Re: [PATCH v3 4/4] PCI: dwc: Fix missing iATU setup when ECAM is enabled

Niklas Cassel
2026-01-23T10:07:31Z

On Fri, Jan 23, 2026 at 10:32:13AM +0100, Niklas Cassel wrote:
> From: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
>
> When ECAM is enabled, the driver skipped calling dw_pcie_iatu_setup()
> before configuring ECAM iATU entries. This left IO and MEM outbound
> windows unprogrammed, resulting in broken IO transactions. Additionally,
> dw_pcie_config_ecam_iatu() was only called during host initialization,
> so ECAM-related iATU entries were not restored after suspend/resume,
> leading to failures in configuration space access
>
> To resolve these issues, the ECAM iATU configuration is moved into
> dw_pcie_iatu_setup(), and dw_pcie_iatu_setup() is invoked when ECAM is
> enabled.
>
> Furthermore, error checks are added in dw_pcie_prog_outbound_atu() and
> dw_pcie_prog_inbound_atu() such that an error is returned if trying to
> program an iATU that is outside the number of iATUs provided by the
> controller.
>
> Fixes: f6fd357f7afb ("PCI: dwc: Prepare the driver for enabling ECAM mechanism using iATU 'CFG Shift Feature'")
> Reported-by: Maciej W. Rozycki <macro@orcam.me.uk>
> Closes: https://lore.kernel.org/all/alpine.DEB.2.21.2511280256260.36486@angie.orcam.me.uk/
> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
> Co-developed-by: Niklas Cassel <cassel@kernel.org>
> Signed-off-by: Niklas Cassel <cassel@kernel.org>
> ---

Unfortunately there is another difference when running the DWC driver in
ECAM mode.

pp->cfg0_io_shared (which toggles iATU index 0 between CFG and I/O space
can not be used when using ECAM, since they don't have this code that
overwrites/restores the iATU configuration, see dw_pcie_rd_other_conf()
and dw_pcie_wr_other_conf().

ECAM instead uses:
pci_generic_config_read() and pci_generic_config_write()

So we would need this squashed into this patch:

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index e65ffba6529b..bc2e08ec515e 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -990,8 +990,14 @@ static int dw_pcie_iatu_setup(struct dw_pcie_rp *pp)
* be shared between I/O space and CFG IOs, by
* temporarily reconfiguring the iATU to CFG space, in
* order to do a CFG IO, and then immediately restoring
- * it to I/O space.
+ * it to I/O space. This is only implemented when using
+ * dw_pcie_other_conf_map_bus(), which is not the case
+ * when using ECAM.
*/
+ if (pp->ecam_enabled) {
+ dev_err(pci->dev, "Cannot add outbound window for I/O\n");
+ return -ENOMEM;
+ }
pp->cfg0_io_shared = true;
}
}

If we get no further comments, perhaps Mani could squash this?

Kind regards,
Niklas