From: "Arnd Bergmann" <arnd@arndb.de>
To: "Neil Armstrong" <neil.armstrong@linaro.org>,
"Arnd Bergmann" <arnd@kernel.org>,
linux-kernel@vger.kernel.org
Cc: "Vineet Gupta" <vgupta@kernel.org>,
"Russell King" <linux@armlinux.org.uk>,
"Linus Walleij" <linus.walleij@linaro.org>,
"Catalin Marinas" <catalin.marinas@arm.com>,
"Will Deacon" <will@kernel.org>, guoren <guoren@kernel.org>,
"Brian Cain" <bcain@quicinc.com>,
"Geert Uytterhoeven" <geert@linux-m68k.org>,
"Michal Simek" <monstr@monstr.eu>,
"Thomas Bogendoerfer" <tsbogend@alpha.franken.de>,
"Dinh Nguyen" <dinguyen@kernel.org>,
"Stafford Horne" <shorne@gmail.com>,
"Helge Deller" <deller@gmx.de>,
"Michael Ellerman" <mpe@ellerman.id.au>,
"Christophe Leroy" <christophe.leroy@csgroup.eu>,
"Paul Walmsley" <paul.walmsley@sifive.com>,
"Palmer Dabbelt" <palmer@dabbelt.com>,
"Rich Felker" <dalias@libc.org>,
"John Paul Adrian Glaubitz" <glaubitz@physik.fu-berlin.de>,
"David S . Miller" <davem@davemloft.net>,
"Max Filippov" <jcmvbkbc@gmail.com>,
"Christoph Hellwig" <hch@lst.de>,
"Robin Murphy" <robin.murphy@arm.com>,
"Lad, Prabhakar" <prabhakar.mahadev-lad.rj@bp.renesas.com>,
"Conor.Dooley" <conor.dooley@microchip.com>,
linux-snps-arc@lists.infradead.org,
linux-arm-kernel@lists.infradead.org,
"linux-oxnas@groups.io" <linux-oxnas@groups.io>,
"linux-csky@vger.kernel.org" <linux-csky@vger.kernel.org>,
linux-hexagon@vger.kernel.org, linux-m68k@lists.linux-m68k.org,
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"linux-openrisc@vger.kernel.org" <linux-openrisc@vger.kernel.org>,
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sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org,
"Daniel Golle" <daniel@makrotopia.org>
Subject: Re: [PATCH 18/21] ARM: drop SMP support for ARM11MPCore
Date: Thu, 30 Mar 2023 12:03:16 +0200 [thread overview]
Message-ID: <6a5bd3a3-87e0-4a24-89ca-d265b0817a95@app.fastmail.com> (raw)
In-Reply-To: <d7f36a28-0cae-a035-791b-363754aefeee@linaro.org>
On Thu, Mar 30, 2023, at 09:48, Neil Armstrong wrote:
> On 27/03/2023 14:13, Arnd Bergmann wrote:
>> From: Arnd Bergmann <arnd@arndb.de>
>>
>> The cache management operations for noncoherent DMA on ARMv6 work
>> in two different ways:
>>
>> * When CONFIG_DMA_CACHE_RWFO is set, speculative prefetches on in-flight
>> DMA buffers lead to data corruption when the prefetched data is written
>> back on top of data from the device.
>>
>> * When CONFIG_DMA_CACHE_RWFO is disabled, a cache flush on one CPU
>> is not seen by the other core(s), leading to inconsistent contents
>> accross the system.
>>
>> As a consequence, neither configuration is actually safe to use in a
>> general-purpose kernel that is used on both MPCore systems and ARM1176
>> with prefetching enabled.
>>
>> We could add further workarounds to make the behavior more dynamic based
>> on the system, but realistically, there are close to zero remaining
>> users on any ARM11MPCore anyway, and nobody seems too interested in it,
>> compared to the more popular ARM1176 used in BMC2835 and AST2500.
>>
>> The Oxnas platform has some minimal support in OpenWRT, but most of the
>> drivers and dts files never made it into the mainline kernel, while the
>> Arm Versatile/Realview platform mainly serves as a reference system but
>> is not necessary to be kept working once all other ARM11MPCore are gone.
>
> Acked-by: Neil Armstrong <neil.armstrong@linaro.org>
>
> It's sad but it's the reality, there's no chance full OXNAS support will
> ever come upstream and no real work has been done for years.
>
> I think OXNAS support can be programmed for removal for next release,
> it would need significant work to rework current support to make it acceptable
> before trying to upstream missing bits anyway.
Ok, thanks for your reply!
To clarify, do you think we should plan for removal after the next
stable release (6.3, removed in 6.4), or after the next LTS
release (probably 6.6, removed in 6.7)? As far as I understand,
the next OpenWRT release (23.x) will be based on linux-5.15,
and the one after that (24.x) would likely still use 6.1, unless
they skip an LTS kernel.
Arnd
next prev parent reply other threads:[~2023-03-30 10:04 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-27 12:12 [PATCH 00/21] dma-mapping: unify support for cache flushes Arnd Bergmann
2023-03-27 12:12 ` [PATCH 01/21] openrisc: dma-mapping: flush bidirectional mappings Arnd Bergmann
2023-03-27 12:12 ` [PATCH 02/21] xtensa: dma-mapping: use normal cache invalidation rules Arnd Bergmann
2023-03-27 15:42 ` Max Filippov
2023-03-27 12:12 ` [PATCH 03/21] sparc32: flush caches in dma_sync_*for_device Arnd Bergmann
2023-03-27 12:13 ` [PATCH 04/21] microblaze: dma-mapping: skip extra DMA flushes Arnd Bergmann
2023-03-27 12:13 ` [PATCH 05/21] powerpc: dma-mapping: split out cache operation logic Arnd Bergmann
2023-03-27 12:13 ` [PATCH 06/21] powerpc: dma-mapping: minimize for_cpu flushing Arnd Bergmann
2023-03-27 12:56 ` Christophe Leroy
2023-03-27 13:02 ` Arnd Bergmann
2023-03-27 12:13 ` [PATCH 07/21] powerpc: dma-mapping: always clean cache in _for_device() op Arnd Bergmann
2023-03-27 12:13 ` [PATCH 08/21] riscv: dma-mapping: only invalidate after DMA, not flush Arnd Bergmann
2023-03-29 20:48 ` Conor Dooley
2023-03-30 7:10 ` Arnd Bergmann
2023-03-29 21:51 ` Jessica Clarke
2023-03-30 12:59 ` Lad, Prabhakar
2023-04-19 14:22 ` Palmer Dabbelt
2023-03-27 12:13 ` [PATCH 09/21] riscv: dma-mapping: skip invalidation before bidirectional DMA Arnd Bergmann
2023-03-29 20:16 ` Conor Dooley
2023-03-30 13:26 ` Lad, Prabhakar
2023-04-19 14:22 ` Palmer Dabbelt
2023-05-05 5:47 ` Guo Ren
2023-05-05 13:18 ` Arnd Bergmann
2023-05-06 7:25 ` Guo Ren
2023-05-06 7:53 ` Arnd Bergmann
2023-03-27 12:13 ` [PATCH 10/21] csky: dma-mapping: skip invalidating before DMA from device Arnd Bergmann
2023-03-27 13:37 ` Guo Ren
2023-03-27 12:13 ` [PATCH 11/21] mips: dma-mapping: skip invalidating before bidirectional DMA Arnd Bergmann
2023-03-27 12:13 ` [PATCH 12/21] mips: dma-mapping: split out cache operation logic Arnd Bergmann
2023-03-27 12:13 ` [PATCH 13/21] arc: dma-mapping: skip invalidating before bidirectional DMA Arnd Bergmann
2023-04-02 6:52 ` Vineet Gupta
2023-04-04 8:27 ` Shahab Vahedi
2023-04-06 9:01 ` Shahab Vahedi
2023-03-27 12:13 ` [PATCH 14/21] parisc: dma-mapping: use regular flush/invalidate ops Arnd Bergmann
2023-03-27 12:13 ` [PATCH 15/21] ARM: dma-mapping: always invalidate WT caches before DMA Arnd Bergmann
2023-03-31 9:01 ` Linus Walleij
2023-03-31 9:07 ` Russell King (Oracle)
2023-03-31 9:35 ` Russell King (Oracle)
2023-03-31 10:38 ` Arnd Bergmann
2023-03-31 11:08 ` Russell King (Oracle)
2023-03-31 12:32 ` Arnd Bergmann
2023-03-27 12:13 ` [PATCH 16/21] ARM: dma-mapping: bring back dmac_{clean,inv}_range Arnd Bergmann
2023-03-27 13:10 ` Russell King (Oracle)
2023-03-27 12:13 ` [PATCH 17/21] ARM: dma-mapping: use arch_sync_dma_for_{device,cpu}() internally Arnd Bergmann
2023-03-31 9:10 ` Linus Walleij
2023-03-31 12:48 ` Arnd Bergmann
2023-03-27 12:13 ` [PATCH 18/21] ARM: drop SMP support for ARM11MPCore Arnd Bergmann
2023-03-30 7:48 ` Neil Armstrong
2023-03-30 10:03 ` Arnd Bergmann [this message]
2023-03-30 16:40 ` Neil Armstrong
2023-03-30 8:12 ` Linus Walleij
2023-03-30 11:51 ` Ard Biesheuvel
2023-03-31 17:09 ` Catalin Marinas
2023-03-27 12:13 ` [PATCH 19/21] ARM: dma-mapping: use generic form of arch_sync_dma_* helpers Arnd Bergmann
2023-03-27 12:13 ` [PATCH 20/21] ARM: dma-mapping: split out arch_dma_mark_clean() helper Arnd Bergmann
2023-03-27 12:48 ` Robin Murphy
2023-03-31 14:00 ` Arnd Bergmann
2023-03-31 15:12 ` Robin Murphy
2023-03-31 17:20 ` Arnd Bergmann
2023-03-27 15:01 ` Russell King (Oracle)
2023-03-31 14:06 ` Arnd Bergmann
2023-03-31 15:54 ` Russell King (Oracle)
2023-07-03 7:54 ` Geert Uytterhoeven
2023-07-06 14:11 ` Christoph Hellwig
2023-03-27 12:13 ` [PATCH 21/21] dma-mapping: replace custom code with generic implementation Arnd Bergmann
2023-03-27 22:25 ` Christoph Hellwig
2023-03-31 13:04 ` Arnd Bergmann
2023-03-30 14:06 ` Lad, Prabhakar
2023-04-13 12:13 ` Biju Das
2023-04-13 12:51 ` Arnd Bergmann
2023-06-27 16:52 ` Geert Uytterhoeven
2023-03-31 16:53 ` [PATCH 00/21] dma-mapping: unify support for cache flushes Catalin Marinas
2023-03-31 20:27 ` Arnd Bergmann
2023-05-25 7:46 ` Lad, Prabhakar
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