A resizable BAR is different from a normal BAR in a few ways:
-The minimum size of a resizable BAR is 1 MB.
-Each BAR that is resizable has a Capability and Control register in the
Resizable BAR Capability structure.
These registers contain the supported sizes and the currently selected
size of a resizable BAR.
The supported sizes is a bitmap of the supported sizes. The selected size
is a single value that is equal to one of the supported sizes.
A resizable BAR thus has to be configured differently than a
BAR_PROGRAMMABLE BAR, which usually sets the BAR size/mask in a vendor
specific way.
The PCI endpoint framework currently does not support resizable BARs.
Add a BAR type BAR_RESIZABLE, so that an EPC driver can support resizable
BARs properly.
Note that the pci_epc_set_bar() API takes a struct pci_epf_bar which tells
the EPC driver how it wants to configure the BAR.
struct pci_epf_bar only has a single size struct member.
This means that an EPC driver will only be able to set a single supported
size. This is perfectly fine, as we do not need the complexity of allowing
a host to change the size of the BAR. If someone ever wants to support
resizing a resizable BAR, the pci_epc_set_bar() API can be extended in the
future.
With these changes, an EPC driver will be able to support resizable BARs
(we intentionally only support a single supported resizable BAR size).
Signed-off-by: Niklas Cassel <cassel@xxxxxxxxxx>
---
drivers/pci/endpoint/pci-epf-core.c | 4 ++++
include/linux/pci-epc.h | 3 +++
2 files changed, 7 insertions(+)
diff --git a/drivers/pci/endpoint/pci-epf-core.c b/drivers/pci/endpoint/pci-epf-core.c
index 50bc2892a36c..394395c7f8de 100644
--- a/drivers/pci/endpoint/pci-epf-core.c
+++ b/drivers/pci/endpoint/pci-epf-core.c
@@ -274,6 +274,10 @@ void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar,
if (size < 128)
size = 128;
+ /* According to PCIe base spec, min size for a resizable BAR is 1 MB. */
+ if (epc_features->bar[bar].type == BAR_RESIZABLE && size < SZ_1M)
+ size = SZ_1M;
+
if (epc_features->bar[bar].type == BAR_FIXED && bar_fixed_size) {
if (size > bar_fixed_size) {
dev_err(&epf->dev,
diff --git a/include/linux/pci-epc.h b/include/linux/pci-epc.h
index e818e3fdcded..e9d5ed23914f 100644
--- a/include/linux/pci-epc.h
+++ b/include/linux/pci-epc.h
@@ -188,11 +188,14 @@ struct pci_epc {
* enum pci_epc_bar_type - configurability of endpoint BAR
* @BAR_PROGRAMMABLE: The BAR mask can be configured by the EPC.
* @BAR_FIXED: The BAR mask is fixed by the hardware.
+ * @BAR_RESIZABLE: The BAR implements the PCI-SIG Resizable BAR Capability.
+ * An EPC driver can currently only set a single supported size.
* @BAR_RESERVED: The BAR should not be touched by an EPF driver.
*/
enum pci_epc_bar_type {
BAR_PROGRAMMABLE = 0,
BAR_FIXED,
+ BAR_RESIZABLE,
BAR_RESERVED,
};
--
2.47.1
