Re: [PATCH v4 0/7] PCI: endpoint: Allow EPF drivers to configure the size of Resizable BARs

Niklas Cassel
2025-02-13T13:35:08Z

On Fri, Jan 31, 2025 at 07:29:49PM +0100, Niklas Cassel wrote:
> The PCI endpoint framework currently does not support resizable BARs.
>
> Add a new BAR type BAR_RESIZABLE, so that EPC drivers can support resizable
> BARs properly.
>
> For a resizable BAR, we will only allow a single supported size.
> This is by design, as we do not need/want the complexity of the host side
> resizing our resizable BAR.
>
> In the DWC driver specifically, the DWC driver currently handles resizable
> BARs using an ugly hack where a resizable BAR is force set to a fixed size
> BAR with 1 MB size if detected. This is bogus, as a resizable BAR can be
> configured to sizes other than 1 MB.
>
> With these changes, an EPF driver will be able to call pci_epc_set_bar()
> to configure a resizable BAR to an arbitrary size, just like for
> BAR_PROGRAMMABLE. Thus, DWC based EPF drivers will no longer be forced to
> a bogus 1 MB forced size for resizable BARs.
>
>
> Tested/verified on a Radxa Rock 5b (rk3588) by:
> -Modifying pci-epf-test.c to request BAR sizes that are larger than 1 MB:
> -static size_t bar_size[] = { 512, 512, 1024, 16384, 131072, 1048576 };
> +static size_t bar_size[] = { SZ_1M, SZ_1M, SZ_2M, SZ_2M, SZ_4M, SZ_4M };
> (Make sure to set CONFIG_CMA_ALIGNMENT=10 such that dma_alloc_coherent()
> calls are aligned even for allocations larger than 1 MB.)
> -Rebooting the host to make sure that the DWC EP driver configures the BARs
> correctly after receiving a link down event.
> -Modifying EPC features to configure a BAR as 64-bit, to make sure that we
> handle 64-bit BARs correctly.
> -Modifying the DWC EP driver to set a size larger than 2 GB, to make sure
> we handle BAR sizes larger than 2 GB (for 64-bit BARs) correctly.
> -Running the consecutive BAR test in pci_endpoint_test.c to make sure that
> the address translation works correctly.
>
>
> Changes since V3:
> -Picked up tags.
> -Addressed comments from Mani.
>
>
> Kind regards,
> Niklas
>
> Niklas Cassel (7):
> PCI: endpoint: Allow EPF drivers to configure the size of Resizable
> BARs
> PCI: endpoint: Add pci_epc_bar_size_to_rebar_cap()
> PCI: dwc: ep: Move dw_pcie_ep_find_ext_capability()
> PCI: dwc: endpoint: Allow EPF drivers to configure the size of
> Resizable BARs
> PCI: keystone: Describe Resizable BARs as Resizable BARs
> PCI: keystone: Specify correct alignment requirement
> PCI: dw-rockchip: Describe Resizable BARs as Resizable BARs
>
> drivers/pci/controller/dwc/pci-keystone.c | 6 +-
> .../pci/controller/dwc/pcie-designware-ep.c | 218 +++++++++++++++---
> drivers/pci/controller/dwc/pcie-dw-rockchip.c | 22 +-
> drivers/pci/endpoint/pci-epc-core.c | 31 +++
> drivers/pci/endpoint/pci-epf-core.c | 4 +
> include/linux/pci-epc.h | 5 +
> 6 files changed, 239 insertions(+), 47 deletions(-)
>
> --
> 2.48.1
>

Considering that all patches are have at least one R-b tag,
any chance this series could get picked up?

Kind regards,
Niklas