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From: tony@atomide.com (Tony Lindgren)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] omap4: Fix ULPI PHY init for ES1.0 SDP (Re: 4430SDP boot failure)
Date: Fri, 14 Jan 2011 16:37:34 -0800	[thread overview]
Message-ID: <20110115003734.GV4957@atomide.com> (raw)
In-Reply-To: <20110115002531.GF22505@n2100.arm.linux.org.uk>

* Russell King - ARM Linux <linux@arm.linux.org.uk> [110114 16:24]:
> On Fri, Jan 14, 2011 at 04:12:55PM -0800, Tony Lindgren wrote:
> > * Russell King - ARM Linux <linux@arm.linux.org.uk> [110114 15:58]:
> > > 
> > > # ARMv6k
> > > config CPU_32v6K
> > >         bool "Support ARM V6K processor extensions" if !SMP
> > >         depends on CPU_V6 || CPU_V7
> > >         default y if SMP && !(ARCH_MX3 || ARCH_OMAP2)
> > > 
> > > OMAP2 prevents the selection of armv6k support.  This is probably a very
> > > bad idea if you want to run the resulting kernel on SMP hardware as it
> > > removes a barrier in the spinlock code and disables the SMP-safe bitops.
> > 
> > I have some ideas to fix this. Unfortunately it will be inefficient
> > as spinlock.h can be included from modules too :( I was thinking we can
> > implement dsb_sev in the proc-*.S functions for the unoptimized multi-arm
> > builds.
> 
> For spinlocks, the important thing is the barrier.  The wfe/sev are an
> optimization.  The barrier contained with the ifdef is a valid V6
> instruction.

OK, great it's just drain WB. Then we can do the ussual iffdeffery
on it for multi-arm builds as it does not depend on the 6K extensions.
I can do a patch for this on Monday, gotta run now.
 
> > > The original patch which started turning this off was from the MX3 stuff,
> > > but without explaination.
> > > 
> > > However, OMAP extended this to disabling the select statement for CPU_32v6K
> > > even if CPU_V7 is set:
> > > 
> > >  config CPU_V7
> > >         bool "Support ARM V7 processor" if ARCH_INTEGRATOR || MACH_REALVIEW_EB |-       select CPU_32v6K
> > > +       select CPU_32v6K if !ARCH_OMAP2
> > > 
> > > Arguably, SMP _requires_ CPU_32v6K to be enabled for a safe kernel, and this
> > > patch should not have been merged.
> > 
> > The only way we can fix that is do smp_on_up style rewriting of the assembly
> > during init between CPUv6 and v6K. Want me to do a patch for that?
> 
> The bitops code is quite different between the two versions, and I doubt
> the smp_on_up rewriting will look at all pretty.  I think it needs an
> alternative idea - like not using the 'byte' operations at all.
> 
> Whether we have any code which passes non-word aligned pointers to bitops
> isn't particularly known - in theory they should all be unsigned long *'s,
> so should be word-aligned.  Who knows what filesystems do though... and
> such a change could be disasterous to peoples data if the block/inode
> bitmaps get corrupted.

Hmm, how about emulation of those instructions for non-v6K ARMv6 processors?
I guess we could do some address checking in the bitops functions too for
multi-arm builds..
 
> IOW, such a change needs testing on a box where a range of filesystems are
> used, and the filesystems can be thrown away if corrupted.

Or we could patch in the address checking first and only disable it
later if now warnings.

Tony

  reply	other threads:[~2011-01-15  0:37 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20110106170805.GE1198@n2100.arm.linux.org.uk>
     [not found] ` <20110106180030.GA8249@n2100.arm.linux.org.uk>
     [not found]   ` <20110106182023.GV7771@atomide.com>
     [not found]     ` <20110106203238.GH1198@n2100.arm.linux.org.uk>
     [not found]       ` <20110106204053.GA7771@atomide.com>
     [not found]         ` <20110107161230.GR1198@n2100.arm.linux.org.uk>
     [not found]           ` <20110110185209.GC4957@atomide.com>
2011-01-11 23:16             ` [PATCH] omap4: Fix ULPI PHY init for ES1.0 SDP (Re: 4430SDP boot failure) Tony Lindgren
2011-01-13  8:52               ` Anand Gadiyar
2011-01-13  9:15                 ` Russell King - ARM Linux
2011-01-13 15:51                   ` Tony Lindgren
2011-01-13 16:49                     ` Russell King - ARM Linux
2011-01-14 17:29                       ` Tony Lindgren
2011-01-14 19:18                       ` Paul Walmsley
2011-01-14 21:20                         ` Russell King - ARM Linux
2011-01-14 22:07                           ` Paul Walmsley
2011-01-14 23:10                           ` Paul Walmsley
2011-01-14 23:58                             ` Russell King - ARM Linux
2011-01-15  0:12                               ` Tony Lindgren
2011-01-15  0:25                                 ` Russell King - ARM Linux
2011-01-15  0:37                                   ` Tony Lindgren [this message]
2011-01-15 17:04                                     ` Russell King - ARM Linux
2011-01-17  8:35                                       ` Sascha Hauer
2011-02-01 12:55               ` Anand Gadiyar
2011-02-02  1:10                 ` Tony Lindgren
2011-02-02  6:05                   ` Santosh Shilimkar
2011-02-02 19:48                     ` Tony Lindgren
2011-02-03  8:43                       ` Santosh Shilimkar
2011-02-12  8:46                         ` Santosh Shilimkar
2011-02-24 17:38                           ` Tony Lindgren
2011-02-25  5:33                             ` Santosh Shilimkar
2011-02-25 17:49                               ` Tony Lindgren
2011-02-02 18:43                   ` Anand Gadiyar
2011-02-02 19:50                     ` Tony Lindgren

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