Hi Magnus,

<snip..>

quoted

Magnus, do you have a suggestion?

Thanks for your efforts guys!

I've recently been working on up-porting the IPMMU patches and
addressing review comments. Now with my local driver stack on top of
v4.12-rc (a95cfad) I did not notice these issues initially since I
only tested devices with IPMMU enabled. Once these issues were pointed
out to me by Geert I have now reproduced the 64-bit ARM specific ones
on r8a7796 Salvator-X.

On my r8a7796 platform I'm using the following IOMMU and DMA Engine devices:

IOMMU device IPMMU-DS0 - Connected to SYS-DMAC0
IOMMU device IPMMU-DS1 - Connected to SYS-DMAC1 and SYS-DMAC2
IOMMU device IPMMU-MM - Root device serving IPMMU-DS0 and IPMMU-DS1

For testing the serial port SCIF1 is used with DMA Engine devices
SYS-DMAC1 or SYS-DMAC2.

The software environment is configured as follows:
- The DTS comes with all devices above enabled except IPMMU-DS0 which
comes with status = "disabled".
- The IPMMU driver is during run time only allowing use of SYS-DMAC2.
For other devices ->of_xlate() returns -ENODEV.

The above used to work just fine with v4.11 or earlier.

My observations for v4.12-rc:

1) Default state for a95cfad

The devices SYS-DMAC0 and SYS-DMAC1 will never probe. However SYS-DMAC2 is fine.

2) After applying "[PATCH] iommu: of: Fix check for returning EPROBE_DEFER" [1]

This fixes SYS-DMAC0 that now probes and operates without IPMMU-DS0 as
expected. Same as v4.11 or earlier.

3) After also applying "[PATCH] of: iommu: Ignore all errors except
EPROBE_DEFER" [2]

This fixes SYS-DMAC1 that now probes and operates without IPMMU-DS1 as
expected. Same as v4.11 or earlier.

With fix [1] and [2] things seem back to normal. Unless I'm mistaken

Thanks, will use this as your Tested-by.

Regards,
 Sricharan

it also seems that [1] allows me to drop the similar patch "[PATCH/RFC
v2 1/4] iommu/of: Skip IOMMU devices disabled in DT".

Thanks for your help.

Cheers,

/ magnus


[1] https://lkml.org/lkml/2017/5/16/25
[2] https://www.spinics.net/lists/arm-kernel/msg581485.html
[3] https://patchwork.kernel.org/patch/9540605/

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