linux-kernel - Re: [PATCH v2] of: Fix "dma-ranges" handling for bus controllers

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Message-ID: <166456654423.756056.16732005186500514187.robh@kernel.org>
Date:   Fri, 30 Sep 2022 14:39:01 -0500
From:   Rob Herring <robh@...nel.org>
To:     Robin Murphy <robin.murphy@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, robh+dt@...nel.org,
        frowand.list@...il.com, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Serge Semin <Sergey.Semin@...kalelectronics.ru>
Subject: Re: [PATCH v2] of: Fix "dma-ranges" handling for bus controllers

On Thu, 29 Sep 2022 13:48:38 +0100, Robin Murphy wrote:
> Commit 951d48855d86 ("of: Make of_dma_get_range() work on bus nodes")
> relaxed the handling of "dma-ranges" for any leaf node on the assumption
> that it would still represent a usage error for the property to be
> present on a non-bus leaf node. However there turns out to be a fiddly
> case where a bus also represents a DMA-capable device in its own right,
> such as a PCIe root complex with an integrated DMA engine on its
> platform side. In such cases, "dma-ranges" translation is entirely valid
> for devices discovered behind the bus, but should not be erroneously
> applied to the bus controller device itself which operates in its
> parent's address space. Fix this by restoring the previous behaviour for
> the specific case where a device is configured via its own OF node,
> since it is logical to assume that a device should never represent its
> own parent bus.
> 
> Reported-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
> Signed-off-by: Robin Murphy <robin.murphy@....com>
> ---
> 
> v2: Fix !HAS_DMA build error
> 
>  drivers/of/address.c    | 4 +++-
>  drivers/of/device.c     | 9 ++++++++-
>  drivers/of/of_private.h | 5 +++++
>  3 files changed, 16 insertions(+), 2 deletions(-)
> 

Applied, thanks!

I assume this was not tagged with Fixes or stable because there is not 
yet a user that needs it? I didn't add it either because I'm a bit 
worried about regressions and applying this just before the merge 
window. So send it to stable later if anyone cares.

Rob