[PATCH] iommu/rockchip: implement .flush_iotlb_all

[Will Deacon]

On Fri, Jul 10, 2026 at 06:05:13PM +1200, Jiaxing Hu wrote:
> rk_iommu invalidates the IOTLB synchronously in .unmap (via
> rk_iommu_zap_iova), so it stays consistent without a deferred .iotlb_sync
> and does not advertise IOMMU_CAP_DEFERRED_FLUSH.
> 
> It never implemented the optional .flush_iotlb_all op, though, and
> iommu_flush_iotlb_all() is a no-op when that op is absent -- so on Rockchip
> a driver that owns an rk_iommu domain and calls it to flush the whole
> domain's TLB (e.g. before reusing a mapping, without unmapping it) gets
> nothing, even though the hardware can do it: rk_iommu already issues
> ZAP_CACHE for range shootdowns.
> 
> Implement it with that same primitive: ZAP_CACHE every bank of every IOMMU
> on the domain, under the runtime-PM + clk guard already used by
> rk_iommu_zap_iova().
> 
> Found while bringing up an out-of-tree RK3576 NPU (accel/rocket) driver
> that flushes before each submit; on Rockchip that flush did nothing.
> 
> Signed-off-by: Jiaxing Hu <huhuvmb88 at gmail.com>
> ---

We tried to get rid of iommu_flush_iotlb_all() in 69e5a17511f6
("iommu: Remove useless flush from iommu_create_device_direct_mappings()")
but we had to revert that in a33bf8d8ce7e ("iommu: Restore
iommu_flush_iotlb_all()") because of a user in the MSM driver.

So I think this is the wrong direction. We should try harder to remove
the function rather than add new implementations of it. I'm assuming
you're only adding it for some out-of-tree code that calls it?

Will