[PATCH v1 0/2] w1: add UART w1 bus driver

[PATCH v1 0/2] w1: add UART w1 bus driver

[Christoph Winklhofer]

Hello!

Krzysztof, thank your very much for your feedback!

This patch contains a driver for a 1-Wire bus over UART. The driver
utilizes the UART interface via the Serial Device Bus to create the
1-Wire timing patterns.

Version 1

- In v1, the driver requests a baud-rate (9600 for reset and 115200 for
write/read) and tries to adapt the transmitted byte according to the
actual baud-rate returned from serdev. Is this the correct direction or
should the baud-rate be specified in the device-tree? Alternatively,
it could make sense to specify the minimum and maximum times for the
1-Wire operations in the device-tree, instead of using hard-coded ones
similar as in "Figure 11. Configuration tab" of the linked document
"Using UART to Implement a 1-Wire Bus Master".

- In addition, the received byte is now protected with a mutex - instead
of the atomic, which I used before due to the concurrent store and load.

- Receiving more than one byte results in an error, since the w1-uart
driver is the only writer, it writes a single-byte and should receive
a single byte.

Changes:
- support different baud-rates
- fix variable names, errno-returns, wrong define CONFIG_OF
- fix log flooding
- fix locking problem for serdev-receive and w1-master reset/touch
- fix driver remove (error-path for rxtx-function)
- add documentation for dt-binding


It was tested on a "Raspberry Pi 3 Model B+" with a DS18B20 and on a
"Variscite DART-6UL" with a DS18S20 temperature sensor.

Content:
- Patch 1: device tree binding
- Patch 2: driver and documentation

The patch was created against the w1 subsytem tree (branch w1-next):
  Link: https://git.kernel.org/pub/scm/linux/kernel/git/krzk/linux-w1.git/

The checkpatch.pl script reported the following error - which I am not
sure how to fix:
  WARNING: added, moved or deleted file(s), does MAINTAINERS need
  updating?

The technical details for 1-Wire over UART are 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 pulse.

For instance the timing pattern for a 1-Wire reset and presence detect
uses the baud-rate 9600, i.e. 104.2 us per bit. The transmitted byte
0xf0 over UART (least significant bit first, start-bit low) sets the
reset low time for 1-Wire to 521 us. A present 1-Wire device changes the
received byte by pulling the line low, which is used by the driver to
evaluate the result of the 1-Wire operation.

Similar for a 1-Wire read bit or write bit, which uses the baud-rate
115200, i.e. 8.7 us per bit. The transmitted byte 0x00 is used for a
Write-0 operation and the byte 0xff for Read-0, Read-1 and Write-1.

Hope the driver is helpful.

Thanks,
Christoph

Christoph Winklhofer (2):
  dt-bindings: w1: UART 1-wire bus
  w1: add UART w1 bus driver

 .../devicetree/bindings/w1/w1-uart.yaml       |  44 +++
 Documentation/w1/masters/index.rst            |   1 +
 Documentation/w1/masters/w1-uart.rst          |  53 +++
 drivers/w1/masters/Kconfig                    |  10 +
 drivers/w1/masters/Makefile                   |   1 +
 drivers/w1/masters/w1-uart.c                  | 307 ++++++++++++++++++
 6 files changed, 416 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/w1/w1-uart.yaml
 create mode 100644 Documentation/w1/masters/w1-uart.rst
 create mode 100644 drivers/w1/masters/w1-uart.c


base-commit: efc19c44aa442197ddcbb157c6ca54a56eba8c4e
-- 
2.43.0

[PATCH v1 1/2] dt-bindings: w1: UART 1-wire bus

[Christoph Winklhofer]

Add device tree binding for UART 1-wire bus.

Signed-off-by: Christoph Winklhofer <cj.winklhofer@gmail.com>
---
 .../devicetree/bindings/w1/w1-uart.yaml       | 44 +++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/w1/w1-uart.yaml

diff --git a/Documentation/devicetree/bindings/w1/w1-uart.yaml b/Documentation/devicetree/bindings/w1/w1-uart.yaml
new file mode 100644
index 000000000000..93d83c42c407
--- /dev/null
+++ b/Documentation/devicetree/bindings/w1/w1-uart.yaml
@@ -0,0 +1,44 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/w1/w1-uart.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: UART 1-Wire Bus
+
+maintainers:
+  - Christoph Winklhofer <cj.winklhofer@gmail.com>
+
+description: |
+  UART 1-wire bus. Utilizes the UART interface via the Serial Device Bus
+  to create the 1-Wire timing patterns.
+
+  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 pulse.
+
+  The default baud-rate for reset and presence detection is 9600 and for
+  a 1-Wire read or write operation 115200. In case the actual baud-rate
+  is different from the requested one, the transmitted byte is adapted
+  to generate the 1-Wire timing patterns.
+
+  https://www.analog.com/en/technical-articles/using-a-uart-to-implement-a-1wire-bus-master.html
+
+
+properties:
+  compatible:
+    const: w1-uart
+
+required:
+  - compatible
+
+additionalProperties: false
+
+examples:
+  - |
+    serial {
+      onewire {
+        compatible = "w1-uart";
+      };
+    };
-- 
2.43.0

[PATCH v1 2/2] w1: add UART w1 bus driver

[Christoph Winklhofer]

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.

Signed-off-by: Christoph Winklhofer <cj.winklhofer@gmail.com>
---
 Documentation/w1/masters/index.rst   |   1 +
 Documentation/w1/masters/w1-uart.rst |  53 +++++
 drivers/w1/masters/Kconfig           |  10 +
 drivers/w1/masters/Makefile          |   1 +
 drivers/w1/masters/w1-uart.c         | 307 +++++++++++++++++++++++++++
 5 files changed, 372 insertions(+)
 create mode 100644 Documentation/w1/masters/w1-uart.rst
 create mode 100644 drivers/w1/masters/w1-uart.c

diff --git a/Documentation/w1/masters/index.rst b/Documentation/w1/masters/index.rst
index 4442a98850ad..cc40189909fd 100644
--- a/Documentation/w1/masters/index.rst
+++ b/Documentation/w1/masters/index.rst
@@ -12,3 +12,4 @@
    mxc-w1
    omap-hdq
    w1-gpio
+   w1-uart
diff --git a/Documentation/w1/masters/w1-uart.rst b/Documentation/w1/masters/w1-uart.rst
new file mode 100644
index 000000000000..a5a097886f8a
--- /dev/null
+++ b/Documentation/w1/masters/w1-uart.rst
@@ -0,0 +1,53 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+=====================
+Kernel driver w1-uart
+=====================
+
+Author: Christoph Winklhofer <cj.winklhofer@gmail.com>
+
+
+Description
+-----------
+
+UART 1-wire bus driver. The driver utilizes the UART interface via the
+Serial Device Bus to create the 1-Wire timing patterns as described in
+the document `"Using a UART to Implement a 1-Wire Bus Master"`_.
+
+.. _"Using a UART to Implement a 1-Wire Bus Master": 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 pulse.
+
+For instance the timing pattern for a 1-Wire reset and presence detect uses
+the baud-rate 9600, i.e. 104.2 us per bit. The transmitted byte 0xf0 over
+UART (least significant bit first, start-bit low) sets the reset low time
+for 1-Wire to 521 us. A present 1-Wire device changes the received byte by
+pulling the line low, which is used by the driver to evaluate the result of
+the 1-Wire operation.
+
+Similar for a 1-Wire read bit or write bit, which uses the baud-rate
+115200, i.e. 8.7 us per bit. The transmitted byte 0x00 is used for a
+Write-0 operation and the byte 0xff for Read-0, Read-1 and Write-1.
+
+The default baud-rate for reset and presence detection is 9600 and for
+a 1-Wire read or write operation 115200. In case the actual baud-rate
+is different from the requested one, the transmitted byte is adapted
+to generate the 1-Wire timing patterns.
+
+
+Usage
+-----
+
+Specify the UART 1-wire bus in the device tree by adding the single child
+onewire to the serial node (e.g. uart0). For example:
+::
+
+  @uart0 {
+    ...
+    onewire {
+      compatible = "w1-uart";
+    };
+  };
diff --git a/drivers/w1/masters/Kconfig b/drivers/w1/masters/Kconfig
index 513c0b114337..e6049a75b35b 100644
--- a/drivers/w1/masters/Kconfig
+++ b/drivers/w1/masters/Kconfig
@@ -78,5 +78,15 @@ config W1_MASTER_SGI
 	  This support is also available as a module.  If so, the module
 	  will be called sgi_w1.
 
+config W1_MASTER_UART
+	tristate "UART 1-wire driver"
+	depends on SERIAL_DEV_BUS
+	help
+	  Say Y here if you want to communicate with your 1-wire devices using
+	  UART interface.
+
+	  This support is also available as a module.  If so, the module
+	  will be called w1-uart.
+
 endmenu
 
diff --git a/drivers/w1/masters/Makefile b/drivers/w1/masters/Makefile
index 6c5a21f9b88c..227f80987e69 100644
--- a/drivers/w1/masters/Makefile
+++ b/drivers/w1/masters/Makefile
@@ -12,3 +12,4 @@ obj-$(CONFIG_W1_MASTER_MXC)		+= mxc_w1.o
 obj-$(CONFIG_W1_MASTER_GPIO)		+= w1-gpio.o
 obj-$(CONFIG_HDQ_MASTER_OMAP)		+= omap_hdq.o
 obj-$(CONFIG_W1_MASTER_SGI)		+= sgi_w1.o
+obj-$(CONFIG_W1_MASTER_UART)		+= w1-uart.o
diff --git a/drivers/w1/masters/w1-uart.c b/drivers/w1/masters/w1-uart.c
new file mode 100644
index 000000000000..e195db3e9d9a
--- /dev/null
+++ b/drivers/w1/masters/w1-uart.c
@@ -0,0 +1,307 @@
+// 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@gmail.com>
+ */
+
+#include <linux/atomic.h>
+#include <linux/completion.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)
+
+#define baud_to_bit_us(baud) (1000000 / baud)
+
+struct w1_uart_device {
+	struct serdev_device *serdev;
+	struct w1_bus_master bus;
+
+	unsigned int baud_reset;
+	unsigned char tx_reset;
+
+	unsigned int baud_touch;
+	unsigned char tx_touch;
+
+	struct completion rx_byte_received;
+	unsigned char rx_byte;
+	int rx_err;
+
+	struct mutex mutex;
+};
+
+/*
+ * Set baud-rate and tx-byte for 1-wire reset and presence detect and
+ * adapt the tx-byte according to the actual baud-rate.
+ *
+ * Minimum reset low time is 480us and the response from a 1-Wire
+ * device is at around 570us. Reject when a bit takes longer than
+ * 500us or is to short to detect a manipulated byte.
+ *
+ */
+static int w1_uart_set_baud_reset(struct w1_uart_device *w1dev)
+{
+	struct serdev_device *serdev = w1dev->serdev;
+	unsigned int bit_us;
+	unsigned int bits_low;
+
+	w1dev->baud_reset = serdev_device_set_baudrate(serdev, 9600);
+	if (w1dev->baud_reset == 0)
+		return -EINVAL;
+
+	bit_us = baud_to_bit_us(w1dev->baud_reset);
+
+	/* reset low time is 480us */
+	if (bit_us > 500)
+		return -EINVAL;
+
+	/* At least Bit-8 should be manipulated by a present device,
+	 * which is at 570us. Bit-8 and start-bit: 9 * 65us
+	 */
+	if (bit_us < 65)
+		return -EINVAL;
+
+	/* byte to create reset pulse (start-bit is low) */
+	bits_low = 500 / bit_us;
+	w1dev->tx_reset = 0xff << bits_low;
+
+	return 0;
+}
+
+/*
+ * Set baud-rate and tx-byte for 1-Wire read and write cycle and
+ * adapt the tx-byte according to the actual baud-rate.
+ *
+ * Recommended low-time to initiate a Write-1 or Read is 6us. Time-slot
+ * for 1-Wire bit operation is 70us. Reject when a bit takes longer
+ * than 10us (recommended 6us) or the entire time-slot is to short.
+ */
+static int w1_uart_set_baud_touch(struct w1_uart_device *w1dev)
+{
+	struct serdev_device *serdev = w1dev->serdev;
+	unsigned int bits_low;
+	unsigned int bit_us;
+
+	w1dev->baud_touch = serdev_device_set_baudrate(serdev, 115200);
+	if (w1dev->baud_touch == 0)
+		return -EINVAL;
+
+	bit_us = baud_to_bit_us(w1dev->baud_touch);
+	/* low-time to start write-1 and read cycle */
+	if (bit_us > 10)
+		return -EINVAL;
+	/* 1-Wire time slot is 70 us */
+	if (bit_us < 7)
+		return -EINVAL;
+
+	/* max low time 10us */
+	bits_low = 5 / bit_us;
+	w1dev->tx_touch = 0xff << bits_low;
+
+	return 0;
+}
+
+static int w1_uart_serdev_open(struct w1_uart_device *w1dev)
+{
+	struct serdev_device *serdev = w1dev->serdev;
+	struct device *dev = &serdev->dev;
+	int ret;
+
+	ret = devm_serdev_device_open(dev, serdev);
+	if (ret < 0)
+		return ret;
+
+	ret = serdev_device_set_parity(serdev, SERDEV_PARITY_NONE);
+	if (ret < 0) {
+		dev_err(dev, "set parity failed\n");
+		return ret;
+	}
+
+	ret = w1_uart_set_baud_reset(w1dev);
+	if (ret < 0) {
+		dev_err(dev, "set baud-rate for reset failed\n");
+		return ret;
+	}
+
+	ret = w1_uart_set_baud_touch(w1dev);
+	if (ret < 0) {
+		dev_err(dev, "set baud-rate for touch failed\n");
+		return ret;
+	}
+
+	serdev_device_set_flow_control(serdev, false);
+
+	return 0;
+}
+
+/*
+ * Send one byte (tx_byte) and read one byte (rx_byte) via serdev.
+ */
+static int w1_uart_serdev_tx_rx(struct w1_uart_device *w1dev,
+				unsigned int baudrate, unsigned char tx_byte,
+				unsigned char *rx_byte)
+{
+	struct serdev_device *serdev = w1dev->serdev;
+	int ret;
+
+	serdev_device_write_flush(serdev);
+	serdev_device_set_baudrate(serdev, baudrate);
+
+	/* write and immediately read one byte */
+	reinit_completion(&w1dev->rx_byte_received);
+	ret = serdev_device_write_buf(serdev, &tx_byte, 1);
+	if (ret != 1)
+		return -EIO;
+	ret = wait_for_completion_interruptible_timeout(
+		&w1dev->rx_byte_received, W1_UART_TIMEOUT);
+	if (ret <= 0)
+		return -EIO;
+
+	/* locking could fail during driver remove or when serdev
+	 * is unexpectedly in the receive callback.
+	 */
+	if (!mutex_trylock(&w1dev->mutex))
+		return -EIO;
+
+	ret = w1dev->rx_err;
+	if (ret == 0)
+		*rx_byte = w1dev->rx_byte;
+
+	mutex_unlock(&w1dev->mutex);
+
+	return ret;
+}
+
+static int w1_uart_serdev_receive_buf(struct serdev_device *serdev,
+				      const unsigned char *buf, size_t count)
+{
+	struct w1_uart_device *w1dev = serdev_device_get_drvdata(serdev);
+
+	mutex_lock(&w1dev->mutex);
+
+	/* sent a single byte and receive one single byte */
+	if (count == 1) {
+		w1dev->rx_byte = buf[0];
+		w1dev->rx_err = 0;
+	} else {
+		w1dev->rx_err = -EIO;
+	}
+
+	mutex_unlock(&w1dev->mutex);
+	complete(&w1dev->rx_byte_received);
+
+	return count;
+}
+
+static const struct serdev_device_ops w1_uart_serdev_ops = {
+	.receive_buf = w1_uart_serdev_receive_buf,
+	.write_wakeup = serdev_device_write_wakeup,
+};
+
+/*
+ * 1-wire reset and presence detect: A present slave will manipulate
+ * the received byte by pulling the 1-wire low.
+ */
+static u8 w1_uart_reset_bus(void *data)
+{
+	struct w1_uart_device *w1dev = data;
+	unsigned char val;
+	int ret;
+
+	ret = w1_uart_serdev_tx_rx(w1dev, w1dev->baud_reset, w1dev->tx_reset,
+				   &val);
+	if (ret < 0)
+		return -1;
+
+	/* Device present (0) or no device (1) */
+	return val != w1dev->tx_reset ? 0 : 1;
+}
+
+/*
+ * 1-Wire read and write cycle: Only the Read-0 manipulates the
+ * received byte, all others left the line untouched.
+ */
+static u8 w1_uart_touch_bit(void *data, u8 bit)
+{
+	struct w1_uart_device *w1dev = data;
+	unsigned char val;
+	int ret;
+
+	ret = w1_uart_serdev_tx_rx(w1dev, w1dev->baud_touch,
+				   bit ? w1dev->tx_touch : 0x00, &val);
+	/* return inactive bus state on error */
+	if (ret < 0)
+		return 1;
+
+	return val == w1dev->tx_touch ? 1 : 0;
+}
+
+static int w1_uart_probe(struct serdev_device *serdev)
+{
+	struct device *dev = &serdev->dev;
+	struct w1_uart_device *w1dev;
+	int ret;
+
+	w1dev = devm_kzalloc(dev, sizeof(*w1dev), GFP_KERNEL);
+	if (!w1dev)
+		return -ENOMEM;
+	w1dev->bus.data = w1dev;
+	w1dev->bus.reset_bus = w1_uart_reset_bus;
+	w1dev->bus.touch_bit = w1_uart_touch_bit;
+	w1dev->serdev = serdev;
+
+	init_completion(&w1dev->rx_byte_received);
+	mutex_init(&w1dev->mutex);
+
+	ret = w1_uart_serdev_open(w1dev);
+	if (ret < 0)
+		return ret;
+	serdev_device_set_drvdata(serdev, w1dev);
+	serdev_device_set_client_ops(serdev, &w1_uart_serdev_ops);
+
+	return w1_add_master_device(&w1dev->bus);
+}
+
+static void w1_uart_remove(struct serdev_device *serdev)
+{
+	struct w1_uart_device *w1dev = serdev_device_get_drvdata(serdev);
+
+	mutex_lock(&w1dev->mutex);
+
+	w1_remove_master_device(&w1dev->bus);
+
+	mutex_unlock(&w1dev->mutex);
+}
+
+static const struct of_device_id w1_uart_of_match[] = {
+	{ .compatible = "w1-uart" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, w1_uart_of_match);
+
+static struct serdev_device_driver w1_uart_driver = {
+	.driver	= {
+		.name		= "w1-uart",
+		.of_match_table = w1_uart_of_match,
+	},
+	.probe	= w1_uart_probe,
+	.remove	= w1_uart_remove,
+};
+
+module_serdev_device_driver(w1_uart_driver);
+
+MODULE_DESCRIPTION("UART w1 bus driver");
+MODULE_AUTHOR("Christoph Winklhofer <cj.winklhofer@gmail.com>");
+MODULE_LICENSE("GPL");
-- 
2.43.0

Re: [PATCH v1 1/2] dt-bindings: w1: UART 1-wire bus

[Rob Herring]

On Thu, Dec 21, 2023 at 07:50:47AM +0100, Christoph Winklhofer wrote:
> Add device tree binding for UART 1-wire bus.
> 
> Signed-off-by: Christoph Winklhofer <cj.winklhofer@gmail.com>
> ---
>  .../devicetree/bindings/w1/w1-uart.yaml       | 44 +++++++++++++++++++
>  1 file changed, 44 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/w1/w1-uart.yaml
> 
> diff --git a/Documentation/devicetree/bindings/w1/w1-uart.yaml b/Documentation/devicetree/bindings/w1/w1-uart.yaml
> new file mode 100644
> index 000000000000..93d83c42c407
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/w1/w1-uart.yaml
> @@ -0,0 +1,44 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/w1/w1-uart.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: UART 1-Wire Bus
> +
> +maintainers:
> +  - Christoph Winklhofer <cj.winklhofer@gmail.com>
> +
> +description: |
> +  UART 1-wire bus. Utilizes the UART interface via the Serial Device Bus
> +  to create the 1-Wire timing patterns.
> +
> +  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 pulse.
> +
> +  The default baud-rate for reset and presence detection is 9600 and for
> +  a 1-Wire read or write operation 115200. In case the actual baud-rate
> +  is different from the requested one, the transmitted byte is adapted
> +  to generate the 1-Wire timing patterns.
> +
> +  https://www.analog.com/en/technical-articles/using-a-uart-to-implement-a-1wire-bus-master.html
> +
> +
> +properties:
> +  compatible:
> +    const: w1-uart
> +
> +required:
> +  - compatible
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    serial {
> +      onewire {

Have you tried this in an actual DT? Assuming the UART node has a 
schema, it should be a warning because child node names are explicit in 
serial.yaml unfortunately. IOW, you need to add "onewire" to 
serial.yaml.


> +        compatible = "w1-uart";
> +      };
> +    };
> -- 
> 2.43.0
> 

Re: [PATCH v1 0/2] w1: add UART w1 bus driver

[Krzysztof Kozlowski]

On 21/12/2023 07:50, Christoph Winklhofer wrote:
> Hello!
> 
> Krzysztof, thank your very much for your feedback!
> 
> This patch contains a driver for a 1-Wire bus over UART. The driver
> utilizes the UART interface via the Serial Device Bus to create the
> 1-Wire timing patterns.
> 
> Version 1
> 

You already sent v1, so this is v2:

b4 diff '<20231221065049.30703-1-cj.winklhofer@gmail.com>'
Grabbing thread from
lore.kernel.org/all/20231221065049.30703-1-cj.winklhofer@gmail.com/t.mbox.gz
---
Analyzing 4 messages in the thread
ERROR: Could not auto-find previous revision
       Run "b4 am -T" manually, then "b4 diff -m mbx1 mbx2"

I still cannot find the changelog. Does it mean nothing improved?


> - In v1, the driver requests a baud-rate (9600 for reset and 115200 for
> write/read) and tries to adapt the transmitted byte according to the
> actual baud-rate returned from serdev. Is this the correct direction or
> should the baud-rate be specified in the device-tree? Alternatively,
> it could make sense to specify the minimum and maximum times for the
> 1-Wire operations in the device-tree, instead of using hard-coded ones
> similar as in "Figure 11. Configuration tab" of the linked document
> "Using UART to Implement a 1-Wire Bus Master".

Depends, are these hardware properties? Are these runtime? What do they
depend on?

> 
> - In addition, the received byte is now protected with a mutex - instead
> of the atomic, which I used before due to the concurrent store and load.
> 
> - Receiving more than one byte results in an error, since the w1-uart
> driver is the only writer, it writes a single-byte and should receive
> a single byte.
> 
> Changes:
> - support different baud-rates
> - fix variable names, errno-returns, wrong define CONFIG_OF
> - fix log flooding
> - fix locking problem for serdev-receive and w1-master reset/touch
> - fix driver remove (error-path for rxtx-function)
> - add documentation for dt-binding

So this looks like changelog. Please make it explicit - move it to the
beginning of cover letter and say "changes in v2".


Best regards,
Krzysztof

Re: [PATCH v1 1/2] dt-bindings: w1: UART 1-wire bus

[Christoph Winklhofer]

On Thu, Dec 21, 2023 at 02:59:58PM -0600, Rob Herring wrote:
> On Thu, Dec 21, 2023 at 07:50:47AM +0100, Christoph Winklhofer wrote:
> > Add device tree binding for UART 1-wire bus.
> > 
> > Signed-off-by: Christoph Winklhofer <cj.winklhofer@gmail.com>
> > ---
> >  .../devicetree/bindings/w1/w1-uart.yaml       | 44 +++++++++++++++++++
> >  1 file changed, 44 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/w1/w1-uart.yaml
> > 
> > diff --git a/Documentation/devicetree/bindings/w1/w1-uart.yaml b/Documentation/devicetree/bindings/w1/w1-uart.yaml
> > new file mode 100644
> > index 000000000000..93d83c42c407
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/w1/w1-uart.yaml
> > @@ -0,0 +1,44 @@
> > +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/w1/w1-uart.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: UART 1-Wire Bus
> > +
> > +maintainers:
> > +  - Christoph Winklhofer <cj.winklhofer@gmail.com>
> > +
> > +description: |
> > +  UART 1-wire bus. Utilizes the UART interface via the Serial Device Bus
> > +  to create the 1-Wire timing patterns.
> > +
> > +  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 pulse.
> > +
> > +  The default baud-rate for reset and presence detection is 9600 and for
> > +  a 1-Wire read or write operation 115200. In case the actual baud-rate
> > +  is different from the requested one, the transmitted byte is adapted
> > +  to generate the 1-Wire timing patterns.
> > +
> > +  https://www.analog.com/en/technical-articles/using-a-uart-to-implement-a-1wire-bus-master.html
> > +
> > +
> > +properties:
> > +  compatible:
> > +    const: w1-uart
> > +
> > +required:
> > +  - compatible
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    serial {
> > +      onewire {
> 
> Have you tried this in an actual DT? Assuming the UART node has a 
> schema, it should be a warning because child node names are explicit in 
> serial.yaml unfortunately. IOW, you need to add "onewire" to 
> serial.yaml.
>

Thank you! It was tested on an older DT with the wildcard pattern. I
updated my test-system and now get the warning. On the Raspberry PI, 
a DT overlay was used, in this case there is no warning with:

  make CHECK_DTBS=y overlays/w1-uart.dtbo ARCH=arm

Is it possible to do a validation for a DT overlay? Since the overlay
may be incomplete, only existing nodes or properties could be checked.

Thanks!
Christoph

Re: [PATCH v1 0/2] w1: add UART w1 bus driver

[Christoph Winklhofer]

On Thu, Dec 21, 2023 at 10:13:01PM +0100, Krzysztof Kozlowski wrote:
> On 21/12/2023 07:50, Christoph Winklhofer wrote:
> > Hello!
> > 
> > Krzysztof, thank your very much for your feedback!
> > 
> > This patch contains a driver for a 1-Wire bus over UART. The driver
> > utilizes the UART interface via the Serial Device Bus to create the
> > 1-Wire timing patterns.
> > 
> > Version 1
> > 
> 
> You already sent v1, so this is v2:
> 
> b4 diff '<20231221065049.30703-1-cj.winklhofer@gmail.com>'
> Grabbing thread from
> lore.kernel.org/all/20231221065049.30703-1-cj.winklhofer@gmail.com/t.mbox.gz
> ---
> Analyzing 4 messages in the thread
> ERROR: Could not auto-find previous revision
>        Run "b4 am -T" manually, then "b4 diff -m mbx1 mbx2"
> 
> I still cannot find the changelog. Does it mean nothing improved?
> 
> 

Sorry, I will fix the patch and resend it.

> > - In v1, the driver requests a baud-rate (9600 for reset and 115200 for
> > write/read) and tries to adapt the transmitted byte according to the
> > actual baud-rate returned from serdev. Is this the correct direction or
> > should the baud-rate be specified in the device-tree? Alternatively,
> > it could make sense to specify the minimum and maximum times for the
> > 1-Wire operations in the device-tree, instead of using hard-coded ones
> > similar as in "Figure 11. Configuration tab" of the linked document
> > "Using UART to Implement a 1-Wire Bus Master".
> 
> Depends, are these hardware properties? Are these runtime? What do they
> depend on?
> 

Ok, the timing constraints came from the 1-Wire protocol, so DT makes no
sense. Probably it would be nice to tweak them for different 1-Wire slaves
via parameter to the driver - however, I will left them hardcoded for now.

Thanks!
Christoph