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Add configurable ramstage support for minimal PCI scanning

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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>
This commit is contained in:
Ronald G. Minnich
2019-10-22 02:02:24 +00:00
committed by ron minnich
parent 91dc1e74a5
commit 466ca2c1ad
11 changed files with 387 additions and 355 deletions
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15
src/Kconfig
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@@ -354,6 +354,21 @@ config RAMPAYLOAD
Skip PCI enumeration logic and only allocate BAR for fixed devices
(bootable devices, TPM over GSPI).
config CONFIGURABLE_RAMSTAGE
bool "Enable a configurable ramstage."
default y if ARCH_X86
help
A configurable ramstage allows you to select which parts of the ramstage
to run. Currently, we can only select a minimal PCI scanning step.
The minimal PCI scanning will only check those parts that are enabled
in the devicetree.cb. By convention none of those devices should be bridges.
config MINIMAL_PCI_SCANNING
bool "Enable minimal PCI scanning"
depends on CONFIGURABLE_RAMSTAGE
help
If this option is enabled, coreboot will scan only devices
marked as mandatory in devicetree.cb
endmenu
menu "Mainboard"