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

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Date: Sat, 23 Dec 2023 10:54:47 +0100
From: Christoph Winklhofer <cj.winklhofer@...il.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc: robh+dt@...nel.org, conor+dt@...nel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 0/2] w1: add UART w1 bus driver

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@...il.com>'
> Grabbing thread from
> lore.kernel.org/all/20231221065049.30703-1-cj.winklhofer@...il.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