Message-Id: <1473799071-12830-1-git-send-email-vadimp@mellanox.com>
Date:   Tue, 13 Sep 2016 20:37:51 +0000
From:   vadimp@...lanox.com
To:     wsa@...-dreams.de, peda@...ntia.se
Cc:     linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        jiri@...nulli.us, Vadim Pasternak <vadimp@...lanox.com>,
        Michael Shych <michaelsh@...lanox.com>
Subject: [patch v5] i2c: mux: mellanox: add driver

From: Vadim Pasternak <vadimp@...lanox.com>

This driver allows I2C routing controlled through CPLD select registers on
a wide range of Mellanox systems (CPLD Lattice device).
MUX selection is provided by digital and analog HW. Analog part is not
under SW control.
Digital part is under CPLD control (channel selection/de-selection).

Connectivity schema.
i2c-mlxcpld                                 Digital               Analog
driver
*--------*                                 * -> mux1 (virt bus2) -> mux ->|
| I2CLPC | i2c physical                    * -> mux2 (virt bus3) -> mux ->|
| bridge | bus 1                 *---------*                              |
| logic  |---------------------> * mux reg *                              |
| in CPLD|                       *---------*                              |
*--------*   i2c-mux-mlxpcld          ^    * -> muxn (virt busn) -> mux ->|
    |        driver                   |                                   |
    |        *---------------*        |                             Devices
    |        * CPLD (i2c bus)* select |
    |        * registers for *--------*
    |        * mux selection * deselect
    |        *---------------*
    |                 |
<-------->     <----------->
i2c cntrl      Board cntrl reg
reg space      space (mux select,
               IO, LED, WD, info)

i2c-mux-mlxpcld does not necessarily require i2c-mlxcpld. It can be used
along with another bus driver, and still control i2c routing through CPLD
mux selection, in case the system is equipped with CPLD capable of mux
selection control.

The Kconfig currently controlling compilation of this code is:
drivers/i2c/muxes/Kconfig:config I2C_MUX_MLXCPLD

Signed-off-by: Michael Shych <michaelsh@...lanox.com>
Signed-off-by: Vadim Pasternak <vadimp@...lanox.com>
Reviewed-by: Jiri Pirko <jiri@...lanox.com>
---
v4->v5
 Fixes issues pointed out by Peter:
  - Fix text is submit message;
  - Fix text in Kconfig;
  - Arrange Makefile in alphabetic order;
  - Fix several comments;
  - Drop assignment for force to zero in probe;
  - Remove error message in probe - error message from i2c_mux_add_adapter
    is sufficient;
v3->v4
 Fixes issues pointed out by Peter:
  - Remove mlxcpld_mux_type;
  - Remove member type from mux control structure;
  - Remove variable muxes;
  - mlxcpld_mux_reg_write - set address from client;
  - mlxcpld_mux_reg_write - try smbus_xfer
  - mlxcpld_mux_select_chan - remove compare with for mux type;
  - mlxcpld_mux_probe - use I2C_FUNC_SMBUS_WRITE_BYTE_DATA instead of
    I2C_FUNC_SMBUS_BYTE
  - mlxcpld_mux_probe - remove switch statement
  - mlxcpld_mux_probe - update comment;
  - mlxcpld_mux_probe -change logic in testing num_adaps;
  - remove members first_channel and addr from mlxcpld_mux_plat_data
    structure;
v2->v3
 Fixes issues pointed out by Peter:
  - Fix several comments;
  - In MAINTAINERS file use linux-i2c instead of linux-kernel;
  - Place include files in alphabetic order;
  - When channel select fail, set last_chan to zero for cleaning last value;
  - Return with error from probe if there is no platform data;
  - Use i2c_mux_reg driver for the lpc_access cases:
    it fit well for Mellanox system with LPC access - has been tested and it
	works good.
  - Limit this driver to i2c_access only one device (mlxcpld_mux_module).
v1->v2
 Fixes issues pointed out by Peter:
  - changes in commit cover massage;
  - change leg to channel in comments;
  - missed return err;
  - use platform data mux array rather the offset from 1st channel in probe
    routine;
  - remove owner field from driver structure;
  - use module_i2c_driver macros, instead if __init and __exit;
  - remove deselect on exit flag;
  - add record to MAINTAINER file;
---
 MAINTAINERS                         |   8 ++
 drivers/i2c/muxes/Kconfig           |  11 ++
 drivers/i2c/muxes/Makefile          |   1 +
 drivers/i2c/muxes/i2c-mux-mlxcpld.c | 220 ++++++++++++++++++++++++++++++++++++
 include/linux/i2c/mlxcpld.h         |  52 +++++++++
 5 files changed, 292 insertions(+)
 create mode 100644 drivers/i2c/muxes/i2c-mux-mlxcpld.c
 create mode 100644 include/linux/i2c/mlxcpld.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 0bbe4b1..be83d69 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7655,6 +7655,14 @@ W:	http://www.mellanox.com
 Q:	http://patchwork.ozlabs.org/project/netdev/list/
 F:	drivers/net/ethernet/mellanox/mlxsw/
 
+MELLANOX MLXCPLD I2C MUX DRIVER
+M:	Vadim Pasternak <vadimp@...lanox.com>
+M:	Michael Shych <michaelsh@...lanox.com>
+L:	linux-i2c@...r.kernel.org
+S:	Supported
+W:	http://www.mellanox.com
+F:	drivers/i2c/muxes/i2c-mux-mlxcpld.c
+
 SOFT-ROCE DRIVER (rxe)
 M:	Moni Shoua <monis@...lanox.com>
 L:	linux-rdma@...r.kernel.org
diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
index e280c8e..d033402 100644
--- a/drivers/i2c/muxes/Kconfig
+++ b/drivers/i2c/muxes/Kconfig
@@ -81,4 +81,15 @@ config I2C_DEMUX_PINCTRL
 	  demultiplexer that uses the pinctrl subsystem. This is useful if you
 	  want to change the I2C master at run-time depending on features.
 
+config I2C_MUX_MLXCPLD
+        tristate "Mellanox CPLD based I2C multiplexer"
+        help
+          If you say yes to this option, support will be included for a
+          CPLD based I2C multiplexer. This driver provides access to
+          I2C busses connected through a MUX, which is controlled
+          by a CPLD register.
+
+          This driver can also be built as a module.  If so, the module
+          will be called i2c-mux-mlxcpld.
+
 endmenu
diff --git a/drivers/i2c/muxes/Makefile b/drivers/i2c/muxes/Makefile
index 7c267c2..9948fa4 100644
--- a/drivers/i2c/muxes/Makefile
+++ b/drivers/i2c/muxes/Makefile
@@ -6,6 +6,7 @@ obj-$(CONFIG_I2C_ARB_GPIO_CHALLENGE)	+= i2c-arb-gpio-challenge.o
 obj-$(CONFIG_I2C_DEMUX_PINCTRL)		+= i2c-demux-pinctrl.o
 
 obj-$(CONFIG_I2C_MUX_GPIO)	+= i2c-mux-gpio.o
+obj-$(CONFIG_I2C_MUX_MLXCPLD)	+= i2c-mux-mlxcpld.o
 obj-$(CONFIG_I2C_MUX_PCA9541)	+= i2c-mux-pca9541.o
 obj-$(CONFIG_I2C_MUX_PCA954x)	+= i2c-mux-pca954x.o
 obj-$(CONFIG_I2C_MUX_PINCTRL)	+= i2c-mux-pinctrl.o
diff --git a/drivers/i2c/muxes/i2c-mux-mlxcpld.c b/drivers/i2c/muxes/i2c-mux-mlxcpld.c
new file mode 100644
index 0000000..20be25a
--- /dev/null
+++ b/drivers/i2c/muxes/i2c-mux-mlxcpld.c
@@ -0,0 +1,220 @@
+/*
+ * drivers/i2c/muxes/i2c-mux-mlxcpld.c
+ * Copyright (c) 2016 Mellanox Technologies. All rights reserved.
+ * Copyright (c) 2016 Michael Shych <michaels@...lanox.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the names of the copyright holders nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * Alternatively, this software may be distributed under the terms of the
+ * GNU General Public License ("GPL") version 2 as published by the Free
+ * Software Foundation.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <linux/device.h>
+#include <linux/i2c.h>
+#include <linux/i2c-mux.h>
+#include <linux/io.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/version.h>
+#include <linux/i2c/mlxcpld.h>
+
+#define CPLD_MUX_MAX_NCHANS	8
+
+/* mlxcpld_mux - mux control structure:
+ * @last_chan - last register value
+ * @client - I2C device client
+ */
+struct mlxcpld_mux {
+	u8 last_chan;
+	struct i2c_client *client;
+};
+
+/* MUX logic description.
+ * Driver can support different mux control logic, according to CPLD
+ * implementation.
+ *
+ * Connectivity schema.
+ *
+ * i2c-mlxcpld                                 Digital               Analog
+ * driver
+ * *--------*                                 * -> mux1 (virt bus2) -> mux -> |
+ * | I2CLPC | i2c physical                    * -> mux2 (virt bus3) -> mux -> |
+ * | bridge | bus 1                 *---------*                               |
+ * | logic  |---------------------> * mux reg *                               |
+ * | in CPLD|                       *---------*                               |
+ * *--------*   i2c-mux-mlxpcld          ^    * -> muxn (virt busn) -> mux -> |
+ *     |        driver                   |                                    |
+ *     |        *---------------*        |                              Devices
+ *     |        * CPLD (i2c bus)* select |
+ *     |        * registers for *--------*
+ *     |        * mux selection * deselect
+ *     |        *---------------*
+ *     |                 |
+ * <-------->     <----------->
+ * i2c cntrl      Board cntrl reg
+ * reg space      space (mux select,
+ *                IO, LED, WD, info)
+ *
+ */
+
+static const struct i2c_device_id mlxcpld_mux_id[] = {
+	{ "mlxcpld_mux_module", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, mlxcpld_mux_id);
+
+/* Write to mux register. Don't use i2c_transfer() and i2c_smbus_xfer()
+ * for this as they will try to lock adapter a second time.
+ */
+static int mlxcpld_mux_reg_write(struct i2c_adapter *adap,
+				 struct i2c_client *client, u8 val)
+{
+	struct mlxcpld_mux_plat_data *pdata = dev_get_platdata(&client->dev);
+
+	if (adap->algo->master_xfer) {
+		struct i2c_msg msg;
+		u8 msgbuf[] = {pdata->sel_reg_addr, val};
+
+		msg.addr = client->addr;
+		msg.flags = 0;
+		msg.len = 2;
+		msg.buf = msgbuf;
+		return __i2c_transfer(adap, &msg, 1);
+	} else if (adap->algo->smbus_xfer) {
+		union i2c_smbus_data data;
+
+		data.byte = val;
+		return adap->algo->smbus_xfer(adap, client->addr,
+					      client->flags, I2C_SMBUS_WRITE,
+					      pdata->sel_reg_addr,
+					      I2C_SMBUS_BYTE_DATA, &data);
+	} else
+		return -ENODEV;
+}
+
+static int mlxcpld_mux_select_chan(struct i2c_mux_core *muxc, u32 chan)
+{
+	struct mlxcpld_mux *data = i2c_mux_priv(muxc);
+	struct i2c_client *client = data->client;
+	u8 regval = chan + 1;
+	int err = 0;
+
+	/* Only select the channel if its different from the last channel */
+	if (data->last_chan != regval) {
+		err = mlxcpld_mux_reg_write(muxc->parent, client, regval);
+		if (err)
+			data->last_chan = 0;
+		else
+			data->last_chan = regval;
+	}
+
+	return err;
+}
+
+static int mlxcpld_mux_deselect(struct i2c_mux_core *muxc, u32 chan)
+{
+	struct mlxcpld_mux *data = i2c_mux_priv(muxc);
+	struct i2c_client *client = data->client;
+
+	/* Deselect active channel */
+	data->last_chan = 0;
+
+	return mlxcpld_mux_reg_write(muxc->parent, client, data->last_chan);
+}
+
+/* Probe/reomove functions */
+static int mlxcpld_mux_probe(struct i2c_client *client,
+			     const struct i2c_device_id *id)
+{
+	struct i2c_adapter *adap = to_i2c_adapter(client->dev.parent);
+	struct mlxcpld_mux_plat_data *pdata = dev_get_platdata(&client->dev);
+	struct i2c_mux_core *muxc;
+	int num, force;
+	struct mlxcpld_mux *data;
+	int err;
+
+	if (!pdata)
+		return -EINVAL;
+
+	if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_WRITE_BYTE_DATA))
+		return -ENODEV;
+
+	muxc = i2c_mux_alloc(adap, &client->dev, CPLD_MUX_MAX_NCHANS,
+			     sizeof(*data), 0, mlxcpld_mux_select_chan,
+			     mlxcpld_mux_deselect);
+	if (!muxc)
+		return -ENOMEM;
+
+	data = i2c_mux_priv(muxc);
+	i2c_set_clientdata(client, muxc);
+	data->client = client;
+	data->last_chan = 0; /* force the first selection */
+
+	/* Create an adapter for each channel. */
+	for (num = 0; num < CPLD_MUX_MAX_NCHANS; num++) {
+		if (num >= pdata->num_adaps)
+			/* discard unconfigured channels */
+			break;
+
+		force = pdata->adap_ids[num];
+
+		err = i2c_mux_add_adapter(muxc, force, num, 0);
+		if (err)
+			goto virt_reg_failed;
+	}
+
+	return 0;
+
+virt_reg_failed:
+	i2c_mux_del_adapters(muxc);
+	return err;
+}
+
+static int mlxcpld_mux_remove(struct i2c_client *client)
+{
+	struct i2c_mux_core *muxc = i2c_get_clientdata(client);
+
+	i2c_mux_del_adapters(muxc);
+	return 0;
+}
+
+static struct i2c_driver mlxcpld_mux_driver = {
+	.driver		= {
+		.name	= "mlxcpld-mux",
+	},
+	.probe		= mlxcpld_mux_probe,
+	.remove		= mlxcpld_mux_remove,
+	.id_table	= mlxcpld_mux_id,
+};
+
+module_i2c_driver(mlxcpld_mux_driver);
+
+MODULE_AUTHOR("Michael Shych (michaels@...lanox.com)");
+MODULE_DESCRIPTION("Mellanox I2C-CPLD-MUX driver");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:i2c-mux-mlxcpld");
diff --git a/include/linux/i2c/mlxcpld.h b/include/linux/i2c/mlxcpld.h
new file mode 100644
index 0000000..b08dcb1
--- /dev/null
+++ b/include/linux/i2c/mlxcpld.h
@@ -0,0 +1,52 @@
+/*
+ * mlxcpld.h - Mellanox I2C multiplexer support in CPLD
+ *
+ * Copyright (c) 2016 Mellanox Technologies. All rights reserved.
+ * Copyright (c) 2016 Michael Shych <michaels@...lanox.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the names of the copyright holders nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * Alternatively, this software may be distributed under the terms of the
+ * GNU General Public License ("GPL") version 2 as published by the Free
+ * Software Foundation.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _LINUX_I2C_MLXCPLD_H
+#define _LINUX_I2C_MLXCPLD_H
+
+/* Platform data for the CPLD I2C multiplexers */
+
+/* mlxcpld_mux_plat_data - per mux data, used with i2c_register_board_info
+ * @adap_ids - adapter array
+ * @num_adaps - number of adapters
+ * @sel_reg_addr - mux select register offset in CPLD space
+ */
+struct mlxcpld_mux_plat_data {
+	int *adap_ids;
+	int num_adaps;
+	int sel_reg_addr;
+};
+
+#endif /* _LINUX_I2C_MLXCPLD_H */
-- 
2.1.4

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