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From: Sven Schnelle <svens@stackframe.org>
To: Helge Deller <deller@gmx.de>
Cc: John David Anglin <dave.anglin@bell.net>,
	Rolf Eike Beer <eike-kernel@sf-tec.de>,
	Carlo Pisani <carlojpisani@gmail.com>,
	linux-parisc@vger.kernel.org,
	James Bottomley <James.Bottomley@hansenpartnership.com>
Subject: Re: [PATCH v3] parisc: Fix crash due alternative coding for NP iopdir_fdc bit
Date: Thu, 30 May 2019 21:55:43 +0200	[thread overview]
Message-ID: <20190530195543.GB683@t470p.stackframe.org> (raw)
In-Reply-To: <61253aef-2571-f8bb-756a-bf2018e533e4@gmx.de>

Hi,

On Wed, May 29, 2019 at 04:15:03PM +0200, Helge Deller wrote:
> >> Exactly. And as:
> >>
> >> a) All C3600 PDC versions clear the NP bit
> >> b) All C37XX/J5000 PDC version set the NP bit
> >>
> >> i don't think there's some bug in the PDC. I would guess that the patch Carlo
> >> reported to fix issues is just hiding the real problem. Would be interesting
> >> to run Carlo's Test on a C37XX.
> >
> > Probably, hardware cache coherent I/O is not implemented correctly for Elroy based systems.
> > https://www.hpl.hp.com/hpjournal/96feb/feb96a6.pdf
> > Does it work on C360?
> 
> I slowly start to get confused...
> Just thinking about another possibility: Maybe we can rely on the value of the
> NP iopdir_fdc bit only on machines with >= PA8700 CPUs?
> For older machines (which would need opdir_fdc) HP-UX or other operating
> systems decides on the found CPU.
> This would explain why it's not  set on Carlo's C3600, and if Sven's C240
> (with a PA8200 CPU) doesn't has the bit set too, then this could explain this theory.

I just re-tested my kexec branch, and the HPMC i was seeing when kexec'ing a new
kernel on my J5000 is now gone with Helge's patch. J5000 also has PCX-W. It was
only triggered when i had SMP enabled, but this is somehow not suprising given
the fact that a cache flush was missing.

Regards
Sven

  parent reply	other threads:[~2019-05-30 19:55 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-27 19:20 [PATCH v3] parisc: Fix crash due alternative coding for NP iopdir_fdc bit Helge Deller
2019-05-27 19:35 ` Carlo Pisani
2019-05-27 20:13   ` John David Anglin
2019-05-27 20:22     ` Sven Schnelle
2019-05-27 20:49       ` John David Anglin
2019-05-27 20:15   ` Sven Schnelle
2019-05-28 11:06     ` Sven Schnelle
2019-05-28 11:28       ` Rolf Eike Beer
2019-05-28 15:41         ` Sven Schnelle
2019-05-28 15:52           ` Helge Deller
     [not found]       ` <e81b7ae4-3126-5fda-58e4-4a83bd4fcfcf@bell.net>
2019-05-28 15:11         ` Helge Deller
2019-05-28 15:38           ` Sven Schnelle
2019-05-28 17:06             ` John David Anglin
2019-05-28 17:24               ` Rolf Eike Beer
2019-05-28 17:39                 ` Sven Schnelle
2019-05-28 18:40                   ` John David Anglin
2019-05-29 14:15                     ` Helge Deller
2019-05-29 17:01                       ` John David Anglin
2019-05-30 19:55                       ` Sven Schnelle [this message]
2019-05-30 20:59                         ` Sven Schnelle
2019-05-31 12:23                           ` John David Anglin
2019-06-02 10:29                             ` Carlo Pisani
2019-06-02 14:45                               ` John David Anglin
2019-06-02 14:38                             ` John David Anglin
2019-06-02 16:12                               ` John David Anglin
2019-05-27 19:41 ` John David Anglin
2019-05-27 20:11   ` Helge Deller
2019-05-27 20:16     ` Carlo Pisani
2019-05-27 20:45     ` John David Anglin

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