Hi, On Mon, Mar 07, 2022 at 07:34:22PM -0800, Saravana Kannan wrote: > On Mon, Mar 7, 2022 at 3:21 PM Rob Herring <robh@xxxxxxxxxx> wrote: > > > > +Saravana > > > > On Wed, Mar 02, 2022 at 10:10:53PM +0100, Paul Kocialkowski wrote: > > > In order to set their correct DMA address offset, some devices rely on > > > the device-tree interconnects property which identifies an > > > interconnect node that provides a dma-ranges property that can be used > > > to set said offset. > > > > > > Since that logic is all handled by the generic openfirmware and driver > > > code, the device-tree description could be enough to properly set > > > the offset. > > > > > > However the interconnects property is currently not marked as > > > optional, which implies that a driver for the corresponding node > > > must be loaded as a requirement. When no such driver exists, this > > > results in an endless EPROBE_DEFER which gets propagated to the > > > calling driver. This ends up in the driver never loading. > > > > > > Marking the interconnects property as optional makes it possible > > > to load the driver in that situation, since the EPROBE_DEFER return > > > code will no longer be propagated to the driver. > > > > > > There might however be undesirable consequences with this change, > > > which I do not fully grasp at this point. > > Temporary NACK till I get a bit more time to take a closer look. I > really don't like the idea of making interconnects optional. IOMMUs > and DMAs were exceptions. Also, we kinda discuss similar issues in > LPC. We had some consensus on how to handle these and I noted them all > down with a lot of details -- let me go take a look at those notes > again and see if I can send a more generic patch. > > Paul, > > Can you point to the DTS (not DTSI) file that corresponds to this? > Also, if it's a builtin kernel, I'd recommend setting > deferred_probe_timeout=1 and that should take care of it too. For the record, I also encountered this today on next-20220726 with this device: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/sun5i.dtsi#n775 The driver won't probe without fw_devlink=off Maxime
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