Re: [PATCH 1/7] OF: Retire dma-ranges mask workaround

From: Rob Herring <robh+dt@kernel.org>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Joerg Roedel <joro@8bytes.org>, Christoph Hellwig <hch@lst.de>,
	Vineet Gupta <vgupta@kernel.org>,
	 Russell King <linux@armlinux.org.uk>,
	Catalin Marinas <catalin.marinas@arm.com>,
	 Will Deacon <will@kernel.org>,
	Huacai Chen <chenhuacai@kernel.org>,
	WANG Xuerui <kernel@xen0n.name>,
	 Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
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	 Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	 Lorenzo Pieralisi <lpieralisi@kernel.org>,
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	 Sudeep Holla <sudeep.holla@arm.com>,
	"K. Y. Srinivasan" <kys@microsoft.com>,
	 Haiyang Zhang <haiyangz@microsoft.com>,
	Wei Liu <wei.liu@kernel.org>,  Dexuan Cui <decui@microsoft.com>,
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	 linux-arm-kernel@lists.infradead.org,
	linux-acpi@vger.kernel.org,  iommu@lists.linux.dev,
	devicetree@vger.kernel.org
Subject: Re: [PATCH 1/7] OF: Retire dma-ranges mask workaround
Date: Thu, 30 Nov 2023 08:46:36 -0600	[thread overview]
Message-ID: <CAL_JsqK_StOWTOBCR6OaAqu63_kyVKsA46qJ4ky9iSyB-yKZ2g@mail.gmail.com> (raw)
In-Reply-To: <950378c6f39270a255452733ff2305e56fb05cc5.1701268753.git.robin.murphy@arm.com>

On Wed, Nov 29, 2023 at 11:43 AM Robin Murphy <robin.murphy@arm.com> wrote:
>
> From what I remember, the fixup adding 1 to the dma-ranges size was for
> the benefit of some early AMD Seattle DTs. Those are likely extinct by
> now, and anyone else who might have deserved to get the message has
> hopefully seen the warning in the 9 years we've had it there. The modern
> dma_range_map mechanism should happily handle odd-sized ranges with no
> ill effect, so there's little need to care anyway now. Clean it up.

The commit has a tested by for Seattle, but the series adding this was
for an issue on TI Keystone[1]. Looks like the patch adding this fixup
and warning did 2 things. It added 1 to the default mask when
'dma-ranges' was not present (which keystone needed) and added 1 if
the DT value was a mask along with the warning. It's not clear what
Seattle needed, but there was a fix to dma-ranges about a year
later[2].

I thought at some point we allowed 32-bit DTs to specify a ~0 size to
avoid having to use 2 cells to express 4G size which wouldn't have
been a warning, but I can't find any discussion on that. It would have
been earlier than 2015 I think... Anyways, there is no upstream dts
with that either, so I think we're good.

> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> ---
>  drivers/of/device.c | 16 ----------------
>  1 file changed, 16 deletions(-)

Acked-by: Rob Herring <robh@kernel.org>

[1] https://lore.kernel.org/all/1425405134-24707-1-git-send-email-m-karicheri2@ti.com/
[2] https://lore.kernel.org/all/1455162671-16044-4-git-send-email-Suravee.Suthikulpanit@amd.com/

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