netdev - Re: [PATCH v1 00/15] create power sequencing subsystem

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Date:   Wed, 1 Mar 2023 10:02:48 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Alexander Stein <alexander.stein@...tq-group.com>
Cc:     Matthias Kaehlcke <mka@...omium.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Stanimir Varbanov <svarbanov@...sol.com>,
        linux-arm-msm@...r.kernel.org, linux-mmc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-bluetooth@...r.kernel.org,
        ath10k@...ts.infradead.org, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH v1 00/15] create power sequencing subsystem

On Wed, 1 Mar 2023 at 09:17, Alexander Stein
<alexander.stein@...tq-group.com> wrote:
>
> Hi,
>
> sorry for being late to the party.
>
> Am Mittwoch, 19. Oktober 2022, 08:03:22 CET schrieb Dmitry Baryshkov:
> > Ho,
> >
> > On Thu, 13 Oct 2022 at 22:50, Matthias Kaehlcke <mka@...omium.org> wrote:
> > > Do you still plan to refresh this series?
> > >
> > > I know there have been multiple attempts to get something similar
> > > landed in the past 10 year or so. Your series didn't seem to get
> > > much pushback from maintainers, might be worth sending a refresh :)
> >
> > Yes, I hope to return to it eventually. I just had no time for it lately.
>
> I just found this thread while searching for power sequencing devices in
> Linux. From what I understand this is transforming the existing mmc pwrseq
> drivers into generic ones. What is the intention of this new subsystem? What
> is it supposed to address?
> In my case I have an LTE module attached via USB, but in order to use it I
> need to perform several steps:
> 1. apply power supply
> 2. Issue a reset pulse(!), the length actually defines whether its a reset or
> poweroff/on
> 3a. wait for a GPIO to toggle
> 3b. wait a minimum time
> 4a. device will enumerate on USB
> 4b. device can be access using UART
>
> This is something required to actually see/detect the device in the first
> place, thus it cannot be part of the device driver side.
> Is this something pwrseq is supposed to address?

Yes, this is one of those typical use-cases for discoverable buses
that we need to add support for, in one way or the other.

>
> Best regards,
> Alexander

[...]

Kind regards
Uffe