linux-kernel - Re: [PATCH] arm: omap: RX-51: ARM errata 430973 workaround

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Date:	Wed, 6 Mar 2013 20:13:15 +0100
From:	Pali Rohár <pali.rohar@...il.com>
To:	Tony Lindgren <tony@...mide.com>
Cc:	Nishanth Menon <nm@...com>,
	Ивайло Димитров 
	<freemangordon@....bg>, linux@....linux.org.uk,
	linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] arm: omap: RX-51: ARM errata 430973 workaround

On Wednesday 06 March 2013 18:51:21 Tony Lindgren wrote:
> * Pali Rohár <pali.rohar@...il.com> [130306 06:13]:
> > On Monday 04 March 2013 19:58:06 Tony Lindgren wrote:
> > > * Nishanth Menon <nm@...com> [130301 06:42]:
> > > > On Fri, Mar 1, 2013 at 1:47 AM, Ивайло Димитров
> > 
> > <freemangordon@....bg> wrote:
> > > > > They look similar, but they are not equivalent :). The
> > > > > first major difference is here (code taken from
> > > > > omap-smc.S)
> > > > > 
> > > > >> ENTRY(omap_smc2)
> > > > >> 
> > > > >>          stmfd   sp!, {r4-r12, lr}
> > > > >>          mov     r3, r2
> > > > >>          mov     r2, r1
> > > > >>          mov     r1, #0x0        @ Process ID
> > > > >>          mov     r6, #0xff
> > > > >>          mov     r12, #0x00      @ Secure Service ID
> > > > > 
> > > > > Always zero, while RX51 PPA expects a real value. I
> > > > > wonder if it is a bug, but anyway I don't see the id
> > > > > parameter (R0) used.
> > > > > 
> > > > >>          mov     r7, #0
> > > > >>          mcr     p15, 0, r7, c7, c5, 6
> > > > > 
> > > > > According to ARM TRM, this is "Invalidate entire
> > > > > branch predictor array"(IIUC). NFC why it is needed
> > > > > here, but this will not work on RX-51 until IBE bit
> > > > > in ACR is set.
> > > > > 
> > > > >>          dsb
> > > > >>          dmb
> > > > >>          smc     #0
> > > > > 
> > > > > RX-51 needs smc #1 ;)
> > > > > 
> > > > >>          ldmfd   sp!, {r4-r12, pc}
> > > > > 
> > > > > The next major difference is that RX-51 expects
> > > > > parameter count passed in R3[0] to be the count of
> > > > > the remaining parameters +1, but
> > > > > omap_secure_dispatcher (in omap-secure.c) is passing
> > > > > the exact count of the remaining parameters.
> > > > > 
> > > > > I guess all of the above problems can be
> > > > > fixed/workarounded, but I wonder does it worth. Not to
> > > > > say that I don't have BB around to test if the code
> > > > > still works if I make changes to
> > > > > omap2-secure.c/omap-smc.S :)
> > > > 
> > > > Yep, that was my point - instead of introducing new
> > > > functions, extending the existing functions to handle
> > > > new requirements is better solution, IMHO.
> > > 
> > > I think there have been patches posted for ARM generic SMC
> > > handling. Might be worth looking at those a bit and see if
> > > this can be made generic. I think only the SMC call
> > > numbering is different for various SoCs?
> > > 
> > > Regards,
> > > 
> > > Tony
> > 
> > Hi Tony, where are patches for ARM generic SMC handling?
> 
> Sorry don't have the link available, but I recall seeing some
> patch on linux-arm-kernel within past six months that added a
> generic smc function.. Or maybe I was dreaming or something.
> 
> Regards,
> 
> Tony

I am not able to find that patch...

-- 
Pali Rohár
pali.rohar@...il.com

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