Re: [PATCH v2 2/3] PCI: tegra194: Reset BARs when running in PCIe endpoint mode

[Niklas Cassel <cassel@kernel.org>]

On Tue, Feb 10, 2026 at 11:06:04AM +0100, Niklas Cassel wrote:
> BAR_RESERVED already means disabled, it just assumes that an EPC driver
> disables all BARs by default, which is the case for:
> pci-dra7xx.c, pci-imx6.c, pci-layerscape-ep.c, pcie-artpec6.c,
> pcie-designware-plat.c, pcie-dw-rockchip.c, pcie-qcom-ep.c, pcie-rcar-gen4.c,
> pcie-stm32-ep.c, pcie-uniphier-ep.c.
> (All drivers which disables all BARs by default in the init() callback using
> dw_pcie_ep_reset_bar(). pci-epf-test will later enable all BARs that are not
> marked as BAR_RESERVED.)
> 
> That leaves: pcie-keembay.c, pci-keystone.c, pcie-tegra194.c (before my patch).
> 
> For pcie-keembay.c, this is not a problem, because BAR0, BAR2, BAR4 are marked
> as only_64bit, so pci-epf-test configure these BARs as 64-bit BARs, and thus
> BAR1, BAR3, and BAR5 will get disabled implicitly.
> 
> For pci-keystone.c, this is the only driver that is a bit weird, it marks
> BAR0 and BAR1 as reserved, but does not disable them in the init() callback.
> It seems force set BAR0 as a 32-bit BAR in the init() callback.
> 
> Thus, for all drivers except for pci-keystone.c, BAR_RESERVED does mean
> BAR_DISABLED. Feel free to send a patch that renames BAR_RESERVED to
> BAR_DISABLED.
> 
> If you send such a patch, perhaps you also want to modify the PCI endpoint
> core to call reset_bar() for all BARs marked as BAR_RESERVED/BAR_DISABLED,
> instead of each EPC driver doing so in the init() callback. I think the main
> reason why this is not done already is that thare is no reset_bar() op in
> struct pci_epc_ops epc_ops, there is only clear_bar() which clears an BAR
> enabled by an EPF driver. (So you would most likely also need to add a
> .disable_bar() op in struct pci_epc_ops epc_ops.)

Aksh (on To:),

since you have a @ti.com email, perhaps you can explain how pci-keystone.c
can pass all the pci-epf-test test cases, considering that this is the only
driver that has BARs (BAR0 and BAR1) marked as BAR_RESERVED but do not also
disable the BARs (using dw_pcie_ep_reset_bar()) in the init() callback.

Or, perhaps the simple answer is that pci-keystone.c does not pass all
pci-epf-test test cases?


Kind regards,
Niklas