linux-kernel - Re: [PATCH v3 2/5] iommu: Resolve fwspec ops automatically

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Message-ID: <82624cf6-98ad-47df-8dcd-368117600805@arm.com>
Date: Fri, 12 Jul 2024 16:28:37 +0100
From: Robin Murphy <robin.murphy@....com>
To: Jon Hunter <jonathanh@...dia.com>, Will Deacon <will@...nel.org>,
 Joerg Roedel <joro@...tes.org>
Cc: linux-acpi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, iommu@...ts.linux.dev,
 devicetree@...r.kernel.org, Rob Herring <robh@...nel.org>,
 Saravana Kannan <saravanak@...gle.com>,
 Lorenzo Pieralisi <lpieralisi@...nel.org>, Hanjun Guo
 <guohanjun@...wei.com>, Sudeep Holla <sudeep.holla@....com>,
 "Rafael J. Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>,
 Jean-Philippe Brucker <jean-philippe@...aro.org>,
 Andy Shevchenko <andy.shevchenko@...il.com>, Yong Wu <yong.wu@...iatek.com>,
 "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH v3 2/5] iommu: Resolve fwspec ops automatically

On 12/07/2024 4:24 pm, Jon Hunter wrote:
> 
> On 12/07/2024 12:48, Robin Murphy wrote:
> 
> ...
> 
>>> I am seeing some failures on -next with some of our devices. Bisect 
>>> is pointing to this commit. Looks like the host1x device is no longer 
>>> probing successfully. I see the following ...
>>>
>>>   tegra-host1x 50000000.host1x: failed to initialize fwspec: -517
>>>   nouveau 57000000.gpu: failed to initialize fwspec: -517
>>>
>>> The probe seems to be deferred forever. The above is seen on Tegra210 
>>> but Tegra30 and Tegra194 are also having the same problem. 
>>> Interestingly it is not all devices and so make me wonder if we are 
>>> missing something on these devices? Let me know if you have any 
>>> thoughts.
>>
>> Ugh, tegra-smmu has been doing a complete nonsense this whole time - 
>> on closer inspection, it's passing the fwnode of the *client device* 
>> where it should be that of the IOMMU device :(
>>
>> I *think* it should probably just be a case of:
>>
>> -    err = iommu_fwspec_init(dev, of_fwnode_handle(dev->of_node));
>> +    err = iommu_fwspec_init(dev, of_fwnode_handle(smmu->dev->of_node));
>>
>> since smmu->dev appears to be the same one initially passed to 
>> iommu_device_register(), so it at least ought to match and work, but 
>> the SMMU device vs. MC device thing leaves me mildly wary of how 
>> correct it might be overall.
>>
>> (Also now I'm wondering why I didn't just use dev_fwnode() there...)
> 
> 
> Yes making that change in the tegra-smmu driver does fix it.

Ace, thanks for confirming! I was just writing a follow-up to say that 
I've pretty much convinced myself that this (proper diff below) should 
in fact be the right thing to do in general as well :)

Will, Joerg, would you prefer to have a standalone fix patch for the 
nvidia/tegra branch to then re-merge fwspec-ops-removal and fix up the 
conflict, or just a patch on top of fwspec-ops-removal as below?

Thanks,
Robin.

----->8-----
diff --git a/drivers/iommu/tegra-smmu.c b/drivers/iommu/tegra-smmu.c
index 4365d9936e68..7f633bb5efef 100644
--- a/drivers/iommu/tegra-smmu.c
+++ b/drivers/iommu/tegra-smmu.c
@@ -837,7 +837,7 @@ static int tegra_smmu_configure(struct tegra_smmu 
*smmu, struct device *dev,
  	const struct iommu_ops *ops = smmu->iommu.ops;
  	int err;

-	err = iommu_fwspec_init(dev, of_fwnode_handle(dev->of_node));
+	err = iommu_fwspec_init(dev, dev_fwnode(smmu->dev));
  	if (err < 0) {
  		dev_err(dev, "failed to initialize fwspec: %d\n", err);
  		return err;