From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: "tiejun.chen" <tiejun.chen@windriver.com>
Cc: Xie Shaohui-B21989 <B21989@freescale.com>,
Liu Qiang-B32616 <B32616@freescale.com>,
Zang Roy-R61911 <r61911@freescale.com>,
Timur Tabi <timur@tabi.org>,
Fleming Andy-AFLEMING <afleming@freescale.com>,
Bhushan Bharat-R65777 <R65777@freescale.com>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
Subject: Re: fsqrt
Date: Fri, 07 Jun 2013 22:07:02 +1000 [thread overview]
Message-ID: <1370606822.3766.379.camel@pasglop> (raw)
In-Reply-To: <51B1A18A.6030002@windriver.com>
On Fri, 2013-06-07 at 17:02 +0800, tiejun.chen wrote:
> On 06/07/2013 04:53 PM, Benjamin Herrenschmidt wrote:
> > On Fri, 2013-06-07 at 15:46 +0800, tiejun.chen wrote:
> >> On 06/07/2013 03:41 PM, Benjamin Herrenschmidt wrote:
> >>> Another question...
> >>>
> >>> Do you guys happen to have a patch to emulate fsqrt in the kernel ?
> >>
> >> Seems this is already emulated:
> >>
> >> arch/powerpc/math-emu/fsqrt.c
> >>
> >> You can enable CONFIG_MATH_EMULATION to try.
> >
> > Is math emu expected to work at all on top of a real FPU ? I though it
> > didn't ... maybe I'm wrong.
>
> As I understand often the real FPU can't support all float instructions, so we
> have to enable this to emulate those unsupported float instructions in that
> scenario.
Ok, two things come to mind here:
- do_mathemu doesn't do giveup_fpu() so the FPU state might still be
in the "live" FP registers and not in the thread_struct, so it can't
work... unless I missed something.
- mathemu uses solely integers. For something like fsqrt it's going to
suck a lot more than implementing using floating points in the kernel.
Cheers,
Ben.
next prev parent reply other threads:[~2013-06-07 12:07 UTC|newest]
Thread overview: 78+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-16 4:47 SATA FSL and upstreaming Benjamin Herrenschmidt
2013-05-16 5:45 ` Benjamin Herrenschmidt
2013-05-16 5:55 ` tiejun.chen
2013-05-16 6:06 ` Benjamin Herrenschmidt
2013-05-16 5:59 ` Zang Roy-R61911
2013-05-16 6:01 ` Bhushan Bharat-R65777
2013-05-16 6:05 ` Zang Roy-R61911
2013-05-16 6:09 ` Benjamin Herrenschmidt
2013-05-16 6:17 ` tiejun.chen
2013-05-16 6:20 ` Zang Roy-R61911
2013-05-16 6:25 ` tiejun.chen
2013-05-16 7:20 ` Zang Roy-R61911
2013-05-16 6:26 ` Benjamin Herrenschmidt
2013-05-16 6:21 ` Benjamin Herrenschmidt
2013-05-16 6:35 ` tiejun.chen
2013-05-16 6:37 ` Zang Roy-R61911
2013-05-16 6:40 ` Benjamin Herrenschmidt
2013-05-16 6:43 ` tiejun.chen
2013-05-16 6:48 ` Bhushan Bharat-R65777
2013-05-16 6:49 ` Zang Roy-R61911
2013-05-16 6:53 ` Benjamin Herrenschmidt
2013-05-16 6:56 ` tiejun.chen
2013-05-16 7:01 ` Zang Roy-R61911
2013-05-16 7:05 ` Benjamin Herrenschmidt
2013-05-16 7:13 ` Bhushan Bharat-R65777
2013-05-16 7:26 ` Benjamin Herrenschmidt
2013-05-16 7:20 ` Xie Shaohui-B21989
2013-05-16 7:25 ` Bhushan Bharat-R65777
2013-05-16 6:59 ` Benjamin Herrenschmidt
2013-05-16 7:17 ` Zang Roy-R61911
2013-05-16 6:52 ` Benjamin Herrenschmidt
2013-05-16 14:56 ` Timur Tabi
2013-06-07 3:52 ` Benjamin Herrenschmidt
2013-06-07 4:39 ` Benjamin Herrenschmidt
2013-06-07 4:45 ` Zang Roy-R61911
2013-06-07 4:47 ` Benjamin Herrenschmidt
2013-06-07 4:50 ` Zang Roy-R61911
2013-06-07 7:41 ` fsqrt Benjamin Herrenschmidt
2013-06-07 7:45 ` fsqrt Zang Roy-R61911
2013-06-07 8:53 ` fsqrt Benjamin Herrenschmidt
2013-06-07 8:59 ` fsqrt Benjamin Herrenschmidt
2013-06-07 10:48 ` fsqrt David Laight
2013-06-07 12:14 ` fsqrt Benjamin Herrenschmidt
2013-06-07 19:19 ` fsqrt Kumar Gala
2013-06-07 23:23 ` fsqrt Benjamin Herrenschmidt
2013-06-07 23:25 ` fsqrt Benjamin Herrenschmidt
2013-06-07 23:30 ` fsqrt Benjamin Herrenschmidt
2013-06-08 0:20 ` fsqrt Dan Malek
2013-06-08 0:34 ` fsqrt Benjamin Herrenschmidt
2013-06-08 1:13 ` fsqrt Dan Malek
2013-06-08 4:31 ` fsqrt Benjamin Herrenschmidt
2013-06-09 6:32 ` fsqrt Benjamin Herrenschmidt
2013-06-07 7:46 ` fsqrt tiejun.chen
2013-06-07 8:53 ` fsqrt Benjamin Herrenschmidt
2013-06-07 9:02 ` fsqrt tiejun.chen
2013-06-07 12:07 ` Benjamin Herrenschmidt [this message]
2013-06-07 7:05 ` FSL 64-bit DMA window question Benjamin Herrenschmidt
2013-06-07 7:58 ` Zang Roy-R61911
2013-06-07 8:55 ` Benjamin Herrenschmidt
2013-06-07 9:44 ` Zang Roy-R61911
2013-06-07 12:09 ` Benjamin Herrenschmidt
[not found] ` <1370642488.6813.15@snotra>
2013-06-07 22:02 ` Scott Wood
2013-06-07 22:09 ` Benjamin Herrenschmidt
2013-06-07 22:34 ` Scott Wood
2013-06-07 22:39 ` Benjamin Herrenschmidt
2013-06-07 23:29 ` Scott Wood
2013-06-07 23:33 ` Benjamin Herrenschmidt
2013-06-07 12:09 ` SATA FSL and upstreaming Timur Tabi
2013-05-16 6:17 ` Zang Roy-R61911
2013-05-16 6:23 ` Benjamin Herrenschmidt
2013-05-16 6:33 ` Bhushan Bharat-R65777
2013-05-16 6:34 ` Benjamin Herrenschmidt
2013-05-16 6:35 ` Zang Roy-R61911
2013-05-16 6:37 ` Benjamin Herrenschmidt
2013-05-16 6:41 ` tiejun.chen
2013-05-16 6:48 ` Zang Roy-R61911
2013-05-16 6:24 ` Xie Shaohui-B21989
2013-05-16 6:31 ` Benjamin Herrenschmidt
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