On 06.04.2017 10:39, Peter Rosin wrote:
Hi Michael,
I would still like to hear from someone with more gpio experience.
I'll ping Linus.
Anyway, from my point of view, there's just a few minor things left,
with comments inline as usual.
Thanks for you patience!
Thanks for review.
Cheers,
peda
On 2017-04-05 15:07, michael.hennerich@xxxxxxxxxx wrote:
From: Michael Hennerich <michael.hennerich@xxxxxxxxxx>
This patch adds support for the Analog Devices / Linear Technology
LTC4306 and LTC4305 4/2 Channel I2C Bus Multiplexer/Switches.
The LTC4306 optionally provides two general purpose input/output pins
(GPIOs) that can be configured as logic inputs, opendrain outputs or
push-pull outputs via the generic GPIOLIB framework.
Signed-off-by: Michael Hennerich <michael.hennerich@xxxxxxxxxx>
---
Changes since v1:
- Sort makefile entries
- Sort driver includes
- Use proper defines
- Miscellaneous coding style fixups
- Rename mux select callback
- Revise i2c-mux-idle-disconnect handling
- Add ENABLE GPIO handling on error and device removal.
- Remove surplus of_match_device call.
Changes since v2:
- Stop double error reporting (i2c_mux_add_adapter)
- Change subject
- Split dt bindings to separate patch
Changes since v3:
- Change subject and add spaces
- Convert to I2C_MUX_LOCKED
- Convert to regmap
- Remove local register cache
- Restore previous ENABLE GPIO handling
- Initially pulse ENABLE low
- Eliminate i2c client struct in driver state structure
- Simplify error return path
- Misc minor cleanups
---
MAINTAINERS | 8 +
drivers/i2c/muxes/Kconfig | 11 ++
drivers/i2c/muxes/Makefile | 1 +
drivers/i2c/muxes/i2c-mux-ltc4306.c | 310 ++++++++++++++++++++++++++++++++++++
4 files changed, 330 insertions(+)
create mode 100644 drivers/i2c/muxes/i2c-mux-ltc4306.c
diff --git a/MAINTAINERS b/MAINTAINERS
index c776906..9a27a19 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7698,6 +7698,14 @@ S: Maintained
F: Documentation/hwmon/ltc4261
F: drivers/hwmon/ltc4261.c
+LTC4306 I2C MULTIPLEXER DRIVER
+M: Michael Hennerich <michael.hennerich@xxxxxxxxxx>
+W: http://ez.analog.com/community/linux-device-drivers
+L: linux-i2c@xxxxxxxxxxxxxxx
+S: Supported
+F: drivers/i2c/muxes/i2c-mux-ltc4306.c
+F: Documentation/devicetree/bindings/i2c/i2c-mux-ltc4306.txt
+
LTP (Linux Test Project)
M: Mike Frysinger <vapier@xxxxxxxxxx>
M: Cyril Hrubis <chrubis@xxxxxxx>
diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
index 10b3d17..41153b4 100644
--- a/drivers/i2c/muxes/Kconfig
+++ b/drivers/i2c/muxes/Kconfig
@@ -30,6 +30,17 @@ config I2C_MUX_GPIO
This driver can also be built as a module. If so, the module
will be called i2c-mux-gpio.
+config I2C_MUX_LTC4306
+ tristate "LTC LTC4306/5 I2C multiplexer"
+ select GPIOLIB
+ select REGMAP_I2C
+ help
+ If you say yes here you get support for the LTC LTC4306 or LTC4305
This reads a bit funny, and I think you should just spell out the
first LTC? But perhaps not in the tristate above though, depending
on how long it gets?
Ok - I rename LTC -> Analog Devices
+ I2C mux/switch devices.
+
+ This driver can also be built as a module. If so, the module
+ will be called i2c-mux-ltc4306.
+
config I2C_MUX_PCA9541
tristate "NXP PCA9541 I2C Master Selector"
help
diff --git a/drivers/i2c/muxes/Makefile b/drivers/i2c/muxes/Makefile
index 9948fa4..ff7618c 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_LTC4306) += i2c-mux-ltc4306.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
diff --git a/drivers/i2c/muxes/i2c-mux-ltc4306.c b/drivers/i2c/muxes/i2c-mux-ltc4306.c
new file mode 100644
index 0000000..7d34434
--- /dev/null
+++ b/drivers/i2c/muxes/i2c-mux-ltc4306.c
@@ -0,0 +1,310 @@
+/*
+ * Linear Technology LTC4306 and LTC4305 I2C multiplexer/switch
+ *
+ * Copyright (C) 2017 Analog Devices Inc.
+ *
+ * Licensed under the GPL-2.
+ *
+ * Based on: i2c-mux-pca954x.c
+ *
+ * Datasheet: http://cds.linear.com/docs/en/datasheet/4306.pdf
+ */
+
+#include <linux/device.h>
+#include <linux/gpio.h>
+#include <linux/gpio/consumer.h>
+#include <linux/gpio/driver.h>
+#include <linux/i2c-mux.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+#define LTC4305_MAX_NCHANS 2
+#define LTC4306_MAX_NCHANS 4
+
+#define LTC_REG_STATUS 0x0
+#define LTC_REG_CONFIG 0x1
+#define LTC_REG_MODE 0x2
+#define LTC_REG_SWITCH 0x3
+
+#define LTC_DOWNSTREAM_ACCL_EN BIT(6)
+#define LTC_UPSTREAM_ACCL_EN BIT(7)
+
+#define LTC_GPIO_ALL_INPUT 0xC0
+#define LTC_SWITCH_MASK 0xF0
+
+enum ltc_type {
+ ltc_4305,
+ ltc_4306,
+};
+
+struct chip_desc {
+ u8 nchans;
+ u8 num_gpios;
+};
+
+struct ltc4306 {
+ struct regmap *regmap;
+ struct gpio_chip gpiochip;
+ const struct chip_desc *chip;
+};
+
+static const struct chip_desc chips[] = {
+ [ltc_4305] = {
+ .nchans = LTC4305_MAX_NCHANS,
+ },
+ [ltc_4306] = {
+ .nchans = LTC4306_MAX_NCHANS,
+ .num_gpios = 2,
+ },
+};
+
+static bool ltc4306_is_volatile_reg(struct device *dev, unsigned int reg)
+{
+ return (reg == LTC_REG_CONFIG) ? true : false;
+}
+
+static const struct regmap_config ltc4306_regmap_config = {
+ .reg_bits = 8,
+ .val_bits = 8,
+ .max_register = LTC_REG_SWITCH,
+ .volatile_reg = ltc4306_is_volatile_reg,
+ .cache_type = REGCACHE_RBTREE,
Did you consider REGCACHE_FLAT? There are very few registers and no hole
in the map, and maintaining a tree seems like total overkill.
There is no reason to use REGCACHE_FLAT, in our case it will be a single
node.
+};
+
+static int ltc4306_gpio_get(struct gpio_chip *chip, unsigned int offset)
+{
+ struct ltc4306 *data = gpiochip_get_data(chip);
+ unsigned int val;
+ int ret;
+
+ ret = regmap_read(data->regmap, LTC_REG_CONFIG, &val);
+ if (ret < 0)
+ return ret;
+
+ return (val & BIT(1 - offset));
The outer parentheses do not add anything, and I think they might remain
from when you just removed a double negation at some point. But is it
good practice to indicate "high" with anything other than one? Sure, the
gpiolib function that wraps the ->get() op does the !! dance for you,
but even so, every single one of the half dozen random gpio providers I
looked at had code to coerce the value to 0/1 (or error). Which makes me
think you should also have it. And the gpio_chip documentation on ->get()
agrees with me...
I'll restore the double negations.
+}
+
+static void ltc4306_gpio_set(struct gpio_chip *chip, unsigned int offset,
+ int value)
+{
+ struct ltc4306 *data = gpiochip_get_data(chip);
+
+ regmap_update_bits(data->regmap, LTC_REG_CONFIG, BIT(5 - offset),
+ value ? BIT(5 - offset) : 0);
+}
+
+static int ltc4306_gpio_direction_input(struct gpio_chip *chip,
+ unsigned int offset)
+{
+ struct ltc4306 *data = gpiochip_get_data(chip);
+
+ return regmap_update_bits(data->regmap, LTC_REG_MODE,
+ BIT(7 - offset), BIT(7 - offset));
+}
+
+static int ltc4306_gpio_direction_output(struct gpio_chip *chip,
+ unsigned int offset, int value)
+{
+ struct ltc4306 *data = gpiochip_get_data(chip);
+
+ ltc4306_gpio_set(chip, offset, value);
+ return regmap_update_bits(data->regmap, LTC_REG_MODE,
+ BIT(7 - offset), 0);
+}
+
+static int ltc4306_gpio_set_config(struct gpio_chip *chip,
+ unsigned int offset, unsigned long config)
+{
+ struct ltc4306 *data = gpiochip_get_data(chip);
+ unsigned int val;
+
+ switch (pinconf_to_config_param(config)) {
+ case PIN_CONFIG_DRIVE_OPEN_DRAIN:
+ val = 0;
+ break;
+ case PIN_CONFIG_DRIVE_PUSH_PULL:
+ val = BIT(4 - offset);
+ break;
+ default:
+ return -ENOTSUPP;
+ }
+
+ return regmap_update_bits(data->regmap, LTC_REG_MODE,
+ BIT(4 - offset), val);
+}
+
+static int ltc4306_gpio_init(struct ltc4306 *data)
+{
+ struct device *dev = regmap_get_device(data->regmap);
+
+ if (!data->chip->num_gpios)
+ return 0;
+
+ data->gpiochip.label = dev_name(dev);
+ data->gpiochip.base = -1;
+ data->gpiochip.ngpio = data->chip->num_gpios;
+ data->gpiochip.parent = dev;
+ data->gpiochip.can_sleep = true;
+ data->gpiochip.direction_input = ltc4306_gpio_direction_input;
+ data->gpiochip.direction_output = ltc4306_gpio_direction_output;
I'm missing a get_direction op?
No - its purely optional - the vast majority of gpiochips don't
implement it.
linux/drivers/gpio$ grep -lr --include \*.c get_direction | wc
36 36 523
linux/drivers/gpio$ grep -Lr --include \*.c get_direction | wc
101 101 1461
+ data->gpiochip.get = ltc4306_gpio_get;
+ data->gpiochip.set = ltc4306_gpio_set;
+ data->gpiochip.set_config = ltc4306_gpio_set_config;
+ data->gpiochip.owner = THIS_MODULE;
+
+ /* gpiolib assumes all GPIOs default input */
+ regmap_write(data->regmap, LTC_REG_MODE, LTC_GPIO_ALL_INPUT);
+
+ return devm_gpiochip_add_data(dev, &data->gpiochip, data);
+}
+
+static int ltc4306_select_mux(struct i2c_mux_core *muxc, u32 chan)
+{
+ struct ltc4306 *data = i2c_mux_priv(muxc);
+
+ return regmap_update_bits(data->regmap, LTC_REG_SWITCH,
+ LTC_SWITCH_MASK, BIT(7 - chan));
Since the bits outside the mask are ignored for writes, I'd go with
regmap_write. Especially since those bits are volatile, which admittedly
will not have much impact until there is a need to read those volatile
bits outside the mask. But still.
Yes they are volatile - but not declared as such.
So regmap cache just ignores them.
And we totally ignore these RONLY status bits, too.
regmap_write() will always write and ignore the cache, while
regmap_update_bits() uses the cached value.
Are these callbacks guaranteed to be never called with the same CHAN
sequentially? if yes - use regmap_write() otherwise its more efficient
to use regmap_update_bits().
+}
+
+static int ltc4306_deselect_mux(struct i2c_mux_core *muxc, u32 chan)
+{
+ struct ltc4306 *data = i2c_mux_priv(muxc);
+
+ return regmap_update_bits(data->regmap, LTC_REG_SWITCH,
+ LTC_SWITCH_MASK, 0);
Dito.
+}
+
+static const struct i2c_device_id ltc4306_id[] = {
+ { "ltc4305", ltc_4305 },
+ { "ltc4306", ltc_4306 },
+ { }
+};
+MODULE_DEVICE_TABLE(i2c, ltc4306_id);
+
+static const struct of_device_id ltc4306_of_match[] = {
+ { .compatible = "lltc,ltc4305", .data = &chips[ltc_4305] },
+ { .compatible = "lltc,ltc4306", .data = &chips[ltc_4306] },
+ { }
+};
+MODULE_DEVICE_TABLE(of, ltc4306_of_match);
+
+static int ltc4306_probe(struct i2c_client *client,
+ const struct i2c_device_id *id)
+{
+ struct i2c_adapter *adap = to_i2c_adapter(client->dev.parent);
+ struct device_node *of_node = client->dev.of_node;
+ struct i2c_mux_core *muxc;
+ struct ltc4306 *data;
+ struct gpio_desc *gpio;
+ bool idle_disc = false;
+ int num, ret;
+
+ if (of_node)
+ idle_disc = of_property_read_bool(of_node,
+ "i2c-mux-idle-disconnect");
+
+ muxc = i2c_mux_alloc(adap, &client->dev,
+ LTC4306_MAX_NCHANS, sizeof(*data),
Hmmm, I didn't see this before, but if you do some more rearranging, it
should be possible to replace LTC4306_MAX_NCHANS with data->chip->nchans
and reduce resource waste for ltc4305. But it's just storage for two
pointers which is really really minor... Feel free to ignore.
But you want to set a good example, right :-)
+ I2C_MUX_LOCKED, ltc4306_select_mux,
+ idle_disc ? ltc4306_deselect_mux : NULL);
+ if (!muxc)
+ return -ENOMEM;
+ data = i2c_mux_priv(muxc);
+
+ i2c_set_clientdata(client, muxc);
+
+ data->regmap = devm_regmap_init_i2c(client, <c4306_regmap_config);
+ if (IS_ERR(data->regmap)) {
+ ret = PTR_ERR(data->regmap);
+ dev_err(&client->dev, "Failed to allocate register map: %d\n",
+ ret);
+ return ret;
+ }
+
+ /* Reset and enable the mux if an enable GPIO is specified. */
+ gpio = devm_gpiod_get_optional(&client->dev, "enable", GPIOD_OUT_LOW);
+ if (IS_ERR(gpio))
+ return PTR_ERR(gpio);
+
+ if (gpio) {
+ udelay(1);
+ gpiod_set_value(gpio, 1);
+ }
+
+ /*
+ * Write the mux register at addr to verify
+ * that the mux is in fact present. This also
+ * initializes the mux to disconnected state.
+ */
+ if (regmap_write(data->regmap, LTC_REG_SWITCH, 0) < 0) {
+ dev_warn(&client->dev, "probe failed\n");
+ return -ENODEV;
+ }
+
+ if (of_node) {
+ unsigned int val = 0;
+
+ data->chip = of_device_get_match_data(&client->dev);
+
+ if (of_property_read_bool(of_node,
+ "ltc,downstream-accelerators-enable"))
+ val |= LTC_DOWNSTREAM_ACCL_EN;
+
+ if (of_property_read_bool(of_node,
+ "ltc,upstream-accelerators-enable"))
+ val |= LTC_UPSTREAM_ACCL_EN;
+
+ if (regmap_write(data->regmap, LTC_REG_CONFIG, val) < 0)
+ return -ENODEV;
+ } else {
+ data->chip = &chips[id->driver_data];
+ }
+
+ ret = ltc4306_gpio_init(data);
+ if (ret < 0)
+ return ret;
+
+ /* Now create an adapter for each channel */
+ for (num = 0; num < data->chip->nchans; num++) {
+ ret = i2c_mux_add_adapter(muxc, 0, num, 0);
+ if (ret) {
+ i2c_mux_del_adapters(muxc);
+ return ret;
+ }
+ }
+
+ dev_info(&client->dev,
+ "registered %d multiplexed busses for I2C switch %s\n",
+ num, client->name);
+
+ return 0;
+}
+
+static int ltc4306_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 ltc4306_driver = {
+ .driver = {
+ .name = "ltc4306",
+ .of_match_table = of_match_ptr(ltc4306_of_match),
+ },
+ .probe = ltc4306_probe,
+ .remove = ltc4306_remove,
+ .id_table = ltc4306_id,
+};
+
+module_i2c_driver(ltc4306_driver);
+
+MODULE_AUTHOR("Michael Hennerich <michael.hennerich@xxxxxxxxxx>");
+MODULE_DESCRIPTION("Linear Technology LTC4306, LTC4305 I2C mux/switch driver");
+MODULE_LICENSE("GPL v2");
--
Greetings,
Michael
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