perf/arm-cmn: Streamline node iteration

Refactor the places where we scan through the set of nodes to switch
from explicit array indexing to pointer-based iteration. This leads to
slightly simpler object code, but also makes the source less dense and
more pleasant for further development. It also unearths an almost-bug
in arm_cmn_event_init() where we've been depending on the "array index"
of NULL relative to cmn->dns being a sufficiently large number, yuck.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/ee0c9eda9a643f46001ac43aadf3f0b1fd5660dd.1638530442.git.robin.murphy@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/drivers/perf/arm-cmn.c b/drivers/perf/arm-cmn.c
index adf50d6137345917a1b5c5f6d98c896be5629d5b..da7bf779fec2bd237b51694f6a68ce70374f5086 100644 (file)
--- a/drivers/perf/arm-cmn.c
+++ b/drivers/perf/arm-cmn.c
@@ -299,11 +299,11 @@ static struct arm_cmn_node *arm_cmn_node_to_xp(struct arm_cmn_node *dn)
 static struct arm_cmn_node *arm_cmn_node(const struct arm_cmn *cmn,
                                         enum cmn_node_type type)
 {
-       int i;
+       struct arm_cmn_node *dn;
 
-       for (i = 0; i < cmn->num_dns; i++)
-               if (cmn->dns[i].type == type)
-                       return &cmn->dns[i];
+       for (dn = cmn->dns; dn->type; dn++)
+               if (dn->type == type)
+                       return dn;
        return NULL;
 }
 
@@ -941,8 +941,8 @@ static int arm_cmn_event_init(struct perf_event *event)
 {
        struct arm_cmn *cmn = to_cmn(event->pmu);
        struct arm_cmn_hw_event *hw = to_cmn_hw(event);
+       struct arm_cmn_node *dn;
        enum cmn_node_type type;
-       unsigned int i;
        bool bynodeid;
        u16 nodeid, eventid;
 
@@ -974,10 +974,12 @@ static int arm_cmn_event_init(struct perf_event *event)
        nodeid = CMN_EVENT_NODEID(event);
 
        hw->dn = arm_cmn_node(cmn, type);
-       for (i = hw->dn - cmn->dns; i < cmn->num_dns && cmn->dns[i].type == type; i++) {
+       if (!hw->dn)
+               return -EINVAL;
+       for (dn = hw->dn; dn->type == type; dn++) {
                if (!bynodeid) {
                        hw->num_dns++;
-               } else if (cmn->dns[i].id != nodeid) {
+               } else if (dn->id != nodeid) {
                        hw->dn++;
                } else {
                        hw->num_dns = 1;
@@ -1332,7 +1334,7 @@ static int arm_cmn_init_dtcs(struct arm_cmn *cmn)
 
        cmn->xps = arm_cmn_node(cmn, CMN_TYPE_XP);
 
-       for (dn = cmn->dns; dn < cmn->dns + cmn->num_dns; dn++) {
+       for (dn = cmn->dns; dn->type; dn++) {
                if (dn->type != CMN_TYPE_XP)
                        arm_cmn_init_node_to_xp(cmn, dn);
                else if (cmn->num_dtcs == 1)
@@ -1382,6 +1384,7 @@ static int arm_cmn_discover(struct arm_cmn *cmn, unsigned int rgn_offset)
        u32 xp_offset[CMN_MAX_XPS];
        u64 reg;
        int i, j;
+       size_t sz;
 
        cfg_region = cmn->base + rgn_offset;
        reg = readl_relaxed(cfg_region + CMN_CFGM_PERIPH_ID_2);
@@ -1408,14 +1411,13 @@ static int arm_cmn_discover(struct arm_cmn *cmn, unsigned int rgn_offset)
                cmn->num_dns += FIELD_GET(CMN_CI_CHILD_COUNT, reg);
        }
 
-       /* Cheeky +1 to help terminate pointer-based iteration */
-       cmn->dns = devm_kcalloc(cmn->dev, cmn->num_dns + 1,
-                               sizeof(*cmn->dns), GFP_KERNEL);
-       if (!cmn->dns)
+       /* Cheeky +1 to help terminate pointer-based iteration later */
+       dn = devm_kcalloc(cmn->dev, cmn->num_dns + 1, sizeof(*dn), GFP_KERNEL);
+       if (!dn)
                return -ENOMEM;
 
        /* Pass 2: now we can actually populate the nodes */
-       dn = cmn->dns;
+       cmn->dns = dn;
        for (i = 0; i < cmn->num_xps; i++) {
                void __iomem *xp_region = cmn->base + xp_offset[i];
                struct arm_cmn_node *xp = dn++;
@@ -1484,6 +1486,11 @@ static int arm_cmn_discover(struct arm_cmn *cmn, unsigned int rgn_offset)
        /* Correct for any nodes we skipped */
        cmn->num_dns = dn - cmn->dns;
 
+       sz = (void *)(dn + 1) - (void *)cmn->dns;
+       dn = devm_krealloc(cmn->dev, cmn->dns, sz, GFP_KERNEL);
+       if (dn)
+               cmn->dns = dn;
+
        /*
         * If mesh_x wasn't set during discovery then we never saw
         * an XP at (0,1), thus we must have an Nx1 configuration.