iommu/arm-smmu: fix a signedness bug

Unsigned char is never equal to -1.

Cc: <stable@vger.kernel.org>
Tested-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index f417e89e1e7e..7243af3b891f 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -377,6 +377,7 @@ struct arm_smmu_cfg {
         u32                             cbar;
         pgd_t                           *pgd;
 };
+#define INVALID_IRPTNDX                 0xff
 
 #define ARM_SMMU_CB_ASID(cfg)           ((cfg)->cbndx)
 #define ARM_SMMU_CB_VMID(cfg)           ((cfg)->cbndx + 1)
@@ -840,7 +841,7 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
         if (IS_ERR_VALUE(ret)) {
                 dev_err(smmu->dev, "failed to request context IRQ %d (%u)\n",
                         root_cfg->irptndx, irq);
-                root_cfg->irptndx = -1;
+                root_cfg->irptndx = INVALID_IRPTNDX;
                 goto out_free_context;
         }
 
@@ -869,7 +870,7 @@ static void arm_smmu_destroy_domain_context(struct iommu_domain *domain)
         writel_relaxed(0, cb_base + ARM_SMMU_CB_SCTLR);
         arm_smmu_tlb_inv_context(root_cfg);
 
-        if (root_cfg->irptndx != -1) {
+        if (root_cfg->irptndx != INVALID_IRPTNDX) {
                 irq = smmu->irqs[smmu->num_global_irqs + root_cfg->irptndx];
                 free_irq(irq, domain);
         }