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https://github.com/AsahiLinux/u-boot
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73aea285e3
Add a bus driver for bitbanging a 1-Wire bus over a GPIO. Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com> [eugen.hristev@microchip.com: fixed some issues] Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
176 lines
3.8 KiB
C
176 lines
3.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0+
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*
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* Copyright (c) 2015 Free Electrons
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* Copyright (c) 2015 NextThing Co
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*
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* Maxime Ripard <maxime.ripard@free-electrons.com>
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*
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*/
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#include <common.h>
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#include <dm.h>
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#include <w1.h>
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#include <asm/gpio.h>
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#define W1_TIMING_A 6
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#define W1_TIMING_B 64
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#define W1_TIMING_C 60
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#define W1_TIMING_D 10
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#define W1_TIMING_E 9
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#define W1_TIMING_F 55
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#define W1_TIMING_G 0
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#define W1_TIMING_H 480
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#define W1_TIMING_I 70
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#define W1_TIMING_J 410
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struct w1_gpio_pdata {
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struct gpio_desc gpio;
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u64 search_id;
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};
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static bool w1_gpio_read_bit(struct udevice *dev)
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{
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struct w1_gpio_pdata *pdata = dev_get_platdata(dev);
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int val;
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dm_gpio_set_dir_flags(&pdata->gpio, GPIOD_IS_OUT);
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udelay(W1_TIMING_A);
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dm_gpio_set_dir_flags(&pdata->gpio, GPIOD_IS_IN);
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udelay(W1_TIMING_E);
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val = dm_gpio_get_value(&pdata->gpio);
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if (val < 0)
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debug("error in retrieving GPIO value");
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udelay(W1_TIMING_F);
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return val;
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}
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static u8 w1_gpio_read_byte(struct udevice *dev)
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{
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int i;
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u8 ret = 0;
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for (i = 0; i < 8; ++i)
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ret |= (w1_gpio_read_bit(dev) ? 1 : 0) << i;
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return ret;
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}
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static void w1_gpio_write_bit(struct udevice *dev, bool bit)
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{
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struct w1_gpio_pdata *pdata = dev_get_platdata(dev);
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dm_gpio_set_dir_flags(&pdata->gpio, GPIOD_IS_OUT);
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bit ? udelay(W1_TIMING_A) : udelay(W1_TIMING_C);
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dm_gpio_set_value(&pdata->gpio, 1);
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bit ? udelay(W1_TIMING_B) : udelay(W1_TIMING_D);
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}
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static void w1_gpio_write_byte(struct udevice *dev, u8 byte)
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{
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int i;
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for (i = 0; i < 8; ++i)
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w1_gpio_write_bit(dev, (byte >> i) & 0x1);
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}
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static bool w1_gpio_reset(struct udevice *dev)
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{
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struct w1_gpio_pdata *pdata = dev_get_platdata(dev);
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int val;
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/* initiate the reset pulse. first we must pull the bus to low */
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dm_gpio_set_dir_flags(&pdata->gpio, GPIOD_IS_OUT | GPIOD_IS_OUT_ACTIVE);
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udelay(W1_TIMING_G);
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dm_gpio_set_value(&pdata->gpio, 0);
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/* wait for the specified time with the bus kept low */
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udelay(W1_TIMING_H);
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/* now we must read the presence pulse */
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dm_gpio_set_dir_flags(&pdata->gpio, GPIOD_IS_IN);
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udelay(W1_TIMING_I);
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val = dm_gpio_get_value(&pdata->gpio);
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if (val < 0)
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debug("error in retrieving GPIO value");
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/* if nobody pulled the bus down , it means nobody is on the bus */
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if (val != 0)
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return 1;
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/* we have the bus pulled down, let's wait for the specified presence time */
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udelay(W1_TIMING_J);
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/* read again, the other end should leave the bus free */
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val = dm_gpio_get_value(&pdata->gpio);
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if (val < 0)
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debug("error in retrieving GPIO value");
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/* bus is not going up again, so we have an error */
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if (val != 1)
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return 1;
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/* all good, presence detected */
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return 0;
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}
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static u8 w1_gpio_triplet(struct udevice *dev, bool bdir)
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{
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u8 id_bit = w1_gpio_read_bit(dev);
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u8 comp_bit = w1_gpio_read_bit(dev);
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u8 retval;
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if (id_bit && comp_bit)
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return 0x03; /* error */
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if (!id_bit && !comp_bit) {
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/* Both bits are valid, take the direction given */
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retval = bdir ? 0x04 : 0;
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} else {
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/* Only one bit is valid, take that direction */
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bdir = id_bit;
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retval = id_bit ? 0x05 : 0x02;
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}
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w1_gpio_write_bit(dev, bdir);
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return retval;
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}
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static const struct w1_ops w1_gpio_ops = {
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.read_byte = w1_gpio_read_byte,
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.reset = w1_gpio_reset,
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.triplet = w1_gpio_triplet,
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.write_byte = w1_gpio_write_byte,
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};
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static int w1_gpio_ofdata_to_platdata(struct udevice *dev)
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{
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struct w1_gpio_pdata *pdata = dev_get_platdata(dev);
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int ret;
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ret = gpio_request_by_name(dev, "gpios", 0, &pdata->gpio, 0);
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if (ret < 0)
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printf("Error claiming GPIO %d\n", ret);
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return ret;
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};
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static const struct udevice_id w1_gpio_id[] = {
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{ "w1-gpio", 0 },
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{ },
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};
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U_BOOT_DRIVER(w1_gpio_drv) = {
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.id = UCLASS_W1,
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.name = "w1_gpio_drv",
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.of_match = w1_gpio_id,
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.ofdata_to_platdata = w1_gpio_ofdata_to_platdata,
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.ops = &w1_gpio_ops,
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.platdata_auto_alloc_size = sizeof(struct w1_gpio_pdata),
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};
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