[PATCH v5 2/9] s390/pci: Add architecture specific resource/bus address translation

Farhan Ali
2025-11-13T18:35:23Z

On s390 today we overwrite the PCI BAR resource address to either an
artificial cookie address or MIO address. However this address is different
from the bus address of the BARs programmed by firmware. The artificial
cookie address was created to index into an array of function handles
(zpci_iomap_start). The MIO (mapped I/O) addresses are provided by firmware
but maybe different from the bus addresses. This creates an issue when trying
to convert the BAR resource address to bus address using the generic
pcibios_resource_to_bus().

Implement an architecture specific pcibios_resource_to_bus() function to
correctly translate PCI BAR resource addresses to bus addresses for s390.
Similarly add architecture specific pcibios_bus_to_resource function to do
the reverse translation.

Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
---
arch/s390/pci/pci.c | 74 +++++++++++++++++++++++++++++++++++++++
drivers/pci/host-bridge.c | 4 +--
2 files changed, 76 insertions(+), 2 deletions(-)

diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c
index c82c577db2bc..cacad02b2b7f 100644
--- a/arch/s390/pci/pci.c
+++ b/arch/s390/pci/pci.c
@@ -264,6 +264,80 @@ resource_size_t pcibios_align_resource(void *data, const struct resource *res,
return 0;
}

+void pcibios_resource_to_bus(struct pci_bus *bus, struct pci_bus_region *region,
+ struct resource *res)
+{
+ struct zpci_bus *zbus = bus->sysdata;
+ struct zpci_bar_struct *zbar;
+ struct zpci_dev *zdev;
+
+ region->start = res->start;
+ region->end = res->end;
+
+ for (int i = 0; i < ZPCI_FUNCTIONS_PER_BUS; i++) {
+ int j = 0;
+
+ zbar = NULL;
+ zdev = zbus->function[i];
+ if (!zdev)
+ continue;
+
+ for (j = 0; j < PCI_STD_NUM_BARS; j++) {
+ if (zdev->bars[j].res->start == res->start &&
+ zdev->bars[j].res->end == res->end &&
+ res->flags & IORESOURCE_MEM) {
+ zbar = &zdev->bars[j];
+ break;
+ }
+ }
+
+ if (zbar) {
+ /* only MMIO is supported */
+ region->start = zbar->val & PCI_BASE_ADDRESS_MEM_MASK;
+ if (zbar->val & PCI_BASE_ADDRESS_MEM_TYPE_64)
+ region->start |= (u64)zdev->bars[j + 1].val << 32;
+
+ region->end = region->start + (1UL << zbar->size) - 1;
+ return;
+ }
+ }
+}
+
+void pcibios_bus_to_resource(struct pci_bus *bus, struct resource *res,
+ struct pci_bus_region *region)
+{
+ struct zpci_bus *zbus = bus->sysdata;
+ struct zpci_dev *zdev;
+ resource_size_t start, end;
+
+ res->start = region->start;
+ res->end = region->end;
+
+ for (int i = 0; i < ZPCI_FUNCTIONS_PER_BUS; i++) {
+ zdev = zbus->function[i];
+ if (!zdev || !zdev->has_resources)
+ continue;
+
+ for (int j = 0; j < PCI_STD_NUM_BARS; j++) {
+ if (!zdev->bars[j].size)
+ continue;
+
+ /* only MMIO is supported */
+ start = zdev->bars[j].val & PCI_BASE_ADDRESS_MEM_MASK;
+ if (zdev->bars[j].val & PCI_BASE_ADDRESS_MEM_TYPE_64)
+ start |= (u64)zdev->bars[j + 1].val << 32;
+
+ end = start + (1UL << zdev->bars[j].size) - 1;
+
+ if (start == region->start && end == region->end) {
+ res->start = zdev->bars[j].res->start;
+ res->end = zdev->bars[j].res->end;
+ return;
+ }
+ }
+ }
+}
+
void __iomem *ioremap_prot(phys_addr_t phys_addr, size_t size,
pgprot_t prot)
{
diff --git a/drivers/pci/host-bridge.c b/drivers/pci/host-bridge.c
index afa50b446567..56d62afb3afe 100644
--- a/drivers/pci/host-bridge.c
+++ b/drivers/pci/host-bridge.c
@@ -48,7 +48,7 @@ void pci_set_host_bridge_release(struct pci_host_bridge *bridge,
}
EXPORT_SYMBOL_GPL(pci_set_host_bridge_release);

-void pcibios_resource_to_bus(struct pci_bus *bus, struct pci_bus_region *region,
+void __weak pcibios_resource_to_bus(struct pci_bus *bus, struct pci_bus_region *region,
struct resource *res)
{
struct pci_host_bridge *bridge = pci_find_host_bridge(bus);
@@ -73,7 +73,7 @@ static bool region_contains(struct pci_bus_region *region1,
return region1->start <= region2->start && region1->end >= region2->end;
}

-void pcibios_bus_to_resource(struct pci_bus *bus, struct resource *res,
+void __weak pcibios_bus_to_resource(struct pci_bus *bus, struct resource *res,
struct pci_bus_region *region)
{
struct pci_host_bridge *bridge = pci_find_host_bridge(bus);
--
2.43.0