linux-kernel - [RFC PATCH] iommu/arm-smmu: Add module parameter to set msi iova address

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Date:   Wed, 27 May 2020 21:33:18 +0530
From:   Srinath Mannam <srinath.mannam@...adcom.com>
To:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>
Cc:     bcm-kernel-feedback-list@...adcom.com,
        linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Srinath Mannam <srinath.mannam@...adcom.com>
Subject: [RFC PATCH] iommu/arm-smmu: Add module parameter to set msi iova address

This patch gives the provision to change default value of MSI IOVA base
to platform's suitable IOVA using module parameter. The present
hardcoded MSI IOVA base may not be the accessible IOVA ranges of platform.

Since commit aadad097cd46 ("iommu/dma: Reserve IOVA for PCIe inaccessible
DMA address"), inaccessible IOVA address ranges parsed from dma-ranges
property are reserved.

If any platform has the limitaion to access default MSI IOVA, then it can
be changed using "arm-smmu.msi_iova_base=0xa0000000" command line argument.

Signed-off-by: Srinath Mannam <srinath.mannam@...adcom.com>
---
 drivers/iommu/arm-smmu.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index 4f1a350..5e59c9d 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -72,6 +72,9 @@ static bool disable_bypass =
 module_param(disable_bypass, bool, S_IRUGO);
 MODULE_PARM_DESC(disable_bypass,
 	"Disable bypass streams such that incoming transactions from devices that are not attached to an iommu domain will report an abort back to the device and will not be allowed to pass through the SMMU.");
+static unsigned long msi_iova_base = MSI_IOVA_BASE;
+module_param(msi_iova_base, ulong, S_IRUGO);
+MODULE_PARM_DESC(msi_iova_base, "msi iova base address.");
 
 struct arm_smmu_s2cr {
 	struct iommu_group		*group;
@@ -1566,7 +1569,7 @@ static void arm_smmu_get_resv_regions(struct device *dev,
 	struct iommu_resv_region *region;
 	int prot = IOMMU_WRITE | IOMMU_NOEXEC | IOMMU_MMIO;
 
-	region = iommu_alloc_resv_region(MSI_IOVA_BASE, MSI_IOVA_LENGTH,
+	region = iommu_alloc_resv_region(msi_iova_base, MSI_IOVA_LENGTH,
 					 prot, IOMMU_RESV_SW_MSI);
 	if (!region)
 		return;
-- 
2.7.4