IOMMU Archive on lore.kernel.org
 help / color / Atom feed
From: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
To: Christoph Hellwig <hch@lst.de>
Cc: catalin.marinas@arm.com, linux-mm@kvack.org,
	linux-riscv@lists.infradead.org, will@kernel.org,
	linux-arch@vger.kernel.org, f.fainelli@gmail.com,
	frowand.list@gmail.com, devicetree@vger.kernel.org,
	Arnd Bergmann <arnd@arndb.de>,
	marc.zyngier@arm.com, robh+dt@kernel.org,
	linux-rpi-kernel@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org, phill@raspberryi.org,
	mbrugger@suse.com, eric@anholt.net, linux-kernel@vger.kernel.org,
	iommu@lists.linux-foundation.org, wahrenst@gmx.net,
	akpm@linux-foundation.org, Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH v2 01/11] asm-generic: add dma_zone_size
Date: Mon, 26 Aug 2019 15:46:52 +0200
Message-ID: <027272c27398b950f207101a2c5dbc07a30a36bc.camel@suse.de> (raw)
In-Reply-To: <20190826070939.GD11331@lst.de>

[-- Attachment #1.1: Type: text/plain, Size: 1724 bytes --]

On Mon, 2019-08-26 at 09:09 +0200, Christoph Hellwig wrote:
> On Tue, Aug 20, 2019 at 04:58:09PM +0200, Nicolas Saenz Julienne wrote:
> > Some architectures have platform specific DMA addressing limitations.
> > This will allow for hardware description code to provide the constraints
> > in a generic manner, so as for arch code to properly setup it's memory
> > zones and DMA mask.
> 
> I know this just spreads the arm code, but I still kinda hate it.

Rob's main concern was finding a way to pass the constraint from HW definition
to arch without widening fdt's architecture specific function surface. I'd say
it's fair to argue that having a generic mechanism makes sense as it'll now
traverse multiple archs and subsystems.

I get adding globals like this is not very appealing, yet I went with it as it
was the easier to integrate with arm's code. Any alternative suggestions?

> MAX_DMA_ADDRESS is such an oddly defined concepts.  We have the mm
> code that uses it to start allocating after the dma zones, but
> I think that would better be done using a function returning
> 1 << max(zone_dma_bits, 32) or so.  Then we have about a handful
> of drivers using it that all seem rather bogus, and one of which
> I think are usable on arm64.

Is it safe to assume DMA limitations will always be a power of 2? I ask as RPi4
kinda isn't: ZONE_DMA is 0x3c000000 bytes big, I'm approximating the zone mask
to 30 as [0x3c000000 0x3fffffff] isn't defined as memory so it's unlikely that
we´ll encounter buffers there. But I don't know how it could affect mm
initialization code.

This also rules out 'zone_dma_bits' as a mechanism to pass ZONE_DMA's size from
HW definition code to arch's.


[-- Attachment #1.2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

[-- Attachment #2: Type: text/plain, Size: 156 bytes --]

_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  reply index

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-20 14:58 [PATCH v2 00/11] Raspberry Pi 4 DMA addressing support Nicolas Saenz Julienne
2019-08-20 14:58 ` [PATCH v2 01/11] asm-generic: add dma_zone_size Nicolas Saenz Julienne
2019-08-26  7:09   ` Christoph Hellwig
2019-08-26 13:46     ` Nicolas Saenz Julienne [this message]
2019-08-28  9:44       ` Nicolas Saenz Julienne
2019-08-30 14:45       ` Catalin Marinas
2019-08-30 17:24         ` Nicolas Saenz Julienne
2019-09-02 13:01           ` Christoph Hellwig
2019-08-20 14:58 ` [PATCH v2 02/11] arm: use generic dma_zone_size Nicolas Saenz Julienne
2019-08-20 14:58 ` [PATCH v2 03/11] of/fdt: add of_fdt_machine_is_compatible function Nicolas Saenz Julienne
2019-08-20 17:16   ` Rob Herring
2019-08-20 17:27     ` Nicolas Saenz Julienne
2019-08-20 14:58 ` [PATCH v2 04/11] of/fdt: add early_init_dt_get_dma_zone_size() Nicolas Saenz Julienne
2019-08-20 17:14   ` Rob Herring
2019-08-20 14:58 ` [PATCH v2 05/11] arm64: mm: use arm64_dma_phys_limit instead of calling max_zone_dma_phys() Nicolas Saenz Julienne
2019-08-20 14:58 ` [PATCH v2 06/11] arm64: rename variables used to calculate ZONE_DMA32's size Nicolas Saenz Julienne
2019-08-20 14:58 ` [PATCH v2 07/11] arm64: re-introduce max_zone_dma_phys() Nicolas Saenz Julienne
2019-08-20 14:58 ` [PATCH v2 08/11] arm64: use both ZONE_DMA and ZONE_DMA32 Nicolas Saenz Julienne
2019-08-20 14:58 ` [PATCH v2 09/11] dma-direct: turn ARCH_ZONE_DMA_BITS into a variable Nicolas Saenz Julienne
2019-08-26  7:05   ` Christoph Hellwig
2019-08-26 11:33   ` Michael Ellerman
2019-08-20 14:58 ` [PATCH v2 10/11] arm64: edit zone_dma_bits to fine tune dma-direct min mask Nicolas Saenz Julienne
2019-08-26  7:06   ` Christoph Hellwig
2019-08-26 11:08     ` Nicolas Saenz Julienne
2019-08-27  7:03       ` Petr Tesarik
2019-08-20 14:58 ` [PATCH v2 11/11] mm: refresh ZONE_DMA and ZONE_DMA32 comments in 'enum zone_type' Nicolas Saenz Julienne
2019-08-26  7:07   ` Christoph Hellwig

Reply instructions:

You may reply publically 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=027272c27398b950f207101a2c5dbc07a30a36bc.camel@suse.de \
    --to=nsaenzjulienne@suse.de \
    --cc=akpm@linux-foundation.org \
    --cc=arnd@arndb.de \
    --cc=catalin.marinas@arm.com \
    --cc=devicetree@vger.kernel.org \
    --cc=eric@anholt.net \
    --cc=f.fainelli@gmail.com \
    --cc=frowand.list@gmail.com \
    --cc=hch@lst.de \
    --cc=iommu@lists.linux-foundation.org \
    --cc=linux-arch@vger.kernel.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-riscv@lists.infradead.org \
    --cc=linux-rpi-kernel@lists.infradead.org \
    --cc=marc.zyngier@arm.com \
    --cc=mbrugger@suse.com \
    --cc=phill@raspberryi.org \
    --cc=robh+dt@kernel.org \
    --cc=robin.murphy@arm.com \
    --cc=wahrenst@gmx.net \
    --cc=will@kernel.org \
    /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

IOMMU Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-iommu/0 linux-iommu/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-iommu linux-iommu/ https://lore.kernel.org/linux-iommu \
		iommu@lists.linux-foundation.org
	public-inbox-index linux-iommu

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.linux-foundation.lists.iommu


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git