linux-kernel - [PATCH 5/5] drm/msm: Skip tlbinv on unmap from non-current pgtables

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Date:   Sun, 21 Aug 2022 11:19:06 -0700
From:   Rob Clark <robdclark@...il.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     linux-arm-msm@...r.kernel.org, freedreno@...ts.freedesktop.org,
        Rob Clark <robdclark@...omium.org>,
        Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Akhil P Oommen <quic_akhilpo@...cinc.com>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Chia-I Wu <olvaffe@...il.com>,
        Douglas Anderson <dianders@...omium.org>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH 5/5] drm/msm: Skip tlbinv on unmap from non-current pgtables

From: Rob Clark <robdclark@...omium.org>

We can rely on the tlbinv done by CP_SMMU_TABLE_UPDATE in this case.

Signed-off-by: Rob Clark <robdclark@...omium.org>
---
 drivers/gpu/drm/msm/adreno/a6xx_gpu.c |  6 ++++++
 drivers/gpu/drm/msm/msm_iommu.c       | 29 +++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
index c8ad8aeca777..1ba0ed629549 100644
--- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
@@ -1180,6 +1180,12 @@ static int hw_init(struct msm_gpu *gpu)
 	/* Always come up on rb 0 */
 	a6xx_gpu->cur_ring = gpu->rb[0];
 
+	/*
+	 * Note, we cannot assume anything about the state of the SMMU when
+	 * coming back from power collapse, so force a CP_SMMU_TABLE_UPDATE
+	 * on the first submit.  Also, msm_iommu_pagetable_unmap() relies on
+	 * this behavior.
+	 */
 	gpu->cur_ctx_seqno = 0;
 
 	/* Enable the SQE_to start the CP engine */
diff --git a/drivers/gpu/drm/msm/msm_iommu.c b/drivers/gpu/drm/msm/msm_iommu.c
index 94c8c09980d1..218074a58081 100644
--- a/drivers/gpu/drm/msm/msm_iommu.c
+++ b/drivers/gpu/drm/msm/msm_iommu.c
@@ -45,8 +45,37 @@ static int msm_iommu_pagetable_unmap(struct msm_mmu *mmu, u64 iova,
 		size -= 4096;
 	}
 
+	/*
+	 * A CP_SMMU_TABLE_UPDATE is always sent for the first
+	 * submit after resume, and that does a TLB invalidate.
+	 * So we can skip that if the device is not currently
+	 * powered.
+	 */
+	if (!pm_runtime_get_if_in_use(pagetable->parent->dev))
+		goto out;
+
+	/*
+	 * If we are not the current pgtables, we can rely on the
+	 * TLB invalidate done by CP_SMMU_TABLE_UPDATE.
+	 *
+	 * We'll always be racing with the GPU updating ttbr0,
+	 * but there are only two cases:
+	 *
+	 *  + either we are not the the current pgtables and there
+	 *    will be a tlbinv done by the GPU before we are again
+	 *
+	 *  + or we are.. there might have already been a tblinv
+	 *    if we raced with the GPU, but we have to assume the
+	 *    worse and do the tlbinv
+	 */
+	if (adreno_smmu->get_ttbr0(adreno_smmu->cookie) != pagetable->ttbr)
+		goto out_put;
+
 	adreno_smmu->tlb_inv_by_id(adreno_smmu->cookie, pagetable->asid);
 
+out_put:
+	pm_runtime_put(pagetable->parent->dev);
+out:
 	return (unmapped == size) ? 0 : -EINVAL;
 }
 
-- 
2.37.2