From: Russell Currey <ruscur@russell•cc>
To: Michael Ellerman <mpe@ellerman•id.au>, linuxppc-dev@lists•ozlabs.org
Cc: gwshan@linux•vnet.ibm.com
Subject: Re: [PATCH] powernv/pci: Add PHB register dump debugfs handle
Date: Tue, 26 Jul 2016 15:37:23 +1000 [thread overview]
Message-ID: <1469511443.5228.2.camel@russell.cc> (raw)
In-Reply-To: <146949753931.3859.11305398485148230358@concordia>
On Tue, 2016-07-26 at 11:45 +1000, Michael Ellerman wrote:
> Quoting Russell Currey (2016-07-22 15:23:36)
> >
> > On EEH events the kernel will print a dump of relevant registers.
> > If EEH is unavailable (i.e. CONFIG_EEH is disabled, a new platform
> > doesn't have EEH support, etc) this information isn't readily available.
> >
> > Add a new debugfs handler to trigger a PHB register dump, so that this
> > information can be made available on demand.
>
> This is a bit weird.
>
> It's a debugfs file, but when you read from it you get nothing (I think,
> you have no read() defined).
>
> When you write to it, regardless of what you write, the kernel spits
> some stuff out to dmesg and throws away whatever you wrote.
>
> Ideally pnv_pci_dump_phb_diag_data() would write its output to a buffer,
> which we could then either send to dmesg, or give to debugfs. But that
> might be more work than we want to do for this.
>
> If we just want a trigger file, then I think it'd be preferable to just
> use a simple attribute, with a set and no show, eg. something like:
>
> static int foo_set(void *data, u64 val)
> {
> if (val != 1)
> return -EINVAL;
>
> ...
>
> return 0;
> }
>
> DEFINE_SIMPLE_ATTRIBUTE(fops_foo, NULL, foo_set, "%llu\n");
>
> That requires that you write "1" to the file to trigger the reg dump.
I don't think I can use this here. Triggering the diag dump on the given PHB
(these are in /sys/kernel/debug/powerpc/PCI####), and that PHB is retrieved from
the file handler. It looks like I have no access to the file struct if using a
simple getter/setter.
>
>
> >
> > diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c
> > b/arch/powerpc/platforms/powernv/pci-ioda.c
> > index 891fc4a..ada2f3c 100644
> > --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> > +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> > @@ -3036,6 +3068,9 @@ static void pnv_pci_ioda_create_dbgfs(void)
> > if (!phb->dbgfs)
> > pr_warning("%s: Error on creating debugfs on
> > PHB#%x\n",
> > __func__, hose->global_number);
> > +
> > + debugfs_create_file("regdump", 0200, phb->dbgfs, hose,
> > + &pnv_pci_debug_ops);
> > }
>
> You shouldn't be trying to create the file if the directory create failed. So
> the check for (!phb->dbgfs) should probably print and then continue.
Good catch.
>
> And a better name would be "dump-regs", because it indicates that the file
> does
> something, rather than is something.
That is indeed better.
>
> cheers
next prev parent reply other threads:[~2016-07-26 5:37 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-22 5:23 [PATCH] powernv/pci: Add PHB register dump debugfs handle Russell Currey
2016-07-22 6:36 ` Gavin Shan
2016-07-25 17:53 ` Tyrel Datwyler
2016-07-25 23:45 ` Gavin Shan
2016-07-26 1:06 ` Michael Ellerman
2016-07-26 0:37 ` Russell Currey
2016-07-26 1:45 ` Michael Ellerman
2016-07-26 5:37 ` Russell Currey [this message]
2016-07-26 9:47 ` Michael Ellerman
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=1469511443.5228.2.camel@russell.cc \
--to=ruscur@russell$(echo .)cc \
--cc=gwshan@linux$(echo .)vnet.ibm.com \
--cc=linuxppc-dev@lists$(echo .)ozlabs.org \
--cc=mpe@ellerman$(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