sch: make htb_rate_cfg and functions around that generic

As it is going to be used in tbf as well, push these to generic code.

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 37 insertions, 0 deletions

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 5d81a4478514..ffad48109a22 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -25,6 +25,7 @@
 #include <linux/rcupdate.h>
 #include <linux/list.h>
 #include <linux/slab.h>
+#include <net/sch_generic.h>
 #include <net/pkt_sched.h>
 #include <net/dst.h>
 
@@ -896,3 +897,39 @@ void dev_shutdown(struct net_device *dev)
 
         WARN_ON(timer_pending(&dev->watchdog_timer));
 }
+
+void psched_ratecfg_precompute(struct psched_ratecfg *r, u32 rate)
+{
+        u64 factor;
+        u64 mult;
+        int shift;
+
+        r->rate_bps = rate << 3;
+        r->shift = 0;
+        r->mult = 1;
+        /*
+         * Calibrate mult, shift so that token counting is accurate
+         * for smallest packet size (64 bytes).  Token (time in ns) is
+         * computed as (bytes * 8) * NSEC_PER_SEC / rate_bps.  It will
+         * work as long as the smallest packet transfer time can be
+         * accurately represented in nanosec.
+         */
+        if (r->rate_bps > 0) {
+                /*
+                 * Higher shift gives better accuracy.  Find the largest
+                 * shift such that mult fits in 32 bits.
+                 */
+                for (shift = 0; shift < 16; shift++) {
+                        r->shift = shift;
+                        factor = 8LLU * NSEC_PER_SEC * (1 << r->shift);
+                        mult = div64_u64(factor, r->rate_bps);
+                        if (mult > UINT_MAX)
+                                break;
+                }
+
+                r->shift = shift - 1;
+                factor = 8LLU * NSEC_PER_SEC * (1 << r->shift);
+                r->mult = div64_u64(factor, r->rate_bps);
+        }
+}
+EXPORT_SYMBOL(psched_ratecfg_precompute);