From: Michael Shen <gpgpgp@google.com>
To: Ed Tanous <edtanous@google.com>
Cc: openbmc@lists.ozlabs.org, Benjamin Fair <benjaminfair@google.com>
Subject: Re: Propose a new application for reading DIMM SPD directly
Date: Fri, 11 Feb 2022 08:40:22 +0800 [thread overview]
Message-ID: <CAD1rtg8vM-2PckG1Cct7m5tyFJ-axvKQ_ky2z=rzV4O9mZjoWA@mail.gmail.com> (raw)
In-Reply-To: <CAH2-KxA6MhNXUs+KXAjHTcJe1gWyGwfL+OUQBuCfQnPMSX7GZQ@mail.gmail.com>
On Thu, Feb 10, 2022 at 6:45 AM Ed Tanous <edtanous@google.com> wrote:
>
> On Wed, Feb 9, 2022 at 1:14 PM Patrick Williams <patrick@stwcx.xyz> wrote:
> >
> > On Wed, Feb 09, 2022 at 12:20:00PM -0800, Ed Tanous wrote:
> > > On Wed, Feb 9, 2022 at 11:56 AM Patrick Williams <patrick@stwcx.xyz> wrote:
> > > > On Tue, Feb 08, 2022 at 04:23:12PM +0800, Michael Shen wrote:
> > > > > On Tue, Feb 8, 2022 at 3:11 PM Patrick Williams <patrick@stwcx.xyz> wrote:
> > > > > > On Tue, Feb 08, 2022 at 01:10:37PM +0800, Michael Shen wrote:
> >
> > > > > BIOS owns the MUX select pin and it can decide who owns the SPD(I2C/I3C) bus.
> > > > > From my understanding, BIOS only needs to read SPD during the POST stage.
> > > > > For the rest of time, BIOS will hand over the SPD bus to BMC.
> > > >
> > > > That seems like it might work. You'll have to deal with the time when the BIOS
> > > > has the mux in the BMC code somehow. Ideally I'd ask for the mux select to also
> > > > be fed to the BMC as an input GPIO so that you can differentiate between "we
> > > > don't own the mux" and "all the devices are NAKing us".
> > >
> > > This seems like a nitty gritty design detail that's best handled in
> > > code when we review it. I think the important bit here is that there
> > > are paths where this could work without a significant design issue.
> >
> > Just one subtlety. I wouldn't expect this, necessarily, to be in _our_ design
> > and/or code, except that we'd want to document the GPIO line like we do all
> > others. I was trying to hint that "if I were involved in this hardware design,
> > I'd ask for...". If you leave it out, I'm sure it'll work _most_ of the time
> > just fine and it'll be your problem to debug it when it doesn't.
>
> Understood.
Thanks for all your suggestions. I will keep them in mind during implementation.
> > > > You should take a look at what is already existing in fru-device (part of
> > > > entity-manager repository). This is already doing this for IPMI-format EEPROM
> > > > data. We should be able to replicate/enhance this code, in the same repository,
> > > > to handle SPD format.
> > >
> > > I am not sure if it's a good idea to put it into the entity-manager
> > > repo. As you said EM
> > > is designed for IPMI-format EEPROM. Adding another parser into that
> > > repo may violate
> > > EM's design.
> >
> > I'm not sure why it would be an issue. Hopefully one of the maintainers of that
> > repo can weigh in. I wouldn't expect "parsing only IPMI-format EEPROMs" is a
> > design but just the current state of implementation.
>
> So long as it can function properly in its current design, i have no
> problem with FruDevice adding more parsing types. In fact, there's
> already patchsets out to add Linkedins proprietary fru type to
> FruDevice, so in terms of design, Patricks request seems reasonable.
Got it. Then I will push the code to EM.
next prev parent reply other threads:[~2022-02-11 0:41 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-08 5:10 Propose a new application for reading DIMM SPD directly Michael Shen
2022-02-08 7:11 ` Patrick Williams
2022-02-08 8:23 ` Michael Shen
2022-02-09 19:56 ` Patrick Williams
2022-02-09 20:20 ` Ed Tanous
2022-02-09 21:14 ` Patrick Williams
2022-02-09 22:45 ` Ed Tanous
2022-02-11 0:40 ` Michael Shen [this message]
2022-02-11 21:21 ` Zbigniew, Lukwinski
2022-02-14 22:17 ` Benjamin Fair
2022-02-15 1:50 ` Michael Shen
2022-02-15 20:39 ` Zbigniew, Lukwinski
2022-02-17 3:59 ` Michael Shen
2022-02-21 12:07 ` Zbigniew, Lukwinski
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAD1rtg8vM-2PckG1Cct7m5tyFJ-axvKQ_ky2z=rzV4O9mZjoWA@mail.gmail.com' \
--to=gpgpgp@google.com \
--cc=benjaminfair@google.com \
--cc=edtanous@google.com \
--cc=openbmc@lists.ozlabs.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).