[U-Boot] [PATCH RESEND 4/9] w1: Add 1-Wire gpio driver

[Maxime Ripard]

On Thu, Nov 10, 2016 at 02:35:46PM +0100, Michal Simek wrote:
> On 8.11.2016 11:19, Maxime Ripard wrote:
> > Add a bus driver for bitbanging a 1-Wire bus over a GPIO.
> > 
> > Signed-off-by: Maxime Ripard <maxime.ripard at free-electrons.com>
> > ---
> >  drivers/w1/Kconfig   |   6 ++-
> >  drivers/w1/Makefile  |   1 +-
> >  drivers/w1/w1-gpio.c | 160 ++++++++++++++++++++++++++++++++++++++++++++-
> >  3 files changed, 167 insertions(+), 0 deletions(-)
> >  create mode 100644 drivers/w1/w1-gpio.c
> > 
> > diff --git a/drivers/w1/Kconfig b/drivers/w1/Kconfig
> > index 0c056b4c06a9..ccc3ae15db86 100644
> > --- a/drivers/w1/Kconfig
> > +++ b/drivers/w1/Kconfig
> > @@ -12,6 +12,12 @@ config W1
> >  
> >  if W1
> >  
> > +config W1_GPIO
> > +	bool "Enable 1-Wire GPIO bitbanging"
> > +	depends on DM_GPIO
> > +	help
> > +	  Emulate a 1-Wire bus using a GPIO.
> > +
> >  endif
> >  
> >  endmenu
> > diff --git a/drivers/w1/Makefile b/drivers/w1/Makefile
> > index 26820fa209e1..7fd8697f8419 100644
> > --- a/drivers/w1/Makefile
> > +++ b/drivers/w1/Makefile
> > @@ -1,2 +1,3 @@
> >  obj-$(CONFIG_W1) += w1-uclass.o
> >  
> > +obj-$(CONFIG_W1_GPIO) += w1-gpio.o
> > diff --git a/drivers/w1/w1-gpio.c b/drivers/w1/w1-gpio.c
> > new file mode 100644
> > index 000000000000..091849162533
> > --- /dev/null
> > +++ b/drivers/w1/w1-gpio.c
> > @@ -0,0 +1,160 @@
> > +/*
> > + * Copyright (c) 2015 Free Electrons
> > + * Copyright (c) 2015 NextThing Co
> > + *
> > + * Maxime Ripard <maxime.ripard at free-electrons.com>
> > + *
> > + * SPDX-License-Identifier:	GPL-2.0+
> > + */
> > +
> > +#include <common.h>
> > +#include <dm.h>
> > +#include <w1.h>
> > +
> > +#include <asm/gpio.h>
> > +
> > +
> > +#define W1_TIMING_A	6
> > +#define W1_TIMING_B	64
> > +#define W1_TIMING_C	60
> > +#define W1_TIMING_D	10
> > +#define W1_TIMING_E	9
> > +#define W1_TIMING_F	55
> > +#define W1_TIMING_G	0
> > +#define W1_TIMING_H	480
> > +#define W1_TIMING_I	70
> > +#define W1_TIMING_J	410
> > +
> > +struct w1_gpio_pdata {
> > +	struct gpio_desc	gpio;
> > +	u64			search_id;
> > +};
> > +
> > +static bool w1_gpio_read_bit(struct udevice *dev)
> > +{
> > +	struct w1_gpio_pdata *pdata = dev_get_platdata(dev);
> > +	int val;
> > +
> > +	dm_gpio_set_dir_flags(&pdata->gpio, GPIOD_IS_OUT);
> > +	udelay(W1_TIMING_A);
> > +
> > +	dm_gpio_set_dir_flags(&pdata->gpio, GPIOD_IS_IN);
> > +	udelay(W1_TIMING_E);
> > +
> > +	val = dm_gpio_get_value(&pdata->gpio);
> > +	udelay(W1_TIMING_F);
> > +
> > +	return val;
> > +}
> > +
> > +static u8 w1_gpio_read_byte(struct udevice *dev)
> > +{
> > +	int i;
> > +	u8 ret = 0;
> > +
> > +	for (i = 0; i < 8; ++i)
> > +		ret |= (w1_gpio_read_bit(dev) ? 1 : 0) << i;
> > +
> > +	return ret;
> > +}
> > +
> > +static void w1_gpio_write_bit(struct udevice *dev, bool bit)
> > +{
> > +	struct w1_gpio_pdata *pdata = dev_get_platdata(dev);
> > +
> > +	dm_gpio_set_dir_flags(&pdata->gpio, GPIOD_IS_OUT);
> > +
> > +	bit ? udelay(W1_TIMING_A) : udelay(W1_TIMING_C);
> > +
> > +	dm_gpio_set_value(&pdata->gpio, 1);
> > +
> > +	bit ? udelay(W1_TIMING_B) : udelay(W1_TIMING_D);
> > +}
> > +
> > +static void w1_gpio_write_byte(struct udevice *dev, u8 byte)
> > +{
> > +	int i;
> > +
> > +	for (i = 0; i < 8; ++i)
> > +		w1_gpio_write_bit(dev, (byte >> i) & 0x1);
> > +}
> > +
> > +static bool w1_gpio_reset(struct udevice *dev)
> > +{
> > +	struct w1_gpio_pdata *pdata = dev_get_platdata(dev);
> > +	int val;
> > +
> > +	dm_gpio_set_dir_flags(&pdata->gpio, GPIOD_IS_OUT | GPIOD_IS_OUT_ACTIVE);
> > +	udelay(W1_TIMING_G);
> > +
> > +	dm_gpio_set_value(&pdata->gpio, 0);
> > +	udelay(W1_TIMING_H);
> > +
> > +	dm_gpio_set_dir_flags(&pdata->gpio, GPIOD_IS_IN);
> > +	udelay(W1_TIMING_I);
> > +
> > +	val = dm_gpio_get_value(&pdata->gpio);
> > +	udelay(W1_TIMING_J);
> > +
> > +	return val;
> > +}
> > +
> > +static u8 w1_gpio_triplet(struct udevice *dev, bool bdir)
> > +{
> > +	u8 id_bit   = w1_gpio_read_bit(dev);
> > +	u8 comp_bit = w1_gpio_read_bit(dev);
> > +	u8 retval;
> > +
> > +	if (id_bit && comp_bit)
> > +		return 0x03;  /* error */
> > +
> > +	if (!id_bit && !comp_bit) {
> > +		/* Both bits are valid, take the direction given */
> > +		retval = bdir ? 0x04 : 0;
> > +	} else {
> > +		/* Only one bit is valid, take that direction */
> > +		bdir = id_bit;
> > +		retval = id_bit ? 0x05 : 0x02;
> > +	}
> > +
> > +	w1_gpio_write_bit(dev, bdir);
> > +	return retval;
> > +}
> > +
> > +
> > +static const struct w1_ops w1_gpio_ops = {
> > +	.read_byte	= w1_gpio_read_byte,
> > +	.reset		= w1_gpio_reset,
> > +	.triplet	= w1_gpio_triplet,
> > +	.write_byte	= w1_gpio_write_byte,
> > +};
> > +
> > +static int w1_gpio_ofdata_to_platdata(struct udevice *dev)
> > +{
> > +	struct w1_gpio_pdata *pdata = dev_get_platdata(dev);
> > +	int ret;
> > +
> > +	ret = gpio_request_by_name(dev, "gpios", 0, &pdata->gpio, 0);
> > +	if (ret < 0)
> > +		goto error;
> > +
> > +	return 0;
> > +
> > +error:
> > +	printf("Error claiming GPIO %d\n", ret);
> > +	return ret;
> > +};
> > +
> > +static const struct udevice_id w1_gpio_id[] = {
> > +	{ "w1-gpio", 0 },
> > +	{ },
> > +};
> > +
> > +U_BOOT_DRIVER(w1_gpio_drv) = {
> > +	.id				= UCLASS_W1,
> > +	.name				= "w1_gpio_drv",
> > +	.of_match			= w1_gpio_id,
> > +	.ofdata_to_platdata		= w1_gpio_ofdata_to_platdata,
> > +	.ops				= &w1_gpio_ops,
> > +	.platdata_auto_alloc_size	= sizeof(struct w1_gpio_pdata),
> > +};
> > 
> 
> Has someone test this on different HW?

I didn't, but it looks pretty generic.

The only thing you have to make sure is that you can respect the
rather tight timing constraints of the bus. That rules out a GPIO on
an I2C expander for example.

> As I went through the series will be good to have cmd/w1.c to be
> able to test that devices.

Ack.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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