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>

1 files changed, 2 insertions, 2 deletions

diff --git a/util/sconfig/sconfig.y b/util/sconfig/sconfig.y
index 0d894a9e35..d55b18bda9 100755
--- a/util/sconfig/sconfig.y
+++ b/util/sconfig/sconfig.y
@@ -31,7 +31,7 @@ static struct chip_instance *cur_chip_instance;
 	int number;
 }
 
-%token CHIP DEVICE REGISTER BOOL HIDDEN BUS RESOURCE END EQUALS HEX STRING PCI PNP I2C APIC CPU_CLUSTER CPU DOMAIN IRQ DRQ SLOT_DESC IO NUMBER SUBSYSTEMID INHERIT IOAPIC_IRQ IOAPIC PCIINT GENERIC SPI USB MMIO
+%token CHIP DEVICE REGISTER BOOL STATUS MANDATORY BUS RESOURCE END EQUALS HEX STRING PCI PNP I2C APIC CPU_CLUSTER CPU DOMAIN IRQ DRQ SLOT_DESC IO NUMBER SUBSYSTEMID INHERIT IOAPIC_IRQ IOAPIC PCIINT GENERIC SPI USB MMIO
 %%
 devtree: { cur_parent = root_parent; } chip;
 
@@ -56,7 +56,7 @@ device: DEVICE BUS NUMBER /* == devnum */ status {
 	cur_parent = $<dev>5->parent;
 };
 
-status: BOOL | HIDDEN;
+status: BOOL | STATUS ;
 
 resource: RESOURCE NUMBER /* == resnum */ EQUALS NUMBER /* == resval */
 	{ add_resource(cur_parent, $<number>1, strtol($<string>2, NULL, 0), strtol($<string>4, NULL, 0)); } ;