From: Conor Dooley <conor@kernel.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: "Palmer Dabbelt" <palmer@dabbelt.com>,
Prabhakar <prabhakar.csengg@gmail.com>,
"Conor.Dooley" <conor.dooley@microchip.com>,
"Andrew Jones" <ajones@ventanamicro.com>,
"Albert Ou" <aou@eecs.berkeley.edu>,
"Anup Patel" <apatel@ventanamicro.com>,
"Atish Patra" <atishp@rivosinc.com>,
"Biju Das" <biju.das.jz@bp.renesas.com>,
devicetree@vger.kernel.org,
"Geert Uytterhoeven" <geert@linux-m68k.org>,
guoren <guoren@kernel.org>,
"Christoph Hellwig" <hch@infradead.org>,
"Heiko Stübner" <heiko@sntech.de>,
"Jisheng Zhang" <jszhang@kernel.org>,
krzysztof.kozlowski+dt@linaro.org, linux-kernel@vger.kernel.org,
Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
linux-riscv@lists.infradead.org,
"Magnus Damm" <magnus.damm@gmail.com>,
"Nathan Chancellor" <nathan@kernel.org>,
"Paul Walmsley" <paul.walmsley@sifive.com>,
"Philipp Tomsich" <philipp.tomsich@vrull.eu>,
"Lad, Prabhakar" <prabhakar.mahadev-lad.rj@bp.renesas.com>,
"Rob Herring" <robh+dt@kernel.org>,
"Samuel Holland" <samuel@sholland.org>,
soc@kernel.org, "Daire McNamara" <daire.mcnamara@microchip.com>
Subject: Re: [RFC v5.1 9/9] [DON'T APPLY] cache: sifive-ccache: add cache flushing capability
Date: Wed, 4 Jan 2023 11:56:40 +0000 [thread overview]
Message-ID: <Y7VpeK48nslxklkF@spud> (raw)
In-Reply-To: <43aee000-5b89-4d94-98d2-b37b1a18a83e@app.fastmail.com>
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Hey Arnd,
On Wed, Jan 04, 2023 at 11:19:44AM +0100, Arnd Bergmann wrote:
> On Wed, Jan 4, 2023, at 10:23, Conor Dooley wrote:
> >>Right, no need to touch the existing file as part of this series,
> >>it probably just gets in the way of defining a good interface here.
> >
> > Sure. Can leave it where it was & I'll sort it out later when it's
> > errata etc get added.
> >
> > Btw, would you mind pointing out where you wanted to have that if/else
> > you mentioned on IRC?
>
> I meant replacing both of the runtime patching indirections in
> arch_sync_dma_for_device(). At the moment, this function calls
> ALT_CMO_OP(), which is patched to either call the ZICBOM or the
> THEAD variant, and if I read this right you add a third case
> there with another level of indirection using static_branch.
Yah, pretty much.
> I would try to replace both of these indirections and instead
> handle it all from C code in arch_sync_dma_for_device() directly,
> for the purpose of readability and maintainability.
> static inline void dma_cache_clean(void *vaddr, size_t size)
> {
> if (!cache_maint_ops.clean)
> zicbom_cache_clean(vaddr, size, riscv_cbom_block_size);
And I figure that this function is effectively a wrapper around ALT_CMO_OP()?
> else
> cache_maint_ops.clean(vaddr, size, riscv_cbom_block_size);
And this one gets registered by the driver using an interface like the
one I already proposed, just with the cache_maint_ops struct expanded?
Extrapolating, with these changes having an errata would not even be
needed in order to do cache maintenance.
Since the ALT_CMO_OP() version would only be used inside
zicbom_cache_clean(), assuming I understood correctly, a driver could
just register cache_maint_ops for a given platform without having to
muck around with errata.
If so, that seems like a distinct improvement over my suggestion & gets
around the thing I mentioned in 0/9 about a shared case in the
alternative application code.
Again, assuming I understood correctly, I like this a lot.
> }
>
> void arch_sync_dma_for_device(phys_addr_t paddr, size_t size,
> enum dma_data_direction dir)
> {
> void *vaddr = phys_to_virt(paddr);
>
> switch (dir) {
> case DMA_TO_DEVICE:
> case DMA_FROM_DEVICE:
> dma_cache_clean(vaddr, size);
> break;
> case DMA_BIDIRECTIONAL:
> dma_cache_flush(vaddr, size);
> break;
> default:
> break;
> }
> }
>
> which then makes it very clear what the actual code path
> is, while leaving the zicbom case free of indirect function
> calls. You can still use a static_branch() to optimize the
> conditional, but I would try to avoid any extra indirection
> levels or errata checks.
The other thing that I like about this is we can then remove the various
calls to ALT_CMO_OP() that are scattered around arch/riscv now & replace
them with functions that have more understandable names.
Thanks Arnd!
Conor.
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next prev parent reply other threads:[~2023-01-04 15:11 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-12 11:54 [PATCH v5 0/6] AX45MP: Add support to non-coherent DMA Prabhakar
2022-12-12 11:55 ` [PATCH v5 1/6] riscv: asm: alternative-macros: Introduce ALTERNATIVE_3() macro Prabhakar
2022-12-12 12:32 ` Heiko Stuebner
2022-12-13 17:21 ` Geert Uytterhoeven
2022-12-13 17:49 ` Lad, Prabhakar
2022-12-14 14:34 ` Andrew Jones
2022-12-17 21:41 ` Conor Dooley
2022-12-19 11:15 ` Lad, Prabhakar
2022-12-19 16:22 ` Conor Dooley
2022-12-19 16:24 ` Lad, Prabhakar
2022-12-12 11:55 ` [PATCH v5 2/6] riscv: asm: vendorid_list: Add Andes Technology to the vendors list Prabhakar
2022-12-12 11:55 ` [PATCH v5 3/6] riscv: errata: Add Andes alternative ports Prabhakar
2022-12-17 21:19 ` Conor Dooley
2022-12-19 11:19 ` Lad, Prabhakar
2022-12-19 16:20 ` Conor Dooley
2022-12-21 0:31 ` Lad, Prabhakar
2022-12-12 11:55 ` [PATCH v5 4/6] riscv: mm: dma-noncoherent: Pass direction and operation to ALT_CMO_OP() Prabhakar
2022-12-13 17:14 ` Geert Uytterhoeven
2022-12-13 17:57 ` Lad, Prabhakar
2022-12-17 20:52 ` Conor Dooley
2022-12-19 11:21 ` Lad, Prabhakar
2022-12-12 11:55 ` [PATCH v5 5/6] dt-bindings: cache: r9a07g043f-l2-cache: Add DT binding documentation for L2 cache controller Prabhakar
2022-12-12 17:28 ` Rob Herring
2022-12-12 11:55 ` [PATCH v5 6/6] soc: renesas: Add L2 cache management for RZ/Five SoC Prabhakar
2022-12-15 10:34 ` Geert Uytterhoeven
2022-12-15 11:03 ` Lad, Prabhakar
2022-12-15 11:10 ` Geert Uytterhoeven
2022-12-15 17:46 ` Lad, Prabhakar
2022-12-15 19:54 ` Conor Dooley
2022-12-15 20:17 ` Geert Uytterhoeven
2022-12-15 20:32 ` Conor Dooley
2022-12-15 21:40 ` Palmer Dabbelt
2022-12-16 7:02 ` Christoph Hellwig
2022-12-16 16:32 ` Palmer Dabbelt
2022-12-16 20:04 ` Arnd Bergmann
2022-12-17 22:52 ` Conor Dooley
2022-12-19 12:43 ` Lad, Prabhakar
2022-12-19 16:08 ` Conor Dooley
2022-12-29 14:05 ` Arnd Bergmann
2022-12-29 14:42 ` Conor Dooley
2023-01-03 21:03 ` [RFC v5.1 0/9] Generic function based cache management operations (was Re: [PATCH v5 6/6] soc: renesas: Add L2 cache management for RZ/Five SoC) Conor Dooley
2023-01-03 21:03 ` [RFC v5.1 1/9] riscv: asm: alternative-macros: Introduce ALTERNATIVE_3() macro Conor Dooley
2023-01-03 21:03 ` [RFC v5.1 2/9] riscv: asm: vendorid_list: Add Andes Technology to the vendors list Conor Dooley
2023-01-03 21:03 ` [RFC v5.1 3/9] riscv: errata: Add Andes alternative ports Conor Dooley
2023-01-03 21:03 ` [RFC v5.1 4/9] riscv: mm: dma-noncoherent: Pass direction and operation to ALT_CMO_OP() Conor Dooley
2023-01-03 21:03 ` [RFC v5.1 5/9] dt-bindings: cache: r9a07g043f-l2-cache: Add DT binding documentation for L2 cache controller Conor Dooley
2023-01-03 21:03 ` [RFC v5.1 6/9] cache,soc: Move SiFive CCache driver & create drivers/cache Conor Dooley
2023-01-04 9:50 ` Ben Dooks
2023-01-04 10:18 ` Conor Dooley
2023-01-03 21:03 ` [RFC v5.1 7/9] RISC-V: create a function based cache management interface Conor Dooley
2023-01-03 21:04 ` [RFC v5.1 8/9] soc: renesas: Add L2 cache management for RZ/Five SoC Conor Dooley
2023-01-03 21:04 ` [RFC v5.1 9/9] [DON'T APPLY] cache: sifive-ccache: add cache flushing capability Conor Dooley
2023-01-03 21:25 ` Palmer Dabbelt
2023-01-03 21:28 ` Arnd Bergmann
2023-01-04 0:00 ` Conor Dooley
2023-01-04 8:17 ` Arnd Bergmann
2023-01-04 9:23 ` Conor Dooley
2023-01-04 10:19 ` Arnd Bergmann
2023-01-04 11:56 ` Conor Dooley [this message]
2023-01-04 12:18 ` Arnd Bergmann
2023-01-04 13:20 ` Conor Dooley
2023-01-04 14:15 ` Arnd Bergmann
2023-01-04 9:45 ` Ben Dooks
2023-01-04 9:57 ` Conor Dooley
2022-12-17 21:35 ` [PATCH v5 6/6] soc: renesas: Add L2 cache management for RZ/Five SoC Conor Dooley
2022-12-28 3:16 ` Samuel Holland
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