Hello! 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. Changes in v7: - rename mutex to rx_mutex and comment its usage - fix comments and use kerneldoc for internal structs - Link to v6: https://lore.kernel.org/r/20240209-w1-uart-v6-0-3e753c149196@xxxxxxxxx Thanks Krzysztof for the review. Changes in v6: - change order of patches for dt-binding - remove unnecessary lock in remove - delay for 1-Wire cycle without mutex lock - fix comment style and add some more comments - Link to v5: https://lore.kernel.org/r/20240126-w1-uart-v5-0-1d82bfdc2ae9@xxxxxxxxx Thanks Krzysztof and Rob for the review. Changes in v5: - dt-binding: allow child object for onewire and use prefix -bps for baud rate configuration. - use type u8 for a byte, instead of unsigned char - use constants (NSEC_PER_SEC, BITS_PER_BYTE) - make delay computation from packet time more coherent - Link to v4: https://lore.kernel.org/r/20240106-w1-uart-v4-0-7fe1378a8b3e@xxxxxxxxx Thanks Jiri, Krzysztof and Rob for the review. Changes in v4: - rework baud-rate configuration: also check max bit-time, support higher baud-rates by adding a delay to complete 1-Wire cycle. - dt-binding w1-uart: specify baud-rates for 1-Wire operations - Link to v3: https://lore.kernel.org/r/20240105-w1-uart-v3-0-8687093b2e76@xxxxxxxxx Changes in v3: - improve baud-rate configuration: use specific limits for 1-Wire reset, touch-0 and touch-1 operation, compute in nanoseconds. - remove unused header atomic.h - use function instead of macro to compute bit-time from baud-rate - switch to b4 util to publish patch: missing recipients - Link to v2: https://lore.kernel.org/lkml/20231223100408.44056-1-cj.winklhofer@xxxxxxxxx Changes in v2: - add documentation for dt-binding - allow onewire as serial child node - support different baud-rates: 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. - fix locking problem for serdev-receive and w1-master reset/touch: The received byte is now protected with a mutex - instead of the atomic, which was used before due to the concurrent store and load. - explicit error in serdev-receive: 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. - fix variable names, errno-returns, wrong define CONFIG_OF - fix log flooding - fix driver remove (error-path for rxtx-function) - Link to v1: https://lore.kernel.org/all/20231217122004.42795-1-cj.winklhofer@xxxxxxxxx Krzysztof, thank your very much for your feedback! 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 1-Wire - Patch 2: allow onewire as serial child node - Patch 3: 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 (3): dt-bindings: serial: allow onewire as child node dt-bindings: w1: UART 1-Wire bus w1: add UART w1 bus driver .../devicetree/bindings/serial/serial.yaml | 2 +- Documentation/devicetree/bindings/w1/w1-uart.yaml | 60 +++ Documentation/w1/masters/index.rst | 1 + Documentation/w1/masters/w1-uart.rst | 54 +++ drivers/w1/masters/Kconfig | 10 + drivers/w1/masters/Makefile | 1 + drivers/w1/masters/w1-uart.c | 415 +++++++++++++++++++++ 7 files changed, 542 insertions(+), 1 deletion(-) --- base-commit: 6613476e225e090cc9aad49be7fa504e290dd33d change-id: 20240104-w1-uart-ee8685a15a50 Best regards, -- Christoph Winklhofer <cj.winklhofer@xxxxxxxxx>
