sb/intel/lynxpoint: Handle H81 only having 6 PCIe root ports

The H81 chipset is the only non-LP Lynx Point chipset with 6 PCIe root
ports, all others have 8 [1]. The existing PCIe code assumed that all
non-LP chipsets had 8 root ports, which meant that port 6 would not be
considered the last root port on H81, so `root_port_commit_config()`
would not run. Ultimately, while PCIe still worked on H81, all the root
ports would remain enabled, even if disabled in the devicetree.

Also, remove `PCI_DEVICE_ID_INTEL_LYNXPOINT_MOB_DESK_{MIN,MAX}`, as they
are unused, and the MAX constant is incorrect.

Interestingly, this fixes an issue where GRUB is unable to halt the
system.

Tested on an ASRock H81M-HDS. The root ports disabled in the devicetree
do indeed end up disabled.

[1] Intel® 8 Series/C220 Series Chipset Family Platform Controller Hub
    (PCH) Datasheet, revision 003, document number 328904.

Change-Id: If3ce217e8a4f4ea4e111e4525b03dbbfc63f92b0
Signed-off-by: Tristan Corrick <tristan@corrick.kiwi>
Reviewed-on: https://review.coreboot.org/c/30077
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/src/southbridge/intel/lynxpoint/pch.c b/src/southbridge/intel/lynxpoint/pch.c
index 6596aa2f5d..1fb6d7ad54 100644
--- a/src/southbridge/intel/lynxpoint/pch.c
+++ b/src/southbridge/intel/lynxpoint/pch.c
@@ -45,6 +45,16 @@ int pch_silicon_revision(void)
 	return pch_revision_id;
 }
 
+int pch_silicon_id(void)
+{
+	static int pch_id = -1;
+
+	if (pch_id < 0)
+		pch_id = pci_read_config16(pch_get_lpc_device(), PCI_DEVICE_ID);
+
+	return pch_id;
+}
+
 int pch_silicon_type(void)
 {
 	static int pch_type = -1;