From: "Arnd Bergmann" <arnd@kernel.org>
To: "David Laight" <David.Laight@ACULAB.COM>,
"Sam Ravnborg" <sam@ravnborg.org>,
"David S . Miller" <davem@davemloft.net>,
"Andreas Larsson" <andreas@gaisler.com>
Cc: "Helge Deller" <deller@gmx.de>,
"Alexander Viro" <viro@zeniv.linux.org.uk>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Alan Stern" <stern@rowland.harvard.edu>,
"Jaroslav Kysela" <perex@perex.cz>,
"Takashi Iwai" <tiwai@suse.com>,
"sparclinux@vger.kernel.org" <sparclinux@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
"linux-fbdev@vger.kernel.org" <linux-fbdev@vger.kernel.org>,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>,
"linux-sound@vger.kernel.org" <linux-sound@vger.kernel.org>
Subject: Re: [PATCH 00/27] sparc32: sunset sun4m and sun4d
Date: Wed, 20 Dec 2023 09:51:27 +0000 [thread overview]
Message-ID: <55c0b9a5-6ba3-4582-97f0-225d0119da5d@app.fastmail.com> (raw)
In-Reply-To: <9c4479a3d194450593d541ae02ad288a@AcuMS.aculab.com>
On Wed, Dec 20, 2023, at 09:34, David Laight wrote:
> From: Arnd Bergmann
>> Sent: 20 December 2023 08:37
>>
>> On Tue, Dec 19, 2023, at 22:03, Sam Ravnborg via B4 Relay wrote:
>> > TODO before this can be applied:
>> > - Ack from davem - as he is the principal sparc maintainer
>> > - Tested-by: preferably on a target or QEMU (see above)
>> > I expect bugs as there are some involved changes!
>> >
>> > Ideas for the future
>> > - Apply the most relevant downstream Gaisler patches
>> > - The ones introducing CAS should have preference as we then
>> > can drop the cmpxchg emulation
>>
>> One note about the CAS -- as far as I can tell, the absence
>> of the futex() syscall on sparc32 kernels means that no glibc
>> from the past decade can work correctly as it now requires futex
>> for its internal locking, though it does work on sparc64 kernels
>> in compat32 mode as well as the LEON3 kernel that adds futex
>> support.
>
> Does the glibc mutex 'fast path' also require a CAS instruction?
I think that depends on whether glibc is built for a CPU with
CAS or not. If it's built for 32-bit sparcv9 or leon, it should use
CAS and crash on sparcv8 without CAS. If it's built for pure
sparcv8, it should try to use an emulation that is incompatible
with the kernel futex syscall.
> Presumably having CAS also removes the 'really horrid (tm)' code
> required to make all the bitmap operations atomic?
Yes, but I'm not sure this is implemented in the leon3 tree.
With CAS enabled, at least asm/atomic.h, asm/bitops.h,
asm/cmpxchg.h and asm/spinlock.h can be implemented as efficiently
as they are in the 64-bit version.
> Seems a shame to lose old sparc32 support when (I think) the sun3
> in my cupboard would still work - if only it had a working psu.
> (The 110/220V switch wasn't connected and the FET wasn't rated
> for 450V. UK mains can be 240+10% if you are near a substation.)
sun3 support has never worked upstream. There is an old series from
20 years ago that made it work but nobody ever tried to get it
merged.
Arnd
next prev parent reply other threads:[~2023-12-20 9:51 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-19 22:03 [PATCH 00/27] sparc32: sunset sun4m and sun4d Sam Ravnborg via B4 Relay
2023-12-19 22:03 ` [PATCH 01/27] sparc32: Update defconfig to LEON SMP Sam Ravnborg via B4 Relay
2023-12-19 22:23 ` Arnd Bergmann
2023-12-20 6:43 ` Sam Ravnborg
2023-12-20 8:37 ` Arnd Bergmann
2023-12-19 22:03 ` [PATCH 02/27] sparc32: Drop sun4m/sun4d support from head_32.S Sam Ravnborg via B4 Relay
2023-12-19 22:03 ` [PATCH 03/27] sparc32: Drop floppy support Sam Ravnborg via B4 Relay
2023-12-19 22:03 ` [PATCH 04/27] sparc32: Drop sun4m specific led driver Sam Ravnborg via B4 Relay
2023-12-19 22:03 ` [PATCH 05/27] sparc32: Drop sun specific power management drivers Sam Ravnborg via B4 Relay
2023-12-19 22:03 ` [PATCH 06/27] sparc32: Drop auxio support Sam Ravnborg via B4 Relay
2023-12-19 22:03 ` [PATCH 07/27] sparc32: Drop run-time patching of ipi trap Sam Ravnborg via B4 Relay
2023-12-19 22:03 ` [PATCH 08/27] sparc32: Drop patching of interrupt vector Sam Ravnborg via B4 Relay
2023-12-19 22:03 ` [PATCH 09/27] sparc32: Drop sun4m/sun4d specific irq handling Sam Ravnborg via B4 Relay
2023-12-19 22:03 ` [PATCH 10/27] sparc32: Drop sun4d/sun4m smp support Sam Ravnborg via B4 Relay
2023-12-19 22:03 ` [PATCH 11/27] sparc32: Drop pcic support Sam Ravnborg via B4 Relay
2023-12-19 22:03 ` [PATCH 12/27] sparc32: Drop mbus support Sam Ravnborg via B4 Relay
2023-12-19 22:03 ` [PATCH 13/27] sparc32: Drop unused function __get_{phys,iospace} Sam Ravnborg via B4 Relay
2023-12-19 22:03 ` [PATCH 14/27] sparc32: Drop unused mmu models Sam Ravnborg via B4 Relay
2023-12-19 22:03 ` [PATCH 15/27] sparc32: Drop check for sparc_model Sam Ravnborg via B4 Relay
2023-12-19 22:03 ` [PATCH 16/27] sparc32: Drop use of sparc_config Sam Ravnborg via B4 Relay
2023-12-19 22:03 ` [PATCH 17/27] sparc32: Drop run-time patching of ASI instructions Sam Ravnborg via B4 Relay
2024-02-16 17:12 ` Andreas Larsson
2024-02-17 11:59 ` Sam Ravnborg
2023-12-19 22:03 ` [PATCH 18/27] sparc32: Drop support for 7 register windows Sam Ravnborg via B4 Relay
2023-12-19 22:03 ` [PATCH 19/27] sparc32: Drop additional sun4d bits Sam Ravnborg via B4 Relay
2023-12-19 22:03 ` [PATCH 20/27] sparc32: Drop unused prom ranges support Sam Ravnborg via B4 Relay
2023-12-19 22:03 ` [PATCH 21/27] sparc32: Drop unused iommu support Sam Ravnborg via B4 Relay
2023-12-19 22:03 ` [PATCH 22/27] sparc32: Drop sun4m irq support Sam Ravnborg via B4 Relay
2023-12-19 22:03 ` [PATCH 23/27] sparc32: Drop unused trampoline code Sam Ravnborg via B4 Relay
2023-12-19 22:03 ` [PATCH 24/27] sparc32: Drop config SPARC_LEON Sam Ravnborg via B4 Relay
2023-12-20 5:52 ` Greg Kroah-Hartman
2023-12-19 22:03 ` [PATCH 25/27] sparc32: Drop sbus support Sam Ravnborg via B4 Relay
2023-12-19 22:03 ` [PATCH 26/27] sbus: char: Drop now unused uctrl driver Sam Ravnborg via B4 Relay
2023-12-19 22:03 ` [PATCH 27/27] fbdev/p9100: Drop now unused driver p9100 Sam Ravnborg via B4 Relay
2024-01-02 8:26 ` Thomas Zimmermann
2024-01-02 16:31 ` Sam Ravnborg
2023-12-20 8:36 ` [PATCH 00/27] sparc32: sunset sun4m and sun4d Arnd Bergmann
2023-12-20 9:28 ` John Paul Adrian Glaubitz
2023-12-20 9:34 ` David Laight
2023-12-20 9:51 ` Arnd Bergmann [this message]
2023-12-20 9:54 ` John Paul Adrian Glaubitz
2023-12-20 10:47 ` Arnd Bergmann
2023-12-20 11:30 ` Mark Cave-Ayland
2023-12-20 15:22 ` Sam Ravnborg
2023-12-20 17:25 ` John Paul Adrian Glaubitz
2023-12-22 15:27 ` Andreas Larsson
2023-12-20 14:42 ` Kjetil Oftedal
2024-02-04 19:21 ` Sam Ravnborg
2024-02-05 5:12 ` John Paul Adrian Glaubitz
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