From: Christoph Hellwig <hch@lst.de>
To: Atish Patra <atish.patra@wdc.com>
Cc: linux-kernel@vger.kernel.org, Albert Ou <aou@eecs.berkeley.edu>,
Christoph Hellwig <hch@lst.de>,
devicetree@vger.kernel.org, Dmitry Vyukov <dvyukov@google.com>,
Frank Rowand <frowand.list@gmail.com>,
Guo Ren <guoren@linux.alibaba.com>,
iommu@lists.linux-foundation.org,
linux-riscv@lists.infradead.org,
Marek Szyprowski <m.szyprowski@samsung.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Rob Herring <robh+dt@kernel.org>,
Robin Murphy <robin.murphy@arm.com>,
Tobias Klauser <tklauser@distanz.ch>
Subject: Re: [RFC 3/5] dma-mapping: Enable global non-coherent pool support for RISC-V
Date: Mon, 26 Jul 2021 09:00:30 +0200 [thread overview]
Message-ID: <20210726070030.GB9035@lst.de> (raw)
In-Reply-To: <20210723214031.3251801-4-atish.patra@wdc.com>
On Fri, Jul 23, 2021 at 02:40:29PM -0700, Atish Patra wrote:
> Currently, linux,dma-default is used to reserve a global non-coherent pool
> to allocate memory for dma operations. This can be useful for RISC-V as
> well as the ISA specification doesn't specify a method to modify PMA
> attributes or page table entries to define non-cacheable area yet.
> A non-cacheable memory window is an alternate options for vendors to
> support non-coherent devices.
Please explain why you do not want to use the simply non-cachable
window support using arch_dma_set_uncached as used by mips, niops2 and
xtensa.
> +static int __dma_init_global_coherent(phys_addr_t phys_addr, dma_addr_t device_addr, size_t size)
> {
> struct dma_coherent_mem *mem;
>
> - mem = dma_init_coherent_memory(phys_addr, phys_addr, size, true);
> + if (phys_addr == device_addr)
> + mem = dma_init_coherent_memory(phys_addr, device_addr, size, true);
> + else
> + mem = dma_init_coherent_memory(phys_addr, device_addr, size, false);
Nak. The phys_addr != device_addr support is goign away. This needs
to be filled in using dma-ranges property hanging of the struct device.
next prev parent reply other threads:[~2021-07-26 7:00 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-23 21:40 [RFC 0/5] Support non-coherent DMA on RISC-V using a global pool Atish Patra
2021-07-23 21:40 ` [RFC 1/5] RISC-V: Implement arch_sync_dma* functions Atish Patra
2021-07-26 6:56 ` Christoph Hellwig
2021-07-26 21:52 ` Atish Patra
2021-09-11 9:37 ` Guo Ren
2021-08-17 1:48 ` Guo Ren
2021-08-17 3:24 ` Atish Patra
2021-08-17 6:28 ` Guo Ren
2021-07-23 21:40 ` [RFC 2/5] of: Move of_dma_get_range to of_address.h Atish Patra
2021-07-23 21:40 ` [RFC 3/5] dma-mapping: Enable global non-coherent pool support for RISC-V Atish Patra
2021-07-25 22:29 ` Rob Herring
2021-07-26 7:00 ` Christoph Hellwig [this message]
2021-07-26 22:47 ` Atish Patra
2021-07-27 8:52 ` Christoph Hellwig
2021-08-02 18:22 ` Atish Patra
2021-07-23 21:40 ` [RFC 4/5] dma-direct: Allocate dma pages directly if global pool allocation fails Atish Patra
2021-07-26 7:01 ` Christoph Hellwig
2021-07-23 21:40 ` [RFC 5/5] RISC-V: Support a new config option for non-coherent DMA Atish Patra
2021-07-29 4:30 ` [RFC 0/5] Support non-coherent DMA on RISC-V using a global pool Palmer Dabbelt
2021-07-29 6:19 ` Atish Patra
2021-08-17 1:37 ` Guo Ren
2021-08-17 3:28 ` Atish Patra
2021-08-17 6:42 ` Guo Ren
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