Add two tunables to ignore certain firmware-assigned resources. These

are mostly useful for debugging.
- hw.pci.clear_bars ignores all firmware-assigned ranges for BARs when
  set.
- hw.pci.clear_pcib ignores all firmware-assigned ranges for PCI-PCI
  bridge I/O windows when set.

MFC after:	1 week

2 files changed, 25 insertions, 1 deletions

diff --git a/sys/dev/pci/pci.c b/sys/dev/pci/pci.c
index 3dcd745..f1cbe6c 100644
--- a/sys/dev/pci/pci.c
+++ b/sys/dev/pci/pci.c
@@ -332,6 +332,11 @@ SYSCTL_INT(_hw_pci, OID_AUTO, usb_early_takeover, CTLFLAG_RDTUN,
 Disable this if you depend on BIOS emulation of USB devices, that is\n\
 you use USB devices (like keyboard or mouse) but do not load USB drivers");
 
+static int pci_clear_bars;
+TUNABLE_INT("hw.pci.clear_bars", &pci_clear_bars);
+SYSCTL_INT(_hw_pci, OID_AUTO, clear_bars, CTLFLAG_RDTUN, &pci_clear_bars, 0,
+    "Ignore firmware-assigned resources for BARs.");
+
 static int
 pci_has_quirk(uint32_t devid, int quirk)
 {
@@ -2851,7 +2856,7 @@ pci_add_map(device_t bus, device_t dev, int reg, struct resource_list *rl,
 	flags = RF_ALIGNMENT_LOG2(mapsize);
 	if (prefetch)
 		flags |= RF_PREFETCHABLE;
-	if (basezero || base == pci_mapbase(testval)) {
+	if (basezero || base == pci_mapbase(testval) || pci_clear_bars) {
 		start = 0;	/* Let the parent decide. */
 		end = ~0ul;
 	} else {
diff --git a/sys/dev/pci/pci_pci.c b/sys/dev/pci/pci_pci.c
index 3fa3d5a..5fa886e 100644
--- a/sys/dev/pci/pci_pci.c
+++ b/sys/dev/pci/pci_pci.c
@@ -103,6 +103,12 @@ DEFINE_CLASS_0(pcib, pcib_driver, pcib_methods, sizeof(struct pcib_softc));
 DRIVER_MODULE(pcib, pci, pcib_driver, pcib_devclass, NULL, NULL);
 
 #ifdef NEW_PCIB
+SYSCTL_DECL(_hw_pci);
+
+static int pci_clear_pcib;
+TUNABLE_INT("hw.pci.clear_pcib", &pci_clear_pcib);
+SYSCTL_INT(_hw_pci, OID_AUTO, clear_pcib, CTLFLAG_RDTUN, &pci_clear_pcib, 0,
+    "Clear firmware-assigned resources for PCI-PCI bridge I/O windows.");
 
 /*
  * Is a resource from a child device sub-allocated from one of our
@@ -416,6 +422,19 @@ pcib_probe_windows(struct pcib_softc *sc)
 
 	dev = sc->dev;
 
+	if (pci_clear_pcib) {
+		pci_write_config(dev, PCIR_IOBASEL_1, 0xff, 1);
+		pci_write_config(dev, PCIR_IOBASEH_1, 0xffff, 2);
+		pci_write_config(dev, PCIR_IOLIMITL_1, 0, 1);
+		pci_write_config(dev, PCIR_IOLIMITH_1, 0, 2);
+		pci_write_config(dev, PCIR_MEMBASE_1, 0xffff, 2);
+		pci_write_config(dev, PCIR_MEMLIMIT_1, 0, 2);
+		pci_write_config(dev, PCIR_PMBASEL_1, 0xffff, 2);
+		pci_write_config(dev, PCIR_PMBASEH_1, 0xffffffff, 4);
+		pci_write_config(dev, PCIR_PMLIMITL_1, 0, 2);
+		pci_write_config(dev, PCIR_PMLIMITH_1, 0, 4);
+	}
+
 	/* Determine if the I/O port window is implemented. */
 	val = pci_read_config(dev, PCIR_IOBASEL_1, 1);
 	if (val == 0) {