sb/intel/lynxpoint: Add PCH platform type function

Current code only cares whether the PCH is LP or not. However, MRC wants
to differentiate between desktop and non-LP mobile platforms as well. As
the PCH is soldered onto the mainboard, add a facility to retrieve which
platform coreboot is running on by checking the PCH's LPC device ID. The
only user of the `pch_silicon_type` function is the `pch_is_lp` function
so replace the former with the new `get_pch_platform_type` function. The
function needs to be defined in both romstage and ramstage where PCI ops
have different signatures, hence the two copies.

Change-Id: Ib6276e0069eaa069a365faf6ae02dd934307d36c
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/43123
Reviewed-by: Patrick Rudolph <siro@das-labor.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

1 files changed, 13 insertions, 7 deletions

diff --git a/src/southbridge/intel/lynxpoint/pch.c b/src/southbridge/intel/lynxpoint/pch.c
index e3c5bb2ef0..0a0e489d6f 100644
--- a/src/southbridge/intel/lynxpoint/pch.c
+++ b/src/southbridge/intel/lynxpoint/pch.c
@@ -40,19 +40,25 @@ int pch_silicon_id(void)
 	return pch_id;
 }
 
-int pch_silicon_type(void)
+enum pch_platform_type get_pch_platform_type(void)
 {
-	static int pch_type = -1;
+	const u16 did = pci_read_config16(pch_get_lpc_device(), PCI_DEVICE_ID);
 
-	if (pch_type < 0)
-		pch_type = pci_read_config8(pch_get_lpc_device(),
-					    PCI_DEVICE_ID + 1);
-	return pch_type;
+	/* Check if this is a LPT-LP or WPT-LP device ID */
+	if ((did & 0xff00) == 0x9c00)
+		return PCH_TYPE_ULT;
+
+	/* Non-LP laptop SKUs have an odd device ID (least significant bit is one) */
+	if (did & 1)
+		return PCH_TYPE_MOBILE;
+
+	/* Desktop and Server SKUs have an even device ID */
+	return PCH_TYPE_DESKTOP;
 }
 
 int pch_is_lp(void)
 {
-	return pch_silicon_type() == PCH_TYPE_LPT_LP;
+	return get_pch_platform_type() == PCH_TYPE_ULT;
 }
 
 u16 get_pmbase(void)