Re: [PATCH v4 3/3] powerpc/powernv: Parse device tree, population of SPR support
From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2020-03-17 03:13:33
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Pratik Rajesh Sampat [off-list ref] writes:
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.
These should be documented in: Documentation/devicetree/bindings/powerpc/opal/power-mgt.txt
quoted hunk ↗ jump to hunk
diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c index 97aeb45e897b..27dfadf609e8 100644 --- a/arch/powerpc/platforms/powernv/idle.c +++ b/arch/powerpc/platforms/powernv/idle.c@@ -1436,6 +1436,85 @@ 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; + u64 bit_pos; + + nr_sprns = of_property_count_u64_elems(np, "sprn-bitmask"); + if (nr_sprns <= 0) + return rc;
Using <= 0 means zero SPRs is treated by success as the caller, is that intended? If so a comment would be appropriate.
+ 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;This is basically a hand coded bitmap, see eg. BIT_WORD(), BIT_MASK() etc. I don't think there's an easy way to convert temp_u64 into a proper bitmap, so it's probably not worth doing that. But at least use the macros.
+ 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 *sr_np, *ss_np;You never use these concurrently AFAICS, so you could just have a single *np.
+ int rc = 0, i;
+
+ /* Self restore register population */
+ sr_np = of_find_node_by_path("/ibm,opal/power-mgt/self-restore");I know the existing idle code uses of_find_node_by_path(), but that's because it's old and crufty. Please don't add new searches by path. You should be searching by compatible.
+ if (!sr_np) {
+ pr_warn("opal: self restore Node not found");This warning and the others below will fire on all existing firmware versions, which is not OK.
+ } else {
+ rc = extract_save_restore_state_dt(sr_np, SELF_RESTORE_TYPE);
+ if (rc != 0)
+ return rc;
+ }
+ /* Self save register population */
+ ss_np = of_find_node_by_path("/ibm,opal/power-mgt/self-save");
+ if (!ss_np) {
+ pr_warn("opal: self save Node not found");
+ pr_warn("Legacy firmware. Assuming default self-restore support");
+ for (i = 0; i < nr_preferred_sprs; i++)
+ preferred_sprs[i].supported_mode &= ~SELF_SAVE_STRICT;
+ } else {
+ rc = extract_save_restore_state_dt(ss_np, SELF_SAVE_TYPE);
+ }
+ return rc;You're leaking references on all the device_nodes in here, you need of_node_put() before exiting.
+}
cheers