[Skiboot] [PATCH v3 1/3] init, occ: Initialise OCC earlier on BMC systems

[Andrew Donnellan]

We need to use the OCC to obtain presence data for the SXM2 slots on
Witherspoon systems. This is needed to determine device type for NVLink
GPUs and OpenCAPI devices which can be plugged into the same slot. Support
for this will be implemented in a future patch.

Currently, OCC initialisation is done just before handing over to Linux,
which is well after NPU probe. On FSP systems, OCC boot starts very late,
so we wait until the last possible moment to initialise the skiboot side in
order to give it the maximum time to boot. On BMC systems, OCC boot starts
earlier, so there aren't any issues in moving it earlier in the skiboot
init sequence.

When running on a BMC machine, call occ_pstates_init() as early as
possible in the init sequence. On FSP machines, continue to call it from
its current location.

Signed-off-by: Andrew Donnellan <andrew.donnellan at au1.ibm.com>

---

v1->v2:

 - Change check to rely on BMC vs FSP rather than POWER8 vs POWER9 (thanks
   Shilpa)
---
 core/init.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/core/init.c b/core/init.c
index 1ad747e77e4a..272a57a145ee 100644
--- a/core/init.c
+++ b/core/init.c
@@ -505,7 +505,8 @@ void __noreturn load_and_boot_kernel(bool is_reboot)
 
 	ipmi_set_fw_progress_sensor(IPMI_FW_OS_BOOT);
 
-	occ_pstates_init();
+	if (fsp_present())
+		occ_pstates_init();
 
 	if (!is_reboot) {
 		/* We wait for the nvram read to complete here so we can
@@ -1079,6 +1080,17 @@ void __noreturn __nomcount main_cpu_entry(const void *fdt)
 
 	op_display(OP_LOG, OP_MOD_INIT, 0x0002);
 
+	/*
+	 * On some POWER9 BMC systems, we need to initialise the OCC
+	 * before the NPU to facilitate NVLink/OpenCAPI presence
+	 * detection, so we set it up as early as possible. On FSP
+	 * systems, Hostboot starts booting the OCC later, so we delay
+	 * OCC initialisation as late as possible to give it the
+	 * maximum time to boot up.
+	 */
+	if (!fsp_present())
+		occ_pstates_init();
+
 	pci_nvram_init();
 
 	preload_io_vpd();
-- 
git-series 0.9.1