[U-Boot] [PATCH v4 02/34] w1: Add 1-Wire gpio driver

Eugen Hristev
2018-09-18T07:35:25Z

From: Maxime Ripard <maxime.ripard@free-electrons.com>

Add a bus driver for bitbanging a 1-Wire bus over a GPIO.

Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
[eugen.hristev at microchip.com: fixed some issues]
Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
---
drivers/w1/Kconfig | 7 ++
drivers/w1/Makefile | 2 +
drivers/w1/w1-gpio.c | 176 +++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 185 insertions(+)
create mode 100644 drivers/w1/w1-gpio.c

diff --git a/drivers/w1/Kconfig b/drivers/w1/Kconfig
index 64b27c6..d6e0457 100644
--- a/drivers/w1/Kconfig
+++ b/drivers/w1/Kconfig
@@ -13,6 +13,13 @@ config W1

if W1

+config W1_GPIO
+ bool "Enable 1-wire GPIO bitbanging"
+ default no
+ 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 f81693b..7fd8697 100644
--- a/drivers/w1/Makefile
+++ b/drivers/w1/Makefile
@@ -1 +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 0000000..5e5d6b3
--- /dev/null
+++ b/drivers/w1/w1-gpio.c
@@ -0,0 +1,176 @@
+/* SPDX-License-Identifier: GPL-2.0+
+ *
+ * Copyright (c) 2015 Free Electrons
+ * Copyright (c) 2015 NextThing Co
+ *
+ * Maxime Ripard <maxime.ripard@free-electrons.com>
+ *
+ */
+
+#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);
+ if (val < 0)
+ debug("error in retrieving GPIO value");
+ 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;
+
+ /* initiate the reset pulse. first we must pull the bus to low */
+ 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);
+ /* wait for the specified time with the bus kept low */
+ udelay(W1_TIMING_H);
+
+ /* now we must read the presence pulse */
+ dm_gpio_set_dir_flags(&pdata->gpio, GPIOD_IS_IN);
+ udelay(W1_TIMING_I);
+
+ val = dm_gpio_get_value(&pdata->gpio);
+ if (val < 0)
+ debug("error in retrieving GPIO value");
+
+ /* if nobody pulled the bus down , it means nobody is on the bus */
+ if (val != 0)
+ return 1;
+ /* we have the bus pulled down, let's wait for the specified presence time */
+ udelay(W1_TIMING_J);
+
+ /* read again, the other end should leave the bus free */
+ val = dm_gpio_get_value(&pdata->gpio);
+ if (val < 0)
+ debug("error in retrieving GPIO value");
+
+ /* bus is not going up again, so we have an error */
+ if (val != 1)
+ return 1;
+
+ /* all good, presence detected */
+ return 0;
+}
+
+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)
+ 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),
+};
--
2.7.4