linux-kernel - Re: [PATCH 04/13] iommu/arm-smmu: Clean up bus_set

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Message-ID: <5ae51610-5027-777e-36e3-7bdb92e00752@arm.com>
Date:   Wed, 20 Apr 2022 17:05:03 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Will Deacon <will@...nel.org>
Cc:     joro@...tes.org, iommu@...ts.linux-foundation.org,
        sven@...npeter.dev, robdclark@...il.com, m.szyprowski@...sung.com,
        baolu.lu@...ux.intel.com, yong.wu@...iatek.com,
        mjrosato@...ux.ibm.com, gerald.schaefer@...ux.ibm.com,
        zhang.lyra@...il.com, thierry.reding@...il.com, vdumpa@...dia.com,
        jean-philippe@...aro.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/13] iommu/arm-smmu: Clean up bus_set_iommu()

On 2022-04-19 15:40, Will Deacon wrote:
> On Thu, Apr 14, 2022 at 01:42:33PM +0100, Robin Murphy wrote:
>> Stop calling bus_set_iommu() since it's now unnecessary. With device
>> probes now replayed for every IOMMU instance registration, the whole
>> sorry ordering workaround for legacy DT bindings goes too, hooray!
> 
> Ha, I hope you tested this!

Oh alright then, since it's you... :)

I've hacked up a Juno DT with the old bindings, and (after needing a 
while to remember that they're fundamentally incompatible with 
disable_bypass), can confirm that with my whole dev branch including 
this series applied, it boots and creates IOMMU groups as expected. I 
then made the mistake of trying without the branch to check whether the 
squawks from iommu_setup_dma_ops() were new or not, and... well... plain 
rc3 doesn't even boot on the same setup - it's somehow blowing up in the 
failure cleanup path of iommu_bus_init(), apparently calling 
iommu_release_device() on something where dev->iommu->iommu_dev is NULL, 
for reasons that are far from clear and I'm not sure I can really be 
bothered to debug further... :/

Cheers,
Robin.

>> Signed-off-by: Robin Murphy <robin.murphy@....com>
>> ---
>>   drivers/iommu/arm/arm-smmu/arm-smmu.c | 84 +--------------------------
>>   1 file changed, 2 insertions(+), 82 deletions(-)
> 
> Assuming it works,
> 
> Acked-by: Will Deacon <will@...nel.org>
> 
> Will