[PATCH V8 07/11] iommu: of: Handle IOMMU lookup failure with deferred probing or error

[sricharan@codeaurora.org (Sricharan R)]

Hi Magnus,

<snip..>

>> 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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