[RFC 3/3] powerpc/powernv: Parse device tree, population of SPR support

[Pratik Rajesh Sampat]

Parse the device tree for nodes self-save, self-restore and populate
support for the preferred SPRs based what was advertised by the device
tree.

Signed-off-by: Pratik Rajesh Sampat <psampat@xxxxxxxxxxxxx>
---
 arch/powerpc/platforms/powernv/idle.c | 104 ++++++++++++++++++++++++++
 1 file changed, 104 insertions(+)

diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c
index e33bb3fd88ac..b86d5da4561d 100644
--- a/arch/powerpc/platforms/powernv/idle.c
+++ b/arch/powerpc/platforms/powernv/idle.c
@@ -1427,6 +1427,107 @@ static void __init pnv_probe_idle_states(void)
 		supported_cpuidle_states |= pnv_idle_states[i].flags;
 }
 
+/*
+ * Extracts and populates the self save or restore capabilities
+ * passed from the device tree node
+ */
+static int extract_save_restore_state_dt(struct device_node *np, int type)
+{
+	int nr_sprns = 0, i, bitmask_index;
+	int rc = 0;
+	u64 *temp_u64;
+	const char *state_prop;
+	u64 bit_pos;
+
+	state_prop = of_get_property(np, "status", NULL);
+	if (!state_prop) {
+		pr_warn("opal: failed to find the active value for self save/restore node");
+		return -EINVAL;
+	}
+	if (strncmp(state_prop, "disabled", 8) == 0) {
+		/*
+		 * if the feature is not active, strip the preferred_sprs from
+		 * that capability.
+		 */
+		if (type == SELF_RESTORE_TYPE) {
+			for (i = 0; i < nr_preferred_sprs; i++) {
+				preferred_sprs[i].supported_mode &=
+					~SELF_RESTORE_STRICT;
+			}
+		} else {
+			for (i = 0; i < nr_preferred_sprs; i++) {
+				preferred_sprs[i].supported_mode &=
+					~SELF_SAVE_STRICT;
+			}
+		}
+		return 0;
+	}
+	nr_sprns = of_property_count_u64_elems(np, "sprn-bitmask");
+	if (nr_sprns <= 0)
+		return rc;
+	temp_u64 = kcalloc(nr_sprns, sizeof(u64), GFP_KERNEL);
+	if (of_property_read_u64_array(np, "sprn-bitmask",
+				       temp_u64, nr_sprns)) {
+		pr_warn("cpuidle-powernv: failed to find registers in DT\n");
+		kfree(temp_u64);
+		return -EINVAL;
+	}
+	/*
+	 * Populate acknowledgment of support for the sprs in the global vector
+	 * gotten by the registers supplied by the firmware.
+	 * The registers are in a bitmask, bit index within
+	 * that specifies the SPR
+	 */
+	for (i = 0; i < nr_preferred_sprs; i++) {
+		bitmask_index = preferred_sprs[i].spr / 64;
+		bit_pos = preferred_sprs[i].spr % 64;
+		if ((temp_u64[bitmask_index] & (1UL << bit_pos)) == 0) {
+			if (type == SELF_RESTORE_TYPE)
+				preferred_sprs[i].supported_mode &=
+					~SELF_RESTORE_STRICT;
+			else
+				preferred_sprs[i].supported_mode &=
+					~SELF_SAVE_STRICT;
+			continue;
+		}
+		if (type == SELF_RESTORE_TYPE) {
+			preferred_sprs[i].supported_mode |=
+				SELF_RESTORE_STRICT;
+		} else {
+			preferred_sprs[i].supported_mode |=
+				SELF_SAVE_STRICT;
+		}
+	}
+
+	kfree(temp_u64);
+	return rc;
+}
+
+static int pnv_parse_deepstate_dt(void)
+{
+	struct device_node *np, *np1;
+	int rc = 0;
+
+	/* Self restore register population */
+	np = of_find_node_by_path("/ibm,opal/power-mgt/self-restore");
+	if (!np) {
+		pr_warn("opal: self restore Node not found");
+	} else {
+		rc = extract_save_restore_state_dt(np, SELF_RESTORE_TYPE);
+		if (rc != 0)
+			return rc;
+	}
+	/* Self save register population */
+	np1 = of_find_node_by_path("/ibm,opal/power-mgt/self-save");
+	if (!np1) {
+		pr_warn("opal: self save Node not found");
+		pr_warn("Legacy firmware. Assuming default self-restore support");
+	} else {
+		rc = extract_save_restore_state_dt(np1, SELF_SAVE_TYPE);
+	}
+	return rc;
+}
+
 /*
  * This function parses device-tree and populates all the information
  * into pnv_idle_states structure. It also sets up nr_pnv_idle_states
@@ -1575,6 +1676,9 @@ static int __init pnv_init_idle_states(void)
 		return rc;
 	pnv_probe_idle_states();
 
+	rc = pnv_parse_deepstate_dt();
+	if (rc)
+		return rc;
 	if (!cpu_has_feature(CPU_FTR_ARCH_300)) {
 		if (!(supported_cpuidle_states & OPAL_PM_SLEEP_ENABLED_ER1)) {
 			power7_fastsleep_workaround_entry = false;
-- 
2.21.0