Re: [PATCH v1 1/1] tpm: tis_i2c: Add reset delays for ST33KTPM2XI2C

[Jarkko Sakkinen <jarkko@kernel.org>]

On Wed, Oct 28, 2026 at 10:45:04AM +0100, Stefano Radaelli wrote:
> From: Stefano Radaelli <stefano.r@variscite.com>
> 
> The optional reset control is deasserted without a delay, and probe then
> proceeds directly to the first I2C register access. Since reset-gpio
> initializes its line asserted, this provides no guaranteed minimum reset
> pulse width or recovery interval before communication starts.
> 
> Table 66 of the ST33KTPM-IDevID datasheet specifies a minimum reset pulse
> width of 1 ms and up to 50 ms from reset release before the first command.
> Choose a 2 ms assertion interval to provide margin above the minimum and
> wait 50 ms after deassertion, before initializing the I2C guard times.
> 
> Associate these timings with the existing st,st33ktpm2xi2c compatible using
> match data. Apply the delays only when a reset control is present. Preserve
> the existing deassert-only sequence and the behavior of devices without
> timing data or a reset control, without adding Device Tree properties.

"Pull the timings from the matched device entry. If they don't exist,
fall back to the legacy behavior without delays. Update of_tis_i2c_match
with the timings for st33ktpm2xi2c."

I.e. the last paragraph has the language of a white paper.

Br, Jarkko