Commit 8c153645 authored by Jean-Philippe Brucker's avatar Jean-Philippe Brucker Committed by Will Deacon
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iommu/arm-smmu-v3: Explain why ATS stays disabled with bypass 



The SMMU does not support enabling ATS for a bypass stream. Add a comment.

Signed-off-by: default avatarJean-Philippe Brucker <jean-philippe@linaro.org>
Link: https://lore.kernel.org/r/20230321100559.341981-1-jean-philippe@linaro.org


Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent e8d018dd

drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c

+7 −0
Original line number Diff line number Diff line
@@ -2447,6 +2447,13 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev) 


	master->domain = smmu_domain;



	/*

	 * The SMMU does not support enabling ATS with bypass. When the STE is

	 * in bypass (STE.Config[2:0] == 0b100), ATS Translation Requests and

	 * Translated transactions are denied as though ATS is disabled for the

	 * stream (STE.EATS == 0b00), causing F_BAD_ATS_TREQ and

	 * F_TRANSL_FORBIDDEN events (IHI0070Ea 5.2 Stream Table Entry).

	 */

	if (smmu_domain->stage != ARM_SMMU_DOMAIN_BYPASS)

		master->ats_enabled = arm_smmu_ats_supported(master);