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Fri, 26 Jan 2024 15:42:38 +0000 (UTC) From: Christoph Winklhofer via B4 Relay Subject: [PATCH v5 0/3] w1: add UART w1 bus driver Date: Fri, 26 Jan 2024 16:42:02 +0100 Message-Id: <20240126-w1-uart-v5-0-1d82bfdc2ae9@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-B4-Tracking: v=1; b=H4sIAMrSs2UC/02OzQ6CMBAGX8X07JLtH1RPvofxUHCRqlBTEDSEd 7eQqBz28CU7kxlZS8FRy/abkQXqXet8E4feblhR2eZC4M5xM4FCIUcFA4enDR0QmdRoy7XVyOL 3I1DpXovpeIq7DL6Grgpkv7zkIh6iQpMohToFDsU1GVxzu1e+pHC41Nbdk8LXs7BybefDeynr5 az9RuhfRC8BIXZkuJO5oCxdKeaIXq259M+pyGUlcZkZa3JJa26apg/1cHhQFwEAAA== To: Krzysztof Kozlowski , Rob Herring , Conor Dooley , Christoph Winklhofer , Rob Herring , Greg Kroah-Hartman , Jiri Slaby , Krzysztof Kozlowski , Jonathan Corbet Cc: devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, linux-doc@vger.kernel.org X-Mailer: b4 0.12.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1706283756; l=4786; i=cj.winklhofer@gmail.com; s=20240104; h=from:subject:message-id; bh=Y3Z8LYJk8ojW2lKAiG+yhwYm9jBbV1csLki0ZOFKhMU=; b=R7jPweL5XSb8Z6yp5Suh+YaLtVSrdR/qZScd1ek+b7zMEqmM4CViPNz9//ExzoN4cS/V1iWGN p22SMvhB6kFBdh3lKRlb1aK20ei243q+aWJr1N5gDMfxQrWPaE+ys/d X-Developer-Key: i=cj.winklhofer@gmail.com; a=ed25519; pk=lgjGjOt7hFKJT9UXhgUyrdthxvZ7DJ5F1U/7d9qdAsk= X-Endpoint-Received: by B4 Relay for cj.winklhofer@gmail.com/20240104 with auth_id=111 X-Original-From: Christoph Winklhofer Reply-To: 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 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@gmail.com 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@gmail.com 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@gmail.com 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@gmail.com 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: w1: UART 1-Wire bus dt-bindings: serial: allow onewire as child node 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 | 402 +++++++++++++++++++++ 7 files changed, 529 insertions(+), 1 deletion(-) --- base-commit: 6613476e225e090cc9aad49be7fa504e290dd33d change-id: 20240104-w1-uart-ee8685a15a50 Best regards, -- Christoph Winklhofer