Re: [PATCH] iommu/ipmmu-vmsa: Register in a sensible order

[Robin Murphy <robin.murphy@arm.com>]

On 2025-03-25 3:26 pm, Geert Uytterhoeven wrote:
> Hi Robin,
> 
> On Thu, 20 Mar 2025 at 15:41, Robin Murphy <robin.murphy@arm.com> wrote:
>> IPMMU registers almost-initialised instances, but misses assigning the
>> drvdata to make them fully functional, so initial calls back into
>> ipmmu_probe_device() are likely to fail unnecessarily. Reorder this to
>> work as it should, also pruning the long-out-of-date comment and adding
>> the missing sysfs cleanup on error for good measure.
>>
>> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
>> Fixes: bcb81ac6ae3c ("iommu: Get DT/ACPI parsing into the proper probe path")
>> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> 
> Thanks for your patch!
> 
> This fixes the
> 
>      sata_rcar ee300000.sata: late IOMMU probe at driver bind,
> something fishy here!
>      WARNING: CPU: 1 PID: 13 at drivers/iommu/iommu.c:571
> __iommu_probe_device+0x208/0x38c
> 
> I saw on Salvator-XS with R-Car M3-N.
> 
> It does not fix the second issue reported, so it is indeed too early for a
> "Closes: https://lore.kernel.org/CAMuHMdWPFnHTFeeWL2-BU8tKOL-E5K2ROOz=LLBLTJJLCK9NgA@mail.gmail.com"
> tag.

You mean .of_xlate being called multiple times? That's not an issue, 
it's normal and expected. Every time an IOMMU instance registers, it 
triggers a probe of all relevant devices which do not yet have an IOMMU 
- this has never been selective, so if a device is associated with a 
different already-registered IOMMU instance, but does not have a group 
because that instance's .probe_device rejected it, that probe also gets 
tried (and rejected) again.

The core code behaviour has been this way for a very long time, the only 
new thing is that the .of_xlate calls are now in sync with their 
corresponding .probe_device calls (and the latter are also now working 
properly again for fwspec-based ops).

Was it just that, or is there still something functionally amiss?

> Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>

Thanks!

Robin.

>> --- a/drivers/iommu/ipmmu-vmsa.c
>> +++ b/drivers/iommu/ipmmu-vmsa.c
>> @@ -1081,31 +1081,24 @@ static int ipmmu_probe(struct platform_device *pdev)
>>                  }
>>          }
>>
>> +       platform_set_drvdata(pdev, mmu);
> 
> Nit: perhaps insert a blank line here, before the comment below?
> 
>>          /*
>>           * Register the IPMMU to the IOMMU subsystem in the following cases:
>>           * - R-Car Gen2 IPMMU (all devices registered)
>>           * - R-Car Gen3 IPMMU (leaf devices only - skip root IPMMU-MM device)
>>           */
>> -       if (!mmu->features->has_cache_leaf_nodes || !ipmmu_is_root(mmu)) {
>> -               ret = iommu_device_sysfs_add(&mmu->iommu, &pdev->dev, NULL,
>> -                                            dev_name(&pdev->dev));
>> -               if (ret)
>> -                       return ret;
>> +       if (mmu->features->has_cache_leaf_nodes && ipmmu_is_root(mmu))
>> +               return 0;
>>
>> -               ret = iommu_device_register(&mmu->iommu, &ipmmu_ops, &pdev->dev);
>> -               if (ret)
>> -                       return ret;
>> -       }
>> +       ret = iommu_device_sysfs_add(&mmu->iommu, &pdev->dev, NULL, dev_name(&pdev->dev));
>> +       if (ret)
>> +               return ret;
>>
>> -       /*
>> -        * We can't create the ARM mapping here as it requires the bus to have
>> -        * an IOMMU, which only happens when bus_set_iommu() is called in
>> -        * ipmmu_init() after the probe function returns.
>> -        */
>> +       ret = iommu_device_register(&mmu->iommu, &ipmmu_ops, &pdev->dev);
>> +       if (ret)
>> +               iommu_device_sysfs_remove(&mmu->iommu);
>>
>> -       platform_set_drvdata(pdev, mmu);
>> -
>> -       return 0;
>> +       return ret;
>>   }
>>
>>   static void ipmmu_remove(struct platform_device *pdev)
> 
> Gr{oetje,eeting}s,
> 
>                          Geert
>