IB/qib: Eliminate divide/mod in converting idx to egr buf pointer

The context init now saves a shift from rcvegrbufs_perchunk
rcvegrbufs_perchunk_shift using ilog2.   A BUG_ON() protects the
power of 2 assumption.

Signed-off-by: Mike Marciniszyn <mike.marciniszyn@qlogic.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

6 files changed, 18 insertions, 5 deletions

diff --git a/drivers/infiniband/hw/qib/qib.h b/drivers/infiniband/hw/qib/qib.h
index ee993e725d38..97e623383e1a 100644
--- a/drivers/infiniband/hw/qib/qib.h
+++ b/drivers/infiniband/hw/qib/qib.h
@@ -171,7 +171,9 @@ struct qib_ctxtdata {
         /* how many alloc_pages() chunks in rcvegrbuf_pages */
         u32 rcvegrbuf_chunks;
         /* how many egrbufs per chunk */
-        u32 rcvegrbufs_perchunk;
+        u16 rcvegrbufs_perchunk;
+        /* ilog2 of above */
+        u16 rcvegrbufs_perchunk_shift;
         /* order for rcvegrbuf_pages */
         size_t rcvegrbuf_size;
         /* rcvhdrq size (for freeing) */
@@ -940,7 +942,9 @@ struct qib_devdata {
         /* chip address space used by 4k pio buffers */
         u32 align4k;
         /* size of each rcvegrbuffer */
-        u32 rcvegrbufsize;
+        u16 rcvegrbufsize;
+        /* log2 of above */
+        u16 rcvegrbufsize_shift;
         /* localbus width (1, 2,4,8,16,32) from config space  */
         u32 lbus_width;
         /* localbus speed in MHz */
diff --git a/drivers/infiniband/hw/qib/qib_driver.c b/drivers/infiniband/hw/qib/qib_driver.c
index 23e584f4c36c..89264ffc7ee9 100644
--- a/drivers/infiniband/hw/qib/qib_driver.c
+++ b/drivers/infiniband/hw/qib/qib_driver.c
@@ -279,10 +279,10 @@ bail:
  */
 static inline void *qib_get_egrbuf(const struct qib_ctxtdata *rcd, u32 etail)
 {
-        const u32 chunk = etail / rcd->rcvegrbufs_perchunk;
-        const u32 idx =  etail % rcd->rcvegrbufs_perchunk;
+        const u32 chunk = etail >> rcd->rcvegrbufs_perchunk_shift;
+        const u32 idx =  etail & ((u32)rcd->rcvegrbufs_perchunk - 1);
 
-        return rcd->rcvegrbuf[chunk] + idx * rcd->dd->rcvegrbufsize;
+        return rcd->rcvegrbuf[chunk] + (idx << rcd->dd->rcvegrbufsize_shift);
 }
 
 /*
diff --git a/drivers/infiniband/hw/qib/qib_iba6120.c b/drivers/infiniband/hw/qib/qib_iba6120.c
index d8ca0a0b970d..781a802a321f 100644
--- a/drivers/infiniband/hw/qib/qib_iba6120.c
+++ b/drivers/infiniband/hw/qib/qib_iba6120.c
@@ -3273,6 +3273,8 @@ static int init_6120_variables(struct qib_devdata *dd)
         /* we always allocate at least 2048 bytes for eager buffers */
         ret = ib_mtu_enum_to_int(qib_ibmtu);
         dd->rcvegrbufsize = ret != -1 ? max(ret, 2048) : QIB_DEFAULT_MTU;
+        BUG_ON(!is_power_of_2(dd->rcvegrbufsize));
+        dd->rcvegrbufsize_shift = ilog2(dd->rcvegrbufsize);
 
         qib_6120_tidtemplate(dd);
 
diff --git a/drivers/infiniband/hw/qib/qib_iba7220.c b/drivers/infiniband/hw/qib/qib_iba7220.c
index e1f947446c2a..3f1d562ba898 100644
--- a/drivers/infiniband/hw/qib/qib_iba7220.c
+++ b/drivers/infiniband/hw/qib/qib_iba7220.c
@@ -4085,6 +4085,8 @@ static int qib_init_7220_variables(struct qib_devdata *dd)
         /* we always allocate at least 2048 bytes for eager buffers */
         ret = ib_mtu_enum_to_int(qib_ibmtu);
         dd->rcvegrbufsize = ret != -1 ? max(ret, 2048) : QIB_DEFAULT_MTU;
+        BUG_ON(!is_power_of_2(dd->rcvegrbufsize));
+        dd->rcvegrbufsize_shift = ilog2(dd->rcvegrbufsize);
 
         qib_7220_tidtemplate(dd);
 
diff --git a/drivers/infiniband/hw/qib/qib_iba7322.c b/drivers/infiniband/hw/qib/qib_iba7322.c
index 5ea9ece23b33..f3f4b55262c2 100644
--- a/drivers/infiniband/hw/qib/qib_iba7322.c
+++ b/drivers/infiniband/hw/qib/qib_iba7322.c
@@ -6205,6 +6205,8 @@ static int qib_init_7322_variables(struct qib_devdata *dd)
 
         /* we always allocate at least 2048 bytes for eager buffers */
         dd->rcvegrbufsize = max(mtu, 2048);
+        BUG_ON(!is_power_of_2(dd->rcvegrbufsize));
+        dd->rcvegrbufsize_shift = ilog2(dd->rcvegrbufsize);
 
         qib_7322_tidtemplate(dd);
 
diff --git a/drivers/infiniband/hw/qib/qib_init.c b/drivers/infiniband/hw/qib/qib_init.c
index 021636dbeae6..21ffa7c0915f 100644
--- a/drivers/infiniband/hw/qib/qib_init.c
+++ b/drivers/infiniband/hw/qib/qib_init.c
@@ -183,6 +183,9 @@ struct qib_ctxtdata *qib_create_ctxtdata(struct qib_pportdata *ppd, u32 ctxt)
                 rcd->rcvegrbuf_chunks = (rcd->rcvegrcnt +
                         rcd->rcvegrbufs_perchunk - 1) /
                         rcd->rcvegrbufs_perchunk;
+                BUG_ON(!is_power_of_2(rcd->rcvegrbufs_perchunk));
+                rcd->rcvegrbufs_perchunk_shift =
+                        ilog2(rcd->rcvegrbufs_perchunk);
         }
         return rcd;
 }