Add configurable ramstage support for minimal PCI scanning
This CL has changes that allow us to enable a configurable
ramstage, and one change that allows us to minimize PCI
scanning. Minimal scanning is a frequently requested feature.
To enable it, we add two new variables to src/Kconfig
CONFIGURABLE_RAMSTAGE
is the overall variable controlling other options for minimizing the
ramstage.
MINIMAL_PCI_SCANNING is how we indicate we wish to enable minimal
PCI scanning.
Some devices must be scanned in all cases, such as 0:0.0.
To indicate which devices we must scan, we add a new mandatory
keyword to sconfig
It is used in place of on, off, or hidden, and indicates
a device is enabled and mandatory. Mandatory
devices are always scanned. When MINIMAL_PCI_SCANNING is enabled,
ONLY mandatory devices are scanned.
We further add support in src/device/pci_device.c to manage
both MINIMAL_PCI_SCANNING and mandatory devices.
Finally, to show how this works in practice, we add mandatory
keywords to 3 devices on the qemu-q35.
TEST=
1. This is tested and working on the qemu-q35 target.
2. On CML-Hatch
Before CL:
Total Boot time: ~685ms
After CL:
Total Boot time: ~615ms
Change-Id: I2073d9f8e9297c2b02530821ebb634ea2a5c758e
Signed-off-by: Ronald G. Minnich <rminnich@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/36221
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Jeremy Soller <jeremy@system76.com>
diff --git a/src/device/pci_device.c b/src/device/pci_device.c
index 47c0e9f..b1e88a6 100644
--- a/src/device/pci_device.c
+++ b/src/device/pci_device.c
@@ -1195,6 +1195,12 @@
* non-existence and single function devices.
*/
for (devfn = min_devfn; devfn <= max_devfn; devfn++) {
+ if (CONFIG(MINIMAL_PCI_SCANNING)) {
+ dev = pcidev_path_behind(bus, devfn);
+ if (!dev || !dev->mandatory)
+ continue;
+ }
+
/* First thing setup the device structure. */
dev = pci_scan_get_dev(bus, devfn);