From: Christoph Hellwig <hch@lst.de>
To: Sergey Matyukevich <geomatsi@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>,
linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
Palmer Dabbelt <palmer@dabbelt.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Alexandre Ghiti <alexghiti@rivosinc.com>,
Conor Dooley <conor.dooley@microchip.com>,
Robin Murphy <robin.murphy@arm.com>,
Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>,
Geert Uytterhoeven <geert+renesas@glider.be>
Subject: Re: [PATCH] riscv: select DMA_DIRECT_REMAP by RISCV_ISA_SVPBMT and ERRATA_THEAD_MAE
Date: Fri, 17 Jan 2025 10:58:32 +0100 [thread overview]
Message-ID: <20250117095832.GB2585@lst.de> (raw)
In-Reply-To: <Z4oXF2ewizIIk1cL@curiosity>
On Fri, Jan 17, 2025 at 11:38:47AM +0300, Sergey Matyukevich wrote:
> > Please explain what this is supposed to solve, because the above
> > explanation dosn't make any sense. DMA_DIRECT_REMAP is one
> > of the implementations supporting dma coherent allocatiosn for
> > non-coherent devices. So selecting it from something that
> > just keyes off support for an extension, but not the dma
> > implementation is wrong.
>
> Now DMA_DIRECT_REMAP is selected either by Zicbom (standard) or XTheadCmo
> (vendor) RISC-V extensions.
Because they need DMA_DIRECT_REMAP to implement DMA coherent.
> However neither of them can help to implement
> DMA_DIRECT_REMAP on RISC-V. So selection of DMA_DIRECT_REMAP has been
> moved in Kconfigs to Svpbmt and XTheadMae extensions.
But Svpbmt does not imply that you even need DMA_DIRECT_REMAP.
Are you tying to solve a problem here? If so can you explain it?
next prev parent reply other threads:[~2025-01-17 9:58 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-01-16 17:29 [PATCH] riscv: select DMA_DIRECT_REMAP by RISCV_ISA_SVPBMT and ERRATA_THEAD_MAE Sergey Matyukevich
2025-01-17 7:52 ` Christoph Hellwig
2025-01-17 8:38 ` Sergey Matyukevich
2025-01-17 9:58 ` Christoph Hellwig [this message]
2025-01-17 11:01 ` Sergey Matyukevich
2025-02-17 12:23 ` Alexandre Ghiti
2025-02-20 9:48 ` Sergey Matyukevich
2025-02-26 13:58 ` Alexandre Ghiti
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