[M] Change in coreboot[master]: mb/google/myst: Enable PCIe devices in devicetree

[Karthik Ramasubramanian (Code Review)]

Attention is currently required from: Raul Rangel, Martin L Roth, Jon Murphy, Tim Van Patten, Felix Held.

Karthik Ramasubramanian has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/74112 )

Change subject: mb/google/myst: Enable PCIe devices in devicetree
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Patch Set 38: Code-Review+2

(1 comment)

File src/mainboard/google/myst/port_descriptors.c:

https://review.coreboot.org/c/coreboot/+/74112/comment/31e97fe6_b23b1156 
PS36, Line 44: 	{ /* SSD TODO(b/277815815): Enable PCIe GEN4 when supported */
> We do use the bridge, our option is BH799BB.  go/bayhub-reference. […]

A FW_config bit does not hurt to indicate whether it is a eMMC or NVME SKU. In Whiterun and Markarth, we used the state of CLK_REQ line to detect the SKU. Even though it is working now, I am also seeing some SSD devices not driving the CLK_REQ line to low as expected.

From that standpoint, FW_CONFIG bit will provide a deterministic way of identifying the storage type even if the storage device is not behaving as expected.