Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933299Ab1ESNxy (ORCPT ); Thu, 19 May 2011 09:53:54 -0400 Received: from mail-bw0-f46.google.com ([209.85.214.46]:38961 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933140Ab1ESNxx convert rfc822-to-8bit (ORCPT ); Thu, 19 May 2011 09:53:53 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=pvJs5jSmxm8GdCrpSnhx25VaDn7LdOdE2cMVZAcPkWKLSj4Ih82QsB3Mu2rM7HEnWk Zz3unRmn5L2y2Z4Ga+gb+rqmq3cUuzvvTOyCBwcmT32q/HDqcK3u3sX8tdQW6m6BTzMq XSqCftz1IHw3lKXix4+LKoNNYLSNJakC9tNlw= MIME-Version: 1.0 In-Reply-To: <425.1305784718@neuling.org> References: <1305753895-24845-1-git-send-email-ericvh@gmail.com> <1305753895-24845-3-git-send-email-ericvh@gmail.com> <425.1305784718@neuling.org> Date: Thu, 19 May 2011 08:53:51 -0500 Message-ID: Subject: Re: [PATCH 3/7] [RFC] add support for BlueGene/P FPU From: Eric Van Hensbergen To: Michael Neuling Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, bg-linux@lists.anl-external.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3662 Lines: 98 On Thu, May 19, 2011 at 12:58 AM, Michael Neuling wrote: > Eric, > >> This patch adds save/restore register support for the BlueGene/P >> double hummer FPU. > > What does this mean? ?Needs more details here. > Hi Mikey, any specific details you are looking for here? AFAIK these patches are required for the kernel to save/restore the double hummer properly. >> >> +#ifdef CONFIG_BGP >> +#define LFPDX(frt, ra, rb) ? .long (31<<26)|((frt)<<21)|((ra)<<16)| \ >> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ((rb)<<11)|(462<<1) >> +#define STFPDX(frt, ra, rb) ?.long (31<<26)|((frt)<<21)|((ra)<<16)| \ >> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ((rb)<<11)|(974<<1) >> +#endif /* CONFIG_BGP */ > > Put these in arch/powerpc/include/asm/ppc-opcode.h and reformat to fit > whats there already. > > Also, don't need to put these defines inside a #ifdef. > Sure, I'll fix that up. >> +#ifdef CONFIG_BGP >> +#define SAVE_FPR(n, b, base) li b, THREAD_FPR0+(16*(n)); STFPDX(n, base, b) >> +#define REST_FPR(n, b, base) li b, THREAD_FPR0+(16*(n)); LFPDX(n, base, b) > > 16*? ?Are these FP regs 64 or 128 bits wide? ?If 128 you are doing to > have to play with TS_WIDTH to get the size of the FPs correct in the > thread_struct. > > I think there's a bug here. > I actually have three different versions of this code from different source patches that I'm drawing from - so your help in figuring out the best way to approach this is appreciated. The kittyhawk version of the code has 8* instead of 16*. According to the docs: "Each of the two FPU units contains 32 64-bit floating point registers for a total of 64 FP registers per processor." which would seem to point to the kittyhawk version - but they have a second SAVE_32SFPRS for the second hummer. What wasn't clear to me with this version of the code was whether or not they were doing something clever like saving the pair of the 64-bit FPU registers in a single 128-bit slot (seems plausible). If this is not the way to go, I can certainly switch the kittyhawk version of the patch with the *, the extra SAVE32SFPR and the extra double hummer specific storage space in the thread_struct. If it would help I can post an alternate version of the patch for discussion with the kittyhawk version. >> ?/* >> diff --git a/arch/powerpc/platforms/44x/Kconfig b/arch/powerpc/platforms/44x/ > Kconfig >> index f485fc5f..24a515e 100644 >> --- a/arch/powerpc/platforms/44x/Kconfig >> +++ b/arch/powerpc/platforms/44x/Kconfig >> @@ -169,6 +169,15 @@ config YOSEMITE >> ? ? ? help >> ? ? ? ? This option enables support for the AMCC PPC440EP evaluation board. >> >> +config ? ? ? BGP > > Does this FPU feature have a specific name like double hammer? ?I'd > rather have the BGP defconfig depend on PPC_FPU_DOUBLE_HUMMER, or > something like that... > >> + ? ? bool "Blue Gene/P" >> + ? ? depends on 44x >> + ? ? default n >> + ? ? select PPC_FPU >> + ? ? select PPC_DOUBLE_FPU > > ... in fact, it seem you are doing something like these here but you > don't use PPC_DOUBLE_FPU anywhere? > A fair point. I'm fine with calling it DOUBLE_HUMMER, but I wasn't sure if that was "too internal" of a name for the kernel. Let me know and I'll fix it up. I'll also change the CONFIG_BGP defines in the FPU code to PPC_DOUBLE_FPU or PPC_DOUBLE_HUMMER depending on what the community decides. Thanks for the feedback! -eric -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/