From: Christoph Hellwig <hch@lst.de>
To: Conor Dooley <conor@kernel.org>
Cc: Maxim Kochetkov <fido_max@inbox.ru>,
Christoph Hellwig <hch@lst.de>,
Jiaxun Yang <jiaxun.yang@flygoat.com>,
linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
robh@kernel.org, mpe@ellerman.id.au, aou@eecs.berkeley.edu,
palmer@dabbelt.com, paul.walmsley@sifive.com
Subject: Re: [PATCH 1/1] riscv: set ARCH_DMA_DEFAULT_COHERENT if RISCV_DMA_NONCOHERENT is not set
Date: Fri, 22 Dec 2023 16:04:17 +0100 [thread overview]
Message-ID: <20231222150417.GA23363@lst.de> (raw)
In-Reply-To: <20231222-outburst-spoiling-75082a7826dd@spud>
On Fri, Dec 22, 2023 at 02:54:19PM +0000, Conor Dooley wrote:
> > of_dma_is_coherent() affects only DT devices. And we can override it with
> > "dma-coherent"/"dma-noncoherent". ACPI devices can specify by
> > "attr == DEV_DMA_COHERENT". But all other devices (platform_device, usb,
>
> I would have expected that usb devices "inherit" the value from the usb
> controller whose bus they are on. Similarly, platform devices are on a
> bus that should be marked as non-coherent if that is the case.
> Christoph certainly knows better how things operate here however.
usb is not a DMAable devices, you need to use the USB layer helpers
that call the DMA API on the host controller's device. platform_device
must have a device tree and the dma-noncoherent attribute somewhere in
the hierarchy.
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next prev parent reply other threads:[~2023-12-22 15:04 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-21 18:51 [PATCH 1/1] riscv: set ARCH_DMA_DEFAULT_COHERENT if RISCV_DMA_NONCOHERENT is not set Maxim Kochetkov
2023-12-21 20:29 ` Conor Dooley
2023-12-21 22:27 ` Jiaxun Yang
2023-12-22 4:14 ` Christoph Hellwig
2023-12-22 14:39 ` Maxim Kochetkov
2023-12-22 14:54 ` Conor Dooley
2023-12-22 15:04 ` Christoph Hellwig [this message]
2023-12-22 15:38 ` Maxim Kochetkov
2023-12-22 15:45 ` Jiaxun Yang
2023-12-22 15:53 ` Maxim Kochetkov
2023-12-22 16:01 ` Jiaxun Yang
2023-12-23 4:59 ` Christoph Hellwig
2023-12-25 6:47 ` Maxim Kochetkov
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