags &= ~I2C_M_NO_RD_ACK;
+	}
+
+	if (flags & I2C_M_RECV_LEN) {
+		*out |= SERIALI2C_RECV_LEN;
+		flags &= ~I2C_M_RECV_LEN;
+	}
+
+	return (flags != 0) ? -EINVAL : 0;
+}
+
+/**
+ * The serialized I2C format is simply the following:
+ * [addr little-endian][flags little-endian][len little-endian][data if write]
+ * [addr little-endian][flags little-endian][len little-endian][data if write]
+ *  ...
+ *
+ * The flags are translated from Linux kernel representation to seriali2c
+ * representation. Any undefined flag being set causes an error.
+ *
+ * The data is there only for writes. Reads have the data transferred in the
+ * other direction, and thus data is not present.
+ *
+ * See deserialize_i2c documentation for the data format in the other direction.
+ */
+static int tegra_bpmp_serialize_i2c_msg(struct tegra_bpmp_i2c *i2c,
+					struct mrq_i2c_request *request,
+					struct i2c_msg *msgs,
+					unsigned int num)
+{
+	char *buf = request->xfer.data_buf;
+	unsigned int i, j, pos = 0;
+	int err;
+
+	for (i = 0; i < num; i++) {
+		struct i2c_msg *msg = &msgs[i];
+		u16 flags = 0;
+
+		err = tegra_bpmp_xlate_flags(msg->flags, &flags);
+		if (err < 0)
+			return err;
+
+		buf[pos++] = msg->addr & 0xff;
+		buf[pos++] = (msg->addr & 0xff00) >> 8;
+		buf[pos++] = flags & 0xff;
+		buf[pos++] = (flags & 0xff00) >> 8;
+		buf[pos++] = msg->len & 0xff;
+		buf[pos++] = (msg->len & 0xff00) >> 8;
+
+		if ((flags & SERIALI2C_RD) == 0) {
+			for (j = 0; j < msg->len; j++)
+				buf[pos++] = msg->buf[j];
+		}
+	}
+
+	request->xfer.data_size = pos;
+
+	return 0;
+}
+
+/**
+ * The data in the BPMP -> CPU direction is composed of sequential blocks for
+ * those messages that have I2C_M_RD. So, for example, if you have:
+ *
+ * - !I2C_M_RD, len == 5, data == a0 01 02 03 04
+ * - !I2C_M_RD, len == 1, data == a0
+ * - I2C_M_RD, len == 2, data == [uninitialized buffer 1]
+ * - !I2C_M_RD, len == 1, data == a2
+ * - I2C_M_RD, len == 2, data == [uninitialized buffer 2]
+ *
+ * ...then the data in the BPMP -> CPU direction would be 4 bytes total, and
+ * would contain 2 bytes that will go to uninitialized buffer 1, and 2 bytes
+ * that will go to uninitialized buffer 2.
+ */
+static int tegra_bpmp_i2c_deserialize(struct tegra_bpmp_i2c *i2c,
+				      struct mrq_i2c_response *response,
+				      struct i2c_msg *msgs,
+				      unsigned int num)
+{
+	size_t size = response->xfer.data_size, len = 0, pos = 0;
+	char *buf = response->xfer.data_buf;
+	unsigned int i;
+
+	for (i = 0; i < num; i++)
+		if (msgs[i].flags & I2C_M_RD)
+			len += msgs[i].len;
+
+	if (len != size)
+		return -EINVAL;
+
+	for (i = 0; i < num; i++) {
+		if (msgs[i].flags & I2C_M_RD) {
+			memcpy(msgs[i].buf, buf + pos, msgs[i].len);
+			pos += msgs[i].len;
+		}
+	}
+
+	return 0;
+}
+
+static int tegra_bpmp_i2c_msg_len_check(struct i2c_msg *msgs, unsigned int num)
+{
+	size_t tx_len = 0, rx_len = 0;
+	unsigned int i;
+
+	for (i = 0; i < num; i++)
+		if (!(msgs[i].flags & I2C_M_RD))
+			tx_len += SERIALI2C_HDR_SIZE + msgs[i].len;
+
+	if (tx_len > TEGRA_I2C_IPC_MAX_IN_BUF_SIZE)
+		return -EINVAL;
+
+	for (i = 0; i < num; i++)
+		if ((msgs[i].flags & I2C_M_RD))
+			rx_len += msgs[i].len;
+
+	if (rx_len > TEGRA_I2C_IPC_MAX_OUT_BUF_SIZE)
+		return -EINVAL;
+
+	return 0;
+}
+
+static int tegra_bpmp_i2c_msg_xfer(struct tegra_bpmp_i2c *i2c,
+				   struct mrq_i2c_request *request,
+				   struct mrq_i2c_response *response)
+{
+	struct tegra_bpmp_message msg;
+	int err;
+
+	request->cmd = CMD_I2C_XFER;
+	request->xfer.bus_id = i2c->bus;
+
+	memset(&msg, 0, sizeof(msg));
+	msg.mrq = MRQ_I2C;
+	msg.tx.data = request;
+	msg.tx.size = sizeof(*request);
+	msg.rx.data = response;
+	msg.rx.size = sizeof(*response);
+
+	if (irqs_disabled())
+		err = tegra_bpmp_transfer_atomic(i2c->bpmp, &msg);
+	else
+		err = tegra_bpmp_transfer(i2c->bpmp, &msg);
+
+	return err;
+}
+
+static int tegra_bpmp_i2c_xfer(struct i2c_adapter *adapter,
+			       struct i2c_msg *msgs, int num)
+{
+	struct tegra_bpmp_i2c *i2c = i2c_get_adapdata(adapter);
+	struct mrq_i2c_response response;
+	struct mrq_i2c_request request;
+	int err;
+
+	err = tegra_bpmp_i2c_msg_len_check(msgs, num);
+	if (err < 0) {
+		dev_err(i2c->dev, "unsupported message length\n");
+		return err;
+	}
+
+	memset(&request, 0, sizeof(request));
+	memset(&response, 0, sizeof(response));
+
+	err = tegra_bpmp_serialize_i2c_msg(i2c, &request, msgs, num);
+	if (err < 0) {
+		dev_err(i2c->dev, "failed to serialize message: %d\n", err);
+		return err;
+	}
+
+	err = tegra_bpmp_i2c_msg_xfer(i2c, &request, &response);
+	if (err < 0) {
+		dev_err(i2c->dev, "failed to transfer message: %d\n", err);
+		return err;
+	}
+
+	err = tegra_bpmp_i2c_deserialize(i2c, &response, msgs, num);
+	if (err < 0) {
+		dev_err(i2c->dev, "failed to deserialize message: %d\n", err);
+		return err;
+	}
+
+	return num;
+}
+
+static u32 tegra_bpmp_i2c_func(struct i2c_adapter *adapter)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_10BIT_ADDR |
+	       I2C_FUNC_PROTOCOL_MANGLING | I2C_FUNC_NOSTART;
+}
+
+static const struct i2c_algorithm tegra_bpmp_i2c_algo = {
+	.master_xfer = tegra_bpmp_i2c_xfer,
+	.functionality = tegra_bpmp_i2c_func,
+};
+
+static int tegra_bpmp_i2c_probe(struct platform_device *pdev)
+{
+	struct tegra_bpmp_i2c *i2c;
+	u32 value;
+	int err;
+
+	i2c = devm_kzalloc(&pdev->dev, sizeof(*i2c), GFP_KERNEL);
+	if (!i2c)
+		return -ENOMEM;
+
+	i2c->dev = &pdev->dev;
+
+	i2c->bpmp = dev_get_drvdata(pdev->dev.parent);
+	if (!i2c->bpmp)
+		return -ENODEV;
+
+	err = of_property_read_u32(pdev->dev.of_node, "nvidia,bpmp-bus-id",
+				   &value);
+	if (err < 0)
+		return err;
+
+	i2c->bus = value;
+
+	i2c_set_adapdata(&i2c->adapter, i2c);
+	i2c->adapter.owner = THIS_MODULE;
+	strlcpy(i2c->adapter.name, "Tegra BPMP I2C adapter",
+		sizeof(i2c->adapter.name));
+	i2c->adapter.algo = &tegra_bpmp_i2c_algo;
+	i2c->adapter.dev.parent = &pdev->dev;
+	i2c->adapter.dev.of_node = pdev->dev.of_node;
+
+	platform_set_drvdata(pdev, i2c);
+
+	return i2c_add_adapter(&i2c->adapter);
+}
+
+static int tegra_bpmp_i2c_remove(struct platform_device *pdev)
+{
+	struct tegra_bpmp_i2c *i2c = platform_get_drvdata(pdev);
+
+	i2c_del_adapter(&i2c->adapter);
+
+	return 0;
+}
+
+static const struct of_device_id tegra_bpmp_i2c_of_match[] = {
+	{ .compatible = "nvidia,tegra186-bpmp-i2c", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, tegra_bpmp_i2c_of_match);
+
+static struct platform_driver tegra_bpmp_i2c_driver = {
+	.driver = {
+		.name = "tegra-bpmp-i2c",
+		.of_match_table = tegra_bpmp_i2c_of_match,
+	},
+	.probe = tegra_bpmp_i2c_probe,
+	.remove = tegra_bpmp_i2c_remove,
+};
+module_platform_driver(tegra_bpmp_i2c_driver);
+
+MODULE_DESCRIPTION("NVIDIA Tegra BPMP I2C bus contoller driver");
+MODULE_AUTHOR("Shardar Shariff Md <smohammed@nvidia.com>");
+MODULE_AUTHOR("Juha-Matti Tilli");
+MODULE_LICENSE("GPL v2");