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

Niklas Cassel
2025-01-31T18:31:48Z

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(-)

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2.48.1