On 06. 01. 24, 17:02, Christoph Winklhofer via B4 Relay wrote:
From: Christoph Winklhofer <cj.winklhofer@xxxxxxxxx>
Add a UART 1-Wire bus driver. The driver utilizes the UART interface via
the Serial Device Bus to create the 1-Wire timing patterns. The driver
was tested on a "Raspberry Pi 3B" with a DS18B20 and on a "Variscite
DART-6UL" with a DS18S20 temperature sensor.
The 1-Wire timing pattern and the corresponding UART baud-rate with the
interpretation of the transferred bytes are described in the document:
Link: https://www.analog.com/en/technical-articles/using-a-uart-to-implement-a-1wire-bus-master.html
In short, the UART peripheral must support full-duplex and operate in
open-drain mode. The timing patterns are generated by a specific
combination of baud-rate and transmitted byte, which corresponds to a
1-Wire read bit, write bit or reset.
...
--- /dev/null
+++ b/drivers/w1/masters/w1-uart.c
@@ -0,0 +1,398 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * w1-uart - UART 1-Wire bus driver
+ *
+ * Uses the UART interface (via Serial Device Bus) to create the 1-Wire
+ * timing patterns. Implements the following 1-Wire master interface:
+ *
+ * - reset_bus: requests baud-rate 9600
+ *
+ * - touch_bit: requests baud-rate 115200
+ *
+ * Author: Christoph Winklhofer <cj.winklhofer@xxxxxxxxx>
+ */
+
+#include <linux/completion.h>
+#include <linux/delay.h>
+#include <linux/jiffies.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/serdev.h>
+#include <linux/w1.h>
+
+#define W1_UART_TIMEOUT msecs_to_jiffies(500)
+
+/*
+ * struct w1_uart_config - configuration for 1-Wire operation
+ *
+ * @baudrate: baud-rate returned from serdev
+ * @delay_us: delay to complete a 1-Wire cycle (in us)
+ * @tx_byte: byte to generate 1-Wire timing pattern
+ */
+struct w1_uart_config {
+ unsigned int baudrate;
+ unsigned int delay_us;
+ unsigned char tx_byte;
If it is a "byte", it should be u8.
+};
+
+struct w1_uart_device {
+ struct serdev_device *serdev;
+ struct w1_bus_master bus;
+
+ struct w1_uart_config cfg_reset;
+ struct w1_uart_config cfg_touch_0;
+ struct w1_uart_config cfg_touch_1;
+
+ struct completion rx_byte_received;
+ unsigned char rx_byte;
The same here.
+ int rx_err;
+
+ struct mutex mutex;
+};
+
+/*
+ * struct w1_uart_limits - limits for 1-Wire operations
+ *
+ * @baudrate: Requested baud-rate to create 1-Wire timing pattern
+ * @bit_min_us: minimum time for a bit (in us)
+ * @bit_max_us: maximum time for a bit (in us)
+ * @sample_us: timespan to sample 1-Wire response
+ * @cycle_us: duration of the 1-Wire cycle
+ */
+struct w1_uart_limits {
+ unsigned int baudrate;
+ unsigned int bit_min_us;
+ unsigned int bit_max_us;
+ unsigned int sample_us;
+ unsigned int cycle_us;
+};
+
+static inline unsigned int baud_to_bit_ns(unsigned int baud)
+{
+ return 1000000000 / baud;
NSEC_PER_SEC
+}
+
+static inline unsigned int to_ns(unsigned int us)
+{
+ return us * 1000;
NSEC_PER_USEC
+}
+
+/*
+ * Set baud-rate, delay and tx-byte to create a 1-Wire pulse and adapt
+ * the tx-byte according to the actual baud-rate.
+ *
+ * Reject when:
+ * - time for a bit outside min/max range
+ * - a 1-Wire response is not detectable for sent byte
+ */
+static int w1_uart_set_config(struct serdev_device *serdev,
+ const struct w1_uart_limits *limits,
+ struct w1_uart_config *w1cfg)
+{
+ unsigned int bits_low;
+ unsigned int bit_ns;
+ unsigned int low_ns;
+
+ w1cfg->baudrate = serdev_device_set_baudrate(serdev, limits->baudrate);
+ if (w1cfg->baudrate == 0)
+ return -EINVAL;
+
+ /* Compute in nanoseconds for accuracy */
+ bit_ns = baud_to_bit_ns(w1cfg->baudrate);
+ bits_low = to_ns(limits->bit_min_us) / bit_ns;
+ /* start bit is always low */
+ low_ns = bit_ns * (bits_low + 1);
+
+ if (low_ns < to_ns(limits->bit_min_us))
+ return -EINVAL;
+
+ if (low_ns > to_ns(limits->bit_max_us))
+ return -EINVAL;
+
+ /* 1-Wire response detectable for sent byte */
+ if (limits->sample_us > 0 &&
+ bit_ns * 8 < low_ns + to_ns(limits->sample_us))
BITS_PER_BYTE
+ return -EINVAL;
+
+ /* delay to complete 1-Wire cycle, include start and stop-bit */
+ w1cfg->delay_us = 0;
+ if (bit_ns * 10 < to_ns(limits->cycle_us))
What is this 10? Dub it.
+ w1cfg->delay_us =
+ (to_ns(limits->cycle_us) - bit_ns * 10) / 1000;
And this 10?
The end: / NSEC_PER_USEC
+
+ /* byte to create 1-Wire pulse */
+ w1cfg->tx_byte = 0xff << bits_low;
+
+ return 0;
+}
...
+static int w1_uart_serdev_tx_rx(struct w1_uart_device *w1dev,
+ const struct w1_uart_config *w1cfg,
+ unsigned char *rx_byte)
u8 *
+{
...
+}
+
+static int w1_uart_serdev_receive_buf(struct serdev_device *serdev,
+ const unsigned char *buf, size_t count)
serdev already uses u8 * here. You are basing on the top of some old tree.
regards,
--
js
suse labs
