[Skiboot] [PATCH] vas: Disable VAS/NX-842 on some P9 revisions

[Sukadev Bhattiprolu]

VAS/NX-842 are not functional on some P9 revisions, so disable them
in hardware and skip creating their device tree nodes.

Since the intent is to prevent OS from configuring VAS/NX, we remove
only the platform device nodes but leave the VAS/NX DT nodes under
xscom (i.e we don't skip add_vas_node() in hdata/spira.c)

Thanks to input from Michael Ellerman, Michael Neuling.

Signed-off-by: Sukadev Bhattiprolu <sukadev at linux.vnet.ibm.com>
---
 hw/nx.c       |  5 +++++
 hw/vas.c      | 47 ++++++++++++++++++++++++++++++++++++++++++++---
 include/vas.h |  1 +
 3 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/hw/nx.c b/hw/nx.c
index 0f6ff04..784a553 100644
--- a/hw/nx.c
+++ b/hw/nx.c
@@ -24,6 +24,7 @@
 #include <chip.h>
 #include <xscom-p9-regs.h>
 #include <phys-map.h>
+#include <vas.h>
 #include <p9_stop_api.H>
 
 static void p9_darn_init(void)
@@ -110,6 +111,10 @@ void nx_p9_rng_late_init(void)
 static void nx_init_one(struct dt_node *node)
 {
 	nx_create_rng_node(node);
+
+	if (vas_nx_disabled())
+		return;
+
 	nx_create_crypto_node(node);
 	nx_create_compress_node(node);
 }
diff --git a/hw/vas.c b/hw/vas.c
index fb5a1e7..6362f7e 100644
--- a/hw/vas.c
+++ b/hw/vas.c
@@ -69,6 +69,36 @@ static int vas_scom_write(struct proc_chip *chip, uint64_t reg, uint64_t val)
 	return rc;
 }
 
+/*
+ * VAS and hence, NX-842 are disabled in following POWER9 revisions:
+ *
+ *	- Nimbus DD1.X, DD2.01, DD2.1
+ *	- Cumulus DD1.0
+ *
+ * Return true for those revisions. Return false for others.
+ */
+__attrconst inline bool vas_nx_disabled(void)
+{
+	uint32_t pvr;
+	int major, minor;
+	struct proc_chip *chip;
+
+	chip = next_chip(NULL);
+
+	pvr = mfspr(SPR_PVR);
+	major = PVR_VERS_MAJ(pvr);
+	minor = PVR_VERS_MIN(pvr);
+
+	switch (chip->type) {
+	case PROC_CHIP_P9_NIMBUS:
+		return (major < 2 || (major == 2 && minor <= 1));
+	case PROC_CHIP_P9_CUMULUS:
+		return (major == 1 && minor == 0);
+	default:
+		return false;
+	}
+}
+
 /* Interface for NX - make sure VAS is fully initialized first */
 __attrconst inline uint64_t vas_get_hvwc_mmio_bar(const int chipid)
 {
@@ -110,6 +140,9 @@ static int init_north_ctl(struct proc_chip *chip)
 	return vas_scom_write(chip, VAS_MISC_N_CTL, val);
 }
 
+/*
+ * Ensure paste instructions are not accepted and MMIO BARs are disabled.
+ */
 static inline int reset_north_ctl(struct proc_chip *chip)
 {
 	return vas_scom_write(chip, VAS_MISC_N_CTL, 0ULL);
@@ -399,7 +432,7 @@ static void disable_vas_inst(struct dt_node *np)
 /*
  * Initialize one VAS instance
  */
-static int init_vas_inst(struct dt_node *np)
+static int init_vas_inst(struct dt_node *np, bool disabled)
 {
 	uint32_t vas_id;
 	uint64_t xscom_base;
@@ -411,6 +444,11 @@ static int init_vas_inst(struct dt_node *np)
 
 	chip->vas = alloc_vas(chip->id, vas_id, xscom_base);
 
+	if (disabled) {
+		reset_north_ctl(chip);
+		return 0;
+	}
+
 	if (alloc_init_wcbs(chip))
 		return -1;
 
@@ -429,17 +467,20 @@ static int init_vas_inst(struct dt_node *np)
 
 void vas_init()
 {
+	bool disabled;
 	struct dt_node *np;
 
 	if (proc_gen != proc_gen_p9)
 		return;
 
+	disabled = vas_nx_disabled();
+
 	dt_for_each_compatible(dt_root, np, "ibm,power9-vas-x") {
-		if (init_vas_inst(np))
+		if (init_vas_inst(np, disabled))
 			goto out;
 	}
 
-	vas_initialized = 1;
+	vas_initialized = !disabled;
 	return;
 
 out:
diff --git a/include/vas.h b/include/vas.h
index 6bc2a1c..2e37908 100644
--- a/include/vas.h
+++ b/include/vas.h
@@ -37,6 +37,7 @@
  */
 
 extern void vas_init(void);
+extern __attrconst bool vas_nx_disabled(void);
 extern __attrconst uint64_t vas_get_hvwc_mmio_bar(const int chipid);
 extern __attrconst uint64_t vas_get_wcbs_bar(int chipid);
 
-- 
2.7.4