From: David Miller <davem@davemloft.net>
To: andreas@gaisler.com
Cc: triegel@redhat.com, libc-alpha@sourceware.org,
adhemerval.zanella@linaro.org, carlos@redhat.com,
software@gaisler.com
Subject: Re: [RFC][PATCH 0/2] Make sparcv8 work again on cas enabled hardware
Date: Fri, 04 Nov 2016 15:23:00 -0000 [thread overview]
Message-ID: <20161104.112254.1930090925346599920.davem@davemloft.net> (raw)
In-Reply-To: <581C62A2.8050204@gaisler.com>
From: Andreas Larsson <andreas@gaisler.com>
Date: Fri, 04 Nov 2016 11:27:46 +0100
> On 2016-11-03 18:22, David Miller wrote:
>> From: Torvald Riegel <triegel@redhat.com>
>> Date: Thu, 03 Nov 2016 16:39:21 +0100
>>
>>> Is there any difference between the additional CAS on a v8 and the CAS
>>> on a v9? If there should be none (eg, same instruciton encoding
>>> etc.),
>>> we wouldn't need a runtime check for this, would we?
>>
>> A quick look at binutils shows that the encoding appears to be the
>> same.
>
> The general encoding of the CASA instruction is the same, but on
> sparcv9 the ASI to use is the primary address space ASI 0x80 and on
> LEON the ASI to use is the user data space ASI 0xa. So different
> instruction encodings needs to be used.
>
> Unfortunately there is no way general way short of trying to use the
> CASA instruction and taking a care of a possible illegal instruction
> to detect if a LEON3 system has CAS or not. But CAS support is implied
> by the the -mcpu=leon3 flag, and LEON3 systems without CAS can use
> -mcpu=v8.
This really should be advertised in the _dl_hwcaps. We should try as
hard as possible to allow dynamic discovery of this.
next prev parent reply other threads:[~2016-11-04 15:23 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-01 15:08 Andreas Larsson
2016-11-01 15:08 ` [RFC][PATCH 2/2] sparc32: Use cas for atomic_* operations and use general pthread_barrier_wait Andreas Larsson
2016-11-04 18:37 ` David Miller
2016-11-04 18:44 ` David Miller
2016-11-01 15:08 ` [RFC][PATCH 1/2] sparc32: Mark sendmsg and recvmsg system calls as unsupported Andreas Larsson
2016-11-01 17:28 ` Adhemerval Zanella
2016-11-02 11:38 ` Andreas Larsson
2016-11-02 12:49 ` Adhemerval Zanella
2016-11-04 18:36 ` David Miller
2016-11-01 16:00 ` [RFC][PATCH 0/2] Make sparcv8 work again on cas enabled hardware Torvald Riegel
2016-11-01 16:09 ` David Miller
2016-11-01 16:46 ` Torvald Riegel
2016-11-01 16:51 ` David Miller
2016-11-02 10:05 ` Torvald Riegel
2016-11-02 11:29 ` Andreas Larsson
2016-11-02 15:32 ` David Miller
2016-11-02 22:33 ` Torvald Riegel
2016-11-03 2:52 ` David Miller
2016-11-03 15:39 ` Torvald Riegel
2016-11-03 17:22 ` David Miller
2016-11-03 18:41 ` Adhemerval Zanella
2016-11-03 20:33 ` David Miller
2016-11-03 21:29 ` Adhemerval Zanella
2016-11-03 22:25 ` Torvald Riegel
2016-11-04 10:28 ` Andreas Larsson
2016-11-04 15:23 ` David Miller [this message]
2016-11-04 13:55 ` Richard Henderson
2016-11-04 15:31 ` David Miller
2016-11-04 16:10 ` Richard Henderson
2016-11-04 14:04 ` Richard Henderson
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