LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
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.

  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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210726070030.GB9035@lst.de \
    --to=hch@lst.de \
    --cc=aou@eecs.berkeley.edu \
    --cc=atish.patra@wdc.com \
    --cc=devicetree@vger.kernel.org \
    --cc=dvyukov@google.com \
    --cc=frowand.list@gmail.com \
    --cc=guoren@linux.alibaba.com \
    --cc=iommu@lists.linux-foundation.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-riscv@lists.infradead.org \
    --cc=m.szyprowski@samsung.com \
    --cc=palmer@dabbelt.com \
    --cc=paul.walmsley@sifive.com \
    --cc=robh+dt@kernel.org \
    --cc=robin.murphy@arm.com \
    --cc=tklauser@distanz.ch \
    --subject='Re: [RFC 3/5] dma-mapping: Enable global non-coherent pool support for RISC-V' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).