[PATCH 2/4] iommu/exynos: fix the enable sequence for no-block SysMMUs

[Markuss Broks via B4 Relay <devnull+markuss.broks.gmail.com@kernel.org>]

From: Markuss Broks <markuss.broks@gmail.com>

__sysmmu_enable() writes CTRL_BLOCK before programming CFG, the page
table base and the VM registers. CTRL_BLOCK has the enable bit set,
so on hardware without BLOCK mode this write immediately starts
translation with whatever FLPT base the registers hold: reset values
on the first enable, a stale page table on re-enable. A master that
is already emitting traffic at that point gets its transactions
translated through that garbage.

Keep the MMU disabled while it is being programmed on such hardware;
the final CTRL_ENABLE write then brings it up with a consistent
configuration in one step, which is also the same as the vendor driver
sequence.

Signed-off-by: Markuss Broks <markuss.broks@gmail.com>
---
 drivers/iommu/exynos-iommu.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/exynos-iommu.c b/drivers/iommu/exynos-iommu.c
index 0319da9fd831..a3a59d8a4cf1 100644
--- a/drivers/iommu/exynos-iommu.c
+++ b/drivers/iommu/exynos-iommu.c
@@ -655,7 +655,12 @@ static void __sysmmu_enable(struct sysmmu_drvdata *data)
 	__sysmmu_enable_clocks(data);
 
 	spin_lock_irqsave(&data->lock, flags);
-	writel(CTRL_BLOCK, data->sfrbase + REG_MMU_CTRL);
+	/*
+	 * On no-block hardware CTRL_BLOCK acts as a plain enable; keep the
+	 * MMU disabled until it is fully programmed.
+	 */
+	if (!data->no_block)
+		writel(CTRL_BLOCK, data->sfrbase + REG_MMU_CTRL);
 	__sysmmu_init_config(data);
 	__sysmmu_set_ptbase(data, data->pgtable);
 	__sysmmu_enable_vid(data);

-- 
2.55.0