From: Scott Wood <scottwood@freescale•com>
To: Michael Ellerman <michael@ellerman•id.au>
Cc: B07421@freescale•com, linuxppc-dev@lists•ozlabs.org,
Jia Hongtao <B38951@freescale•com>
Subject: Re: [PATCH] powerpc/85xx: workaround for chips with MSI hardware errata
Date: Wed, 13 Mar 2013 15:24:20 -0500 [thread overview]
Message-ID: <1363206260.8945.13@snotra> (raw)
In-Reply-To: <20130313050403.GB9317@concordia> (from michael@ellerman.id.au on Wed Mar 13 00:04:03 2013)
On 03/13/2013 12:04:03 AM, Michael Ellerman wrote:
> On Tue, Mar 12, 2013 at 03:48:02PM +0800, Jia Hongtao wrote:
> > The MPIC chip with version 2.0 has a MSI errata (errata PIC1 of =20
> mpc8544),
> > It causes that neither MSI nor MSI-X can work fine. This is a =20
> workaround
> > to allow MSI-X to function properly.
>=20
> You say "neither MSI nor MSI-X can work fine", which I take to mean
> "both MSI and MSI-X do not work".
>=20
> But then you say this is a workaround to allow MSI-X to work.
>=20
> So what I think you mean is, the erratum prevents both MSI and MSI-X
> from working. This is a workaround that allows MSI-X to work, and in =20
> addition
> the patch prevents MSI from being used on chips with the erratum -
> because there is no workaround for MSI.
There actually is a workaround for MSI, but it's more complicated and =20
not implemented by this patch.
We could also possibly get away with allowing exactly one MSI =20
(byteswapping doesn't matter if the value is zero) -- not sure how hard =20
that would be.
> > + list_for_each_entry(msi, &msi_head, list)
> > + if (msi->feature & MSI_HW_ERRATA_ENDIAN)
> > + return -EINVAL;
>=20
> I take it you're happy preventing MSI for all devices even if only a
> single chip in the machine has the erratum? In practice you probably
> have all or none with the erratum right?
Yes, it's all integrated onto one chip (the SoC itself). In fact there =20
should only be one MSI block on these chips.
-Scott=
next prev parent reply other threads:[~2013-03-13 20:24 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-12 7:48 [PATCH] powerpc/85xx: workaround for chips with MSI hardware errata Jia Hongtao
2013-03-13 5:04 ` Michael Ellerman
2013-03-13 7:14 ` Jia Hongtao-B38951
2013-03-13 20:24 ` Scott Wood [this message]
2013-03-14 11:04 ` Jia Hongtao-B38951
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=1363206260.8945.13@snotra \
--to=scottwood@freescale$(echo .)com \
--cc=B07421@freescale$(echo .)com \
--cc=B38951@freescale$(echo .)com \
--cc=linuxppc-dev@lists$(echo .)ozlabs.org \
--cc=michael@ellerman$(echo .)id.au \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
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