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>
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ron minnich
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@@ -104,6 +104,8 @@ struct device {
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/* Indicates device status (enabled / hidden or not). */
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int enabled;
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int hidden;
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/* non-zero if the device should be included in all cases */
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int mandatory;
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/* Subsystem IDs for the device. */
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int subsystem_vendor;
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