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From: ovidiu.panait@windriver.com
To: linux-kernel@vger.kernel.org, iommu@lists.linux.dev
Cc: robin.murphy@arm.com, will@kernel.org, joro@8bytes.org, jgg@ziepe.ca,
        Ovidiu Panait <ovidiu.panait@windriver.com>
Subject: [PATCH] iommu: iommu_group_alloc_default_domain: Fix ops->default_domain codepath
Date: Tue, 23 Jan 2024 18:58:29 +0200
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From: Ovidiu Panait <ovidiu.panait@windriver.com>

Since commit [1], FSL_PAMU initialization on t4240rdb board fails
with: "fsl-pamu-domain: pamu_domain_init: Can't register iommu device".

Commit [1] changed the behavior for drivers that set ops->default_domain,
as the function iommu_group_alloc_default_domain() is now called with
"req_type == IOMMU_DOMAIN_IDENTITY", rather than "req_type == 0". This
causes the following EINVAL condition to be hit during FSL_PAMU
initialization:
  ...
       if (ops->default_domain) {
               if (req_type)
                       return ERR_PTR(-EINVAL);
               return ops->default_domain;
       }
  ...

To avoid this issue when ops->default_domain != NULL, remove the check for
non-zero req_type and always return the proper default domain, as set in
the driver.

  [1] 0f6a90436a57 ("iommu: Do not use IOMMU_DOMAIN_DMA [...]")

Fixes: 0f6a90436a57 ("iommu: Do not use IOMMU_DOMAIN_DMA if CONFIG_IOMMU_DMA is not enabled")
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
---
 drivers/iommu/iommu.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 68e648b55767..8e79a074e560 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1798,11 +1798,8 @@ iommu_group_alloc_default_domain(struct iommu_group *group, int req_type)
 	 * domain. This should always be either an IDENTITY/BLOCKED/PLATFORM
 	 * domain. Do not use in new drivers.
 	 */
-	if (ops->default_domain) {
-		if (req_type)
-			return ERR_PTR(-EINVAL);
+	if (ops->default_domain)
 		return ops->default_domain;
-	}
 
 	if (req_type)
 		return __iommu_group_alloc_default_domain(group, req_type);
-- 
2.34.1