linux-kernel - [PATCH] powerpc/iommu: Refactor spapr_tce_platform_iommu_attach

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Date: Thu, 15 Feb 2024 07:52:32 -0600
From: Shivaprasad G Bhat <sbhat@...ux.ibm.com>
To: iommu@...ts.linux.dev, linuxppc-dev@...ts.ozlabs.org
Cc: linux-kernel@...r.kernel.org, mpe@...erman.id.au, npiggin@...il.com,
        christophe.leroy@...roup.eu, aneesh.kumar@...nel.org,
        naveen.n.rao@...ux.ibm.com, jgg@...pe.ca, jroedel@...e.de,
        tpearson@...torengineering.com, aik@....com, bgray@...ux.ibm.com,
        gregkh@...uxfoundation.org, sbhat@...ux.ibm.com,
        gbatra@...ux.vnet.ibm.com, vaibhav@...ux.ibm.com,
        venkat88@...ux.vnet.ibm.com
Subject: [PATCH] powerpc/iommu: Refactor spapr_tce_platform_iommu_attach_dev()

The patch makes the iommu_group_get() call only when using it
thereby avoiding the unnecessary get & put for domain already
being set case.

Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
Signed-off-by: Shivaprasad G Bhat <sbhat@...ux.ibm.com>
---
Changelog:
v2: https://lore.kernel.org/linux-iommu/170793401503.7491.9431631474642074097.stgit@linux.ibm.com/
 - As the v1 itself was merged, the patch was suggested to be reposted as
   cleanup/refactoring to be applied on top of v1.
 - Removed the versioning as this is actually new cleanup/refactoring.
 - Retaining the Reviewed-by as the effective new code was actually reviewed.

v1: https://lore.kernel.org/all/170784021983.6249.10039296655906636112.stgit@linux.ibm.com/
 - Minor refactor to call the iommu_get_group only if required.
 - Updated the title, description and signature(Closes/Reported-by).

 arch/powerpc/kernel/iommu.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index a9bebfd56b3b..37fae3bd89c6 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -1285,15 +1285,14 @@ spapr_tce_platform_iommu_attach_dev(struct iommu_domain *platform_domain,
 				    struct device *dev)
 {
 	struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
-	struct iommu_group *grp = iommu_group_get(dev);
 	struct iommu_table_group *table_group;
+	struct iommu_group *grp;

 	/* At first attach the ownership is already set */
-	if (!domain) {
-		iommu_group_put(grp);
+	if (!domain)
 		return 0;
-	}

+	grp = iommu_group_get(dev);
 	table_group = iommu_group_get_iommudata(grp);
 	/*
 	 * The domain being set to PLATFORM from earlier