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

[Robin Murphy]

On 2022-09-30 20:39, Rob Herring wrote:
> 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@xxxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>
> > ---
> >
> > 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.

Indeed this was only brought to light by a patch series that Serge is 
working on, so although it's technically a fix I don't believe it's 
affecting any in-tree users yet, thus doesn't warrant backporting.

Cheers,
Robin.