linux-kernel - RE: [PATCH] ARM: ep93xx: don't use clang IAS for crunch

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Message-ID: <BYAPR01MB5621DC2003DA49EA64AD46A0D09D9@BYAPR01MB5621.prod.exchangelabs.com>
Date:   Fri, 26 Feb 2021 19:32:42 +0000
From:   Hartley Sweeten <HartleyS@...ionengravers.com>
To:     Alexander Sverdlin <alexander.sverdlin@...il.com>,
        Arnd Bergmann <arnd@...nel.org>
CC:     "soc@...nel.org" <soc@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Russell King <linux@...linux.org.uk>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "clang-built-linux@...glegroups.com" 
        <clang-built-linux@...glegroups.com>
Subject: RE: [PATCH] ARM: ep93xx: don't use clang IAS for crunch

On Friday, February 26, 2021 12:23 PM, Alexander Sverdlin wrote:
> On Fri, 2021-02-26 at 17:43 +0100, Arnd Bergmann wrote:
>> Randconfig builds with ep93xx fail with the clang integrated assembler 
>> that does not understand the maverick crunch extensions:
>> 
>> arch/arm/mach-ep93xx/crunch-bits.S:94:2: error: invalid instruction
>>  cfstr64 mvdx0, [r1, #0] @ save 64b registers
>> 
>> It is unclear if anyone is still using support for crunch: gcc-4.8 
>> dropped it in 2012 when it was already too broken to be used 
>> reliabled. glibc support existed as an external patch but was never merged upstream.
>> We could consider removing the last bits of the kernel support as well.
>
> This was my impression already in 2006, that Cirrus is not going to work on Crunch support. From my PoV it's OK to remove the support in the kernel completely.

Martin Guy did a lot of work trying to get the maverick crunch working but I was never able to successfully use it for anything. It "kind" of works but depending on the EP93xx silicon revision there are still a number of hardware bugs that either give imprecise or garbage results.

I have no problem with removing the kernel support for the maverick crunch.

Hartley