[PATCH 0/2] Technologic I2C-FPGA gpio support

[PATCH 0/2] Technologic I2C-FPGA gpio support

[Lucile Quirion]

This driver aims to support all Technologic Systems's boards embedding FPGA
GPIOs with an I2C interface.

Lucile Quirion (2):
  gpio: add bindings for Technologic I2C-FPGA gpio controller
  gpio: add Technologic I2C-FPGA gpio support

 .../devicetree/bindings/gpio/gpio-ts4900.txt       |  29 +++
 drivers/gpio/Kconfig                               |   6 +
 drivers/gpio/Makefile                              |   1 +
 drivers/gpio/gpio-ts4900.c                         | 238 +++++++++++++++++++++
 4 files changed, 274 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/gpio/gpio-ts4900.txt
 create mode 100644 drivers/gpio/gpio-ts4900.c

-- 
2.5.5

[PATCH 1/2] gpio: add bindings for Technologic I2C-FPGA gpio controller

[Lucile Quirion]

Device tree binding documentation for Technologic's I2C-FPGA GPIO
controller.

Signed-off-by: Lucile Quirion <lucile.quirion@savoirfairelinux.com>
---
 .../devicetree/bindings/gpio/gpio-ts4900.txt       | 29 ++++++++++++++++++++++
 1 file changed, 29 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/gpio/gpio-ts4900.txt

diff --git a/Documentation/devicetree/bindings/gpio/gpio-ts4900.txt b/Documentation/devicetree/bindings/gpio/gpio-ts4900.txt
new file mode 100644
index 0000000..e114f6f
--- /dev/null
+++ b/Documentation/devicetree/bindings/gpio/gpio-ts4900.txt
@@ -0,0 +1,29 @@
+* Technologic Systems I2C-FPGA's GPIO controller bindings
+
+This bindings describes the GPIO controller for Technologic's FPGA core.
+TS-4900's FPGA encodes the GPIO state on 3 bits, whereas the TS-7970's FPGA
+uses 2 bits: it doesn't use a dedicated input bit.
+
+Required properties:
+- compatible: Should be one of the following
+		"technologic,ts4900-gpio"
+		"technologic,ts7970-gpio"
+- reg: Physical base address of the controller and length
+       of memory mapped region.
+- #gpio-cells: Should be two. The first cell is the pin number.
+- gpio-controller: Marks the device node as a gpio controller.
+
+Optional property:
+- ngpios: see "gpio.txt".
+
+Example:
+
+&i2c2 {
+	gpio8: ts4900-gpio@28 {
+		compatible = "technologic,ts4900-gpio";
+		reg = <0x28>;
+		#gpio-cells = <2>;
+		gpio-controller;
+		ngpios = <32>;
+	};
+};
-- 
2.5.5

[PATCH 2/2] gpio: add Technologic I2C-FPGA gpio support

[Lucile Quirion]

This driver is generic and aims to support all Technologic Systems's
boards embedding FPGA GPIOs with an I2C interface.

This driver supports TS-4900, TS-7970, TS-7990 and TS-4100 series.

Signed-off-by: Lucile Quirion <lucile.quirion@savoirfairelinux.com>
---
 drivers/gpio/Kconfig       |   6 ++
 drivers/gpio/Makefile      |   1 +
 drivers/gpio/gpio-ts4900.c | 238 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 245 insertions(+)
 create mode 100644 drivers/gpio/gpio-ts4900.c

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 98dd47a..459fb71 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -779,6 +779,12 @@ config GPIO_TPIC2810
 	  To compile this driver as a module, choose M here: the module will
 	  be called gpio-tpic2810.
 
+config GPIO_TS4900
+	bool "Technologic Systems FPGA I2C GPIO"
+	help
+	  Say yes here to enabled the GPIO driver for Technologic's FPGA core.
+	  Series supported include TS-4100, TS-4900, TS-7970 and TS-7990.
+
 endmenu
 
 menu "MFD GPIO expanders"
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 2a035ed..4dcc21f 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -110,6 +110,7 @@ obj-$(CONFIG_GPIO_TPS6586X)	+= gpio-tps6586x.o
 obj-$(CONFIG_GPIO_TPS65910)	+= gpio-tps65910.o
 obj-$(CONFIG_GPIO_TPS65912)	+= gpio-tps65912.o
 obj-$(CONFIG_GPIO_TS4800)	+= gpio-ts4800.o
+obj-$(CONFIG_GPIO_TS4900)	+= gpio-ts4900.o
 obj-$(CONFIG_GPIO_TS5500)	+= gpio-ts5500.o
 obj-$(CONFIG_GPIO_TWL4030)	+= gpio-twl4030.o
 obj-$(CONFIG_GPIO_TWL6040)	+= gpio-twl6040.o
diff --git a/drivers/gpio/gpio-ts4900.c b/drivers/gpio/gpio-ts4900.c
new file mode 100644
index 0000000..104d1e0
--- /dev/null
+++ b/drivers/gpio/gpio-ts4900.c
@@ -0,0 +1,238 @@
+/*
+ * Digital I/O driver for Technologic Systems I2C FPGA Core
+ *
+ * Copyright (C) 2015 Technologic Systems
+ * Copyright (C) 2016 Savoir-Faire Linux
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether expressed or implied; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License version 2 for more details.
+ */
+
+#include <linux/gpio/driver.h>
+#include <linux/i2c.h>
+#include <linux/of_device.h>
+#include <linux/module.h>
+
+#define DEFAULT_PIN_NUMBER	32
+/*
+ * Register bits used by the GPIO device
+ * Some boards, such as TS-7970 do not have a separate input bit
+ */
+#define TS4900_GPIO_OE		0x01
+#define TS4900_GPIO_OD		0x02
+#define TS4900_GPIO_ID		0x04
+#define TS7970_GPIO_ID		0x02
+
+struct ts4900_gpio_priv {
+	struct i2c_client *client;
+	struct gpio_chip gpio_chip;
+	unsigned int input_bit;
+};
+
+static int ts4900_gpio_write(struct i2c_client *client, u16 addr, u8 data)
+{
+	struct i2c_msg msg;
+	u8 buf[3];
+	int ret;
+
+	buf[0] = addr >> 8;
+	buf[1] = addr & 0xFF;
+	buf[2] = data;
+
+	msg.addr = client->addr;
+	msg.flags = 0;
+	msg.len = 3;
+	msg.buf = buf;
+
+	ret = i2c_transfer(client->adapter, &msg, 1);
+	if (ret != 1) {
+		dev_err(&client->dev, "%s: write error, ret=%d\n",
+			__func__, ret);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static int ts4900_gpio_read(struct i2c_client *client, u16 addr)
+{
+	struct i2c_msg msgs[2];
+	u8 buf[2];
+	int ret;
+
+	buf[0] = addr >> 8;
+	buf[1] = addr & 0xFF;
+
+	msgs[0].addr = client->addr;
+	msgs[0].flags = 0;
+	msgs[0].len = 2;
+	msgs[0].buf = buf;
+
+	msgs[1].addr = client->addr;
+	msgs[1].flags = I2C_M_RD;
+	msgs[1].len = 1;
+	msgs[1].buf = buf;
+
+	ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
+	if (ret != ARRAY_SIZE(msgs)) {
+		dev_err(&client->dev, "%s: read error, ret=%d\n",
+			__func__, ret);
+		return -EIO;
+	}
+
+	return buf[0];
+}
+
+static int __ts4900_gpio_direction_output(struct i2c_client *client, int gpio,
+				     int value)
+{
+	u8 reg = 0;
+
+	if (value)
+		reg = TS4900_GPIO_OD | TS4900_GPIO_OE;
+	else
+		reg = TS4900_GPIO_OE;
+
+	return ts4900_gpio_write(client, gpio, reg);
+}
+
+static int ts4900_gpio_direction_input(struct gpio_chip *chip,
+				       unsigned int offset)
+{
+	struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);
+
+	/*
+	 * This will clear the output enable bit, the other bits are
+	 * dontcare when this is cleared
+	 */
+	return ts4900_gpio_write(priv->client, offset, 0);
+}
+
+static int ts4900_gpio_direction_output(struct gpio_chip *chip,
+					unsigned int offset, int value)
+{
+	struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);
+
+	return __ts4900_gpio_direction_output(priv->client, offset, value);
+}
+
+static int ts4900_gpio_get(struct gpio_chip *chip, unsigned int offset)
+{
+	struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);
+	int ret;
+	u8 reg;
+
+	reg = ts4900_gpio_read(priv->client, offset);
+
+	ret = (reg & priv->input_bit) ? 1 : 0;
+
+	return ret;
+}
+
+static void ts4900_gpio_set(struct gpio_chip *chip, unsigned int offset,
+			    int value)
+{
+	struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);
+
+	__ts4900_gpio_direction_output(priv->client, offset, value);
+}
+
+static struct gpio_chip template_chip = {
+	.label			= "ts4900-gpio",
+	.owner			= THIS_MODULE,
+	.direction_input	= ts4900_gpio_direction_input,
+	.direction_output	= ts4900_gpio_direction_output,
+	.get			= ts4900_gpio_get,
+	.set			= ts4900_gpio_set,
+	.base			= -1,
+	.can_sleep		= true,
+};
+
+static const struct of_device_id ts4900_gpio_of_match_table[] = {
+	{
+		.compatible = "technologic,ts4900-gpio",
+		.data = (void *)TS4900_GPIO_ID,
+	}, {
+		.compatible = "technologic,ts7970-gpio",
+		.data = (void *)TS7970_GPIO_ID,
+	},
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, ts4900_gpio_of_match_table);
+
+static int ts4900_gpio_probe(struct i2c_client *client,
+			const struct i2c_device_id *id)
+{
+	const struct of_device_id *match;
+	struct ts4900_gpio_priv *priv;
+	u32 ngpio;
+	int ret;
+
+	if (!i2c_check_functionality(client->adapter,
+				     I2C_FUNC_SMBUS_BYTE_DATA))
+		return -EIO;
+
+	match = of_match_device(ts4900_gpio_of_match_table, &client->dev);
+	if (!match)
+		return -EINVAL;
+
+	if (of_property_read_u32(client->dev.of_node, "ngpios", &ngpio))
+		ngpio = DEFAULT_PIN_NUMBER;
+
+	priv = devm_kzalloc(&client->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	i2c_set_clientdata(client, priv);
+
+	priv->client = client;
+	priv->gpio_chip = template_chip;
+	priv->gpio_chip.label = "ts4900-gpio";
+	priv->gpio_chip.ngpio = ngpio;
+	priv->gpio_chip.parent = &client->dev;
+	priv->input_bit = (uintptr_t)match->data;
+
+	ret = gpiochip_add_data(&priv->gpio_chip, priv);
+	if (ret < 0) {
+		dev_err(&client->dev, "Unable to register gpiochip\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static int ts4900_gpio_remove(struct i2c_client *client)
+{
+	struct ts4900_gpio_priv *priv = i2c_get_clientdata(client);
+
+	gpiochip_remove(&priv->gpio_chip);
+
+	return 0;
+}
+
+static const struct i2c_device_id ts4900_gpio_id_table[] = {
+	{ "ts4900-gpio", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(i2c, ts4900_gpio_id_table);
+
+static struct i2c_driver ts4900_gpio_driver = {
+	.driver = {
+		.name = "ts4900-gpio",
+		.of_match_table = ts4900_gpio_of_match_table,
+	},
+	.probe = ts4900_gpio_probe,
+	.remove = ts4900_gpio_remove,
+	.id_table = ts4900_gpio_id_table,
+};
+module_i2c_driver(ts4900_gpio_driver);
+
+MODULE_AUTHOR("Technologic Systems");
+MODULE_DESCRIPTION("GPIO interface for Technologic Systems I2C-FPGA core");
+MODULE_LICENSE("GPL");
-- 
2.5.5

Re: [PATCH 2/2] gpio: add Technologic I2C-FPGA gpio support

[Paul Gortmaker]

On Fri, Aug 5, 2016 at 10:41 AM, Lucile Quirion
<lucile.quirion@savoirfairelinux.com> wrote:
> This driver is generic and aims to support all Technologic Systems's
> boards embedding FPGA GPIOs with an I2C interface.
>
> This driver supports TS-4900, TS-7970, TS-7990 and TS-4100 series.
>
> Signed-off-by: Lucile Quirion <lucile.quirion@savoirfairelinux.com>
> ---
>  drivers/gpio/Kconfig       |   6 ++
>  drivers/gpio/Makefile      |   1 +
>  drivers/gpio/gpio-ts4900.c | 238 +++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 245 insertions(+)
>  create mode 100644 drivers/gpio/gpio-ts4900.c
>
> diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
> index 98dd47a..459fb71 100644
> --- a/drivers/gpio/Kconfig
> +++ b/drivers/gpio/Kconfig
> @@ -779,6 +779,12 @@ config GPIO_TPIC2810
>           To compile this driver as a module, choose M here: the module will
>           be called gpio-tpic2810.
>
> +config GPIO_TS4900
> +       bool "Technologic Systems FPGA I2C GPIO"

Please don't use module.h and MODULE_<xyz> macros in drivers that are bool.

Either delete all the module related stuff and use a builtin registration fcn,
or use a tristate Kconfig if there is a genuine use case for a modular driver.

Thanks,
Paul.
--

> +       help
> +         Say yes here to enabled the GPIO driver for Technologic's FPGA core.
> +         Series supported include TS-4100, TS-4900, TS-7970 and TS-7990.
> +
>  endmenu
>
>  menu "MFD GPIO expanders"
> diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
> index 2a035ed..4dcc21f 100644
> --- a/drivers/gpio/Makefile
> +++ b/drivers/gpio/Makefile
> @@ -110,6 +110,7 @@ obj-$(CONFIG_GPIO_TPS6586X) += gpio-tps6586x.o
>  obj-$(CONFIG_GPIO_TPS65910)    += gpio-tps65910.o
>  obj-$(CONFIG_GPIO_TPS65912)    += gpio-tps65912.o
>  obj-$(CONFIG_GPIO_TS4800)      += gpio-ts4800.o
> +obj-$(CONFIG_GPIO_TS4900)      += gpio-ts4900.o
>  obj-$(CONFIG_GPIO_TS5500)      += gpio-ts5500.o
>  obj-$(CONFIG_GPIO_TWL4030)     += gpio-twl4030.o
>  obj-$(CONFIG_GPIO_TWL6040)     += gpio-twl6040.o
> diff --git a/drivers/gpio/gpio-ts4900.c b/drivers/gpio/gpio-ts4900.c
> new file mode 100644
> index 0000000..104d1e0
> --- /dev/null
> +++ b/drivers/gpio/gpio-ts4900.c
> @@ -0,0 +1,238 @@
> +/*
> + * Digital I/O driver for Technologic Systems I2C FPGA Core
> + *
> + * Copyright (C) 2015 Technologic Systems
> + * Copyright (C) 2016 Savoir-Faire Linux
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed "as is" WITHOUT ANY WARRANTY of any
> + * kind, whether expressed or implied; without even the implied warranty
> + * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License version 2 for more details.
> + */
> +
> +#include <linux/gpio/driver.h>
> +#include <linux/i2c.h>
> +#include <linux/of_device.h>
> +#include <linux/module.h>
> +

[...]

> +static const struct i2c_device_id ts4900_gpio_id_table[] = {
> +       { "ts4900-gpio", },
> +       { /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(i2c, ts4900_gpio_id_table);
> +
> +static struct i2c_driver ts4900_gpio_driver = {
> +       .driver = {
> +               .name = "ts4900-gpio",
> +               .of_match_table = ts4900_gpio_of_match_table,
> +       },
> +       .probe = ts4900_gpio_probe,
> +       .remove = ts4900_gpio_remove,
> +       .id_table = ts4900_gpio_id_table,
> +};
> +module_i2c_driver(ts4900_gpio_driver);
> +
> +MODULE_AUTHOR("Technologic Systems");
> +MODULE_DESCRIPTION("GPIO interface for Technologic Systems I2C-FPGA core");
> +MODULE_LICENSE("GPL");
> --
> 2.5.5
>

Re: [PATCH 1/2] gpio: add bindings for Technologic I2C-FPGA gpio controller

[Linus Walleij]

On Fri, Aug 5, 2016 at 4:41 PM, Lucile Quirion
<lucile.quirion@savoirfairelinux.com> wrote:

> Device tree binding documentation for Technologic's I2C-FPGA GPIO
> controller.
>
> Signed-off-by: Lucile Quirion <lucile.quirion@savoirfairelinux.com>
(...)

> +Optional property:
> +- ngpios: see "gpio.txt".

gpio.txt gives examples of what this is used for. Detail why it is used
for this specific hardware.

Yours,
Linus Walleij

Re: [PATCH 2/2] gpio: add Technologic I2C-FPGA gpio support

[Linus Walleij]

On Fri, Aug 5, 2016 at 4:41 PM, Lucile Quirion
<lucile.quirion@savoirfairelinux.com> wrote:

> This driver is generic and aims to support all Technologic Systems's
> boards embedding FPGA GPIOs with an I2C interface.
>
> This driver supports TS-4900, TS-7970, TS-7990 and TS-4100 series.
>
> Signed-off-by: Lucile Quirion <lucile.quirion@savoirfairelinux.com>
(...)

> +static int ts4900_gpio_write(struct i2c_client *client, u16 addr, u8 data)
> +{
> +       struct i2c_msg msg;
> +       u8 buf[3];
> +       int ret;
> +
> +       buf[0] = addr >> 8;
> +       buf[1] = addr & 0xFF;
> +       buf[2] = data;
> +
> +       msg.addr = client->addr;
> +       msg.flags = 0;
> +       msg.len = 3;
> +       msg.buf = buf;
> +
> +       ret = i2c_transfer(client->adapter, &msg, 1);
> +       if (ret != 1) {
> +               dev_err(&client->dev, "%s: write error, ret=%d\n",
> +                       __func__, ret);
> +               return -EIO;
> +       }
> +
> +       return 0;
> +}
> +
> +static int ts4900_gpio_read(struct i2c_client *client, u16 addr)
> +{
> +       struct i2c_msg msgs[2];
> +       u8 buf[2];
> +       int ret;
> +
> +       buf[0] = addr >> 8;
> +       buf[1] = addr & 0xFF;
> +
> +       msgs[0].addr = client->addr;
> +       msgs[0].flags = 0;
> +       msgs[0].len = 2;
> +       msgs[0].buf = buf;
> +
> +       msgs[1].addr = client->addr;
> +       msgs[1].flags = I2C_M_RD;
> +       msgs[1].len = 1;
> +       msgs[1].buf = buf;
> +
> +       ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
> +       if (ret != ARRAY_SIZE(msgs)) {
> +               dev_err(&client->dev, "%s: read error, ret=%d\n",
> +                       __func__, ret);
> +               return -EIO;
> +       }
> +
> +       return buf[0];
> +}

It appears that you can very clearly replace this stuff with an
I2C regmap. If you look in drivers/base/regmap/regmap-i2c.c
you can see that you're just reimplementing regmaps marshalling.

Look at other drivers using I2C regmap for inspiration, e.g.
drivers/mfd/stw481x.c.

select REGMAP_I2C #include <linux/regmap.h> and start by implementing
devm_regmap_init_i2c() etc.

> +static int __ts4900_gpio_direction_output(struct i2c_client *client, int gpio,
> +                                    int value)

I don't like __prefixed functions. Come up with a better name.

> +{
> +       u8 reg = 0;
> +
> +       if (value)
> +               reg = TS4900_GPIO_OD | TS4900_GPIO_OE;
> +       else
> +               reg = TS4900_GPIO_OE;
> +
> +       return ts4900_gpio_write(client, gpio, reg);
> +}

TS4900_GPIO_OD sounds like you can switch the output
between push-pull and open drain and here you are just open
coding all outputs to be open drain. That is confusing.

For controlling open drain implement
.set_single_ended() in the GPIO chip and let consumers
explicitly request that they want their line open drain.

If "OD" does not mean open drain it is extremely confusing
but OK then I am wrong...

> +static int ts4900_gpio_direction_input(struct gpio_chip *chip,
> +                                      unsigned int offset)
> +static int ts4900_gpio_direction_output(struct gpio_chip *chip,
> +                                       unsigned int offset, int value)

Also implement ts4900_gpio_get_direction()

> +static int ts4900_gpio_get(struct gpio_chip *chip, unsigned int offset)
> +{
> +       struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);
> +       int ret;
> +       u8 reg;
> +
> +       reg = ts4900_gpio_read(priv->client, offset);
> +
> +       ret = (reg & priv->input_bit) ? 1 : 0;
> +
> +       return ret;

Just replace the two last lines with:

return !!(reg & priv->input_bit);

> +static void ts4900_gpio_set(struct gpio_chip *chip, unsigned int offset,
> +                           int value)
> +{
> +       struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);
> +
> +       __ts4900_gpio_direction_output(priv->client, offset, value);
> +}

Why should you always set the direction to output when setting
an output value? It doesn't make sense. Make the functions
do one thing. .direction_output() sets an output value at the
same time, but .set() should not force the line as output.

(...)
> +       ret = gpiochip_add_data(&priv->gpio_chip, priv);

Use devm_gpiochip_add_data()

> +static int ts4900_gpio_remove(struct i2c_client *client)
> +{
> +       struct ts4900_gpio_priv *priv = i2c_get_clientdata(client);
> +
> +       gpiochip_remove(&priv->gpio_chip);
> +
> +       return 0;
> +}

Then this is not needed at all (handled by devm*)

Yours,
Linus Walleij