Re: [PATCH v2 2/2] PCI: dwc: ep: Always clear IB maps on BAR update

[Niklas Cassel <cassel@kernel.org>]

On Mon, Feb 02, 2026 at 11:54:07PM +0900, Koichiro Den wrote:
> dw_pcie_ep_set_bar() currently tears down existing inbound mappings only
> when either the previous or the new struct pci_epf_bar uses submaps
> (num_submap != 0). If both the old and new mappings are BAR Match Mode,
> reprogramming the same ATU index is sufficient, so no explicit teardown
> was needed.
> 
> However, some callers may reuse the same struct pci_epf_bar instance and
> update it in place before calling set_bar() again. In that case
> ep_func->epf_bar[bar] and the passed-in epf_bar can point to the same
> object, so we cannot reliably distinguish BAR Match Mode -> BAR Match Mode
> from Address Match Mode -> BAR Match Mode. As a result, the conditional
> teardown based on num_submap becomes unreliable and existing inbound maps
> may be left active.
> 
> Call dw_pcie_ep_clear_ib_maps() unconditionally before reprogramming the
> BAR so that in-place updates are handled correctly.
> 
> This introduces a behavioral change in a corner case: if a BAR
> reprogramming attempt fails (especially for the long-standing BAR Match
> Mode -> BAR Match Mode update case), the previously programmed inbound
> mapping will already have been torn down. This should be acceptable,
> since the caller observes the error and should not use the BAR for any
> real transactions in that case.
> 
> While at it, document that the existing update parameter check is
> best-effort for in-place updates.
> 
> Fixes: cc839bef7727 ("PCI: dwc: ep: Support BAR subrange inbound mapping via Address Match Mode iATU")
> Signed-off-by: Koichiro Den <den@valinux.co.jp>
> ---

Reviewed-by: Niklas Cassel <cassel@kernel.org>