linux-kernel - Re: [PATCH] powerpc/8xx: use SPRN_EIE and SPRN

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Message-ID: <20160818175411.GD24467@gate.crashing.org>
Date:   Thu, 18 Aug 2016 12:54:11 -0500
From:   Segher Boessenkool <segher@...nel.crashing.org>
To:     Christophe Leroy <christophe.leroy@....fr>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Scott Wood <oss@...error.net>, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc/8xx: use SPRN_EIE and SPRN_EID to enable/disable interrupts

On Thu, Aug 18, 2016 at 06:52:47PM +0200, Christophe Leroy wrote:
> Le 18/08/2016 à 18:34, Segher Boessenkool a écrit :
> >On Thu, Aug 18, 2016 at 05:56:02PM +0200, Christophe Leroy wrote:
> >>The 8xx has two special registers called EID (External Interrupt
> >>Disable) and EIE (External Interrupt Enable) for clearing/setting
> >>EE in MSR. It avoids the three instructions set mfmsr/ori/mtmsr or
> >>mfmsr/rlwinm/mtmsr.
> >
> >All 8xx?  What other models?  (5xx for example).
> 
> At least 823, 860, 866 and 885 have it.

I haven't been able to find a manual for all 8xx.  But there is AN2055,
which suggests EIE etc. is for all 8xx indeed.

> Looks like the 5xx have it too (at least the 565). Does Linux supports 
> that one at all ?

All 5xx have it, there is a manual for *that* ("RCPU") :-)

> >>+/* Special MSR manipulation registers */
> >>+#define SPRN_EIE	80	/* External interrupt enable (EE=1, RI=1) */
> >>+#define SPRN_EID	81	/* External interrupt disable (EE=0, RI=1) */
> >>+#define SPRN_NRI	81	/* Non Recoverable interrupt (EE=0, RI=0) */

Is it correct to set RI in all places you do now?

> >This is wrong (NRI is 82).  Don't write code you cannot test / don't submit
> >code you haven't tested?  :-)
> 
> Oops. You're right, copy/paste failure.
> Was tested on an 885. Unfortunatly SPRN_NRI is not used (yet) :-(

Well, that was my point!


Segher