GRU Driver V3: fixes to resolve code review comments

Fixes problems identified in a code review:
	- add comment with high level dscription of the GRU
	- prepend "gru_" to all global names
	- delete unused function
	- couple of trivial bug fixes

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Jack Steiner <steiner@sgi.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

7 files changed, 93 insertions, 29 deletions

diff --git a/drivers/misc/sgi-gru/gru_instructions.h b/drivers/misc/sgi-gru/gru_instructions.h
index 3159b261c5a7..0dc36225c7c6 100644
--- a/drivers/misc/sgi-gru/gru_instructions.h
+++ b/drivers/misc/sgi-gru/gru_instructions.h
@@ -285,16 +285,6 @@ __opword(unsigned char opcode, unsigned char exopc, unsigned char xtype,
 }
 
 /*
- * Prefetch a cacheline. Fetch is unconditional. Must page fault if
- * no valid TLB entry is found.
- *      ??? should I use actual "load" or hardware prefetch???
- */
-static inline void gru_prefetch(void *p)
-{
-        *(volatile char *)p;
-}
-
-/*
  * Architecture specific intrinsics
  */
 static inline void gru_flush_cache(void *p)
diff --git a/drivers/misc/sgi-gru/grufile.c b/drivers/misc/sgi-gru/grufile.c
index 09c9c65ff9d1..23c91f5f6b61 100644
--- a/drivers/misc/sgi-gru/grufile.c
+++ b/drivers/misc/sgi-gru/grufile.c
@@ -112,6 +112,10 @@ static int gru_file_mmap(struct file *file, struct vm_area_struct *vma)
         if ((vma->vm_flags & (VM_SHARED | VM_WRITE)) != (VM_SHARED | VM_WRITE))
                 return -EPERM;
 
+        if (vma->vm_start & (GRU_GSEG_PAGESIZE - 1) ||
+                        vma->vm_end & (GRU_GSEG_PAGESIZE - 1))
+                return -EINVAL;
+
         vma->vm_flags |=
             (VM_IO | VM_DONTCOPY | VM_LOCKED | VM_DONTEXPAND | VM_PFNMAP |
                         VM_RESERVED);
@@ -471,8 +475,8 @@ struct vm_operations_struct gru_vm_ops = {
 module_init(gru_init);
 module_exit(gru_exit);
 
-module_param(options, ulong, 0644);
-MODULE_PARM_DESC(options, "Various debug options");
+module_param(gru_options, ulong, 0644);
+MODULE_PARM_DESC(gru_options, "Various debug options");
 
 MODULE_AUTHOR("Silicon Graphics, Inc.");
 MODULE_LICENSE("GPL");
diff --git a/drivers/misc/sgi-gru/grukservices.c b/drivers/misc/sgi-gru/grukservices.c
index 234d165fb11e..dfd49af0fe18 100644
--- a/drivers/misc/sgi-gru/grukservices.c
+++ b/drivers/misc/sgi-gru/grukservices.c
@@ -638,11 +638,11 @@ int gru_kservices_init(struct gru_state *gru)
         cpus_possible = uv_blade_nr_possible_cpus(gru->gs_blade_id);
 
         num = GRU_NUM_KERNEL_CBR * cpus_possible;
-        cbr_map = reserve_gru_cb_resources(gru, GRU_CB_COUNT_TO_AU(num), NULL);
+        cbr_map = gru_reserve_cb_resources(gru, GRU_CB_COUNT_TO_AU(num), NULL);
         gru->gs_reserved_cbrs += num;
 
         num = GRU_NUM_KERNEL_DSR_BYTES * cpus_possible;
-        dsr_map = reserve_gru_ds_resources(gru, GRU_DS_BYTES_TO_AU(num), NULL);
+        dsr_map = gru_reserve_ds_resources(gru, GRU_DS_BYTES_TO_AU(num), NULL);
         gru->gs_reserved_dsr_bytes += num;
 
         gru->gs_active_contexts++;
@@ -673,7 +673,7 @@ int gru_kservices_init(struct gru_state *gru)
         }
         unlock_cch_handle(cch);
 
-        if (options & GRU_QUICKLOOK)
+        if (gru_options & GRU_QUICKLOOK)
                 quicktest(gru);
         return 0;
 }
diff --git a/drivers/misc/sgi-gru/grumain.c b/drivers/misc/sgi-gru/grumain.c
index aef6822cb80e..0eeb8dddd2f5 100644
--- a/drivers/misc/sgi-gru/grumain.c
+++ b/drivers/misc/sgi-gru/grumain.c
@@ -22,7 +22,7 @@
 #include "grutables.h"
 #include "gruhandles.h"
 
-unsigned long options __read_mostly;
+unsigned long gru_options __read_mostly;
 
 static struct device_driver gru_driver = {
         .name = "gru"
@@ -163,14 +163,14 @@ static unsigned long reserve_resources(unsigned long *p, int n, int mmax,
         return bits;
 }
 
-unsigned long reserve_gru_cb_resources(struct gru_state *gru, int cbr_au_count,
+unsigned long gru_reserve_cb_resources(struct gru_state *gru, int cbr_au_count,
                                        char *cbmap)
 {
         return reserve_resources(&gru->gs_cbr_map, cbr_au_count, GRU_CBR_AU,
                                  cbmap);
 }
 
-unsigned long reserve_gru_ds_resources(struct gru_state *gru, int dsr_au_count,
+unsigned long gru_reserve_ds_resources(struct gru_state *gru, int dsr_au_count,
                                        char *dsmap)
 {
         return reserve_resources(&gru->gs_dsr_map, dsr_au_count, GRU_DSR_AU,
@@ -182,10 +182,10 @@ static void reserve_gru_resources(struct gru_state *gru,
 {
         gru->gs_active_contexts++;
         gts->ts_cbr_map =
-            reserve_gru_cb_resources(gru, gts->ts_cbr_au_count,
+            gru_reserve_cb_resources(gru, gts->ts_cbr_au_count,
                                      gts->ts_cbr_idx);
         gts->ts_dsr_map =
-            reserve_gru_ds_resources(gru, gts->ts_dsr_au_count, NULL);
+            gru_reserve_ds_resources(gru, gts->ts_dsr_au_count, NULL);
 }
 
 static void free_gru_resources(struct gru_state *gru,
@@ -416,6 +416,7 @@ static void gru_free_gru_context(struct gru_thread_state *gts)
 
 /*
  * Prefetching cachelines help hardware performance.
+ * (Strictly a performance enhancement. Not functionally required).
  */
 static void prefetch_data(void *p, int num, int stride)
 {
@@ -746,6 +747,8 @@ again:
  * gru_nopage
  *
  * Map the user's GRU segment
+ *
+ *      Note: gru segments alway mmaped on GRU_GSEG_PAGESIZE boundaries.
  */
 int gru_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
@@ -757,6 +760,7 @@ int gru_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
                 vma, vaddr, GSEG_BASE(vaddr));
         STAT(nopfn);
 
+        /* The following check ensures vaddr is a valid address in the VMA */
         gts = gru_find_thread_state(vma, TSID(vaddr, vma));
         if (!gts)
                 return VM_FAULT_SIGBUS;
@@ -775,7 +779,7 @@ again:
         }
 
         if (!gts->ts_gru) {
-                while (!gru_assign_gru_context(gts)) {
+                if (!gru_assign_gru_context(gts)) {
                         mutex_unlock(&gts->ts_ctxlock);
                         preempt_enable();
                         schedule_timeout(GRU_ASSIGN_DELAY);  /* true hack ZZZ */
diff --git a/drivers/misc/sgi-gru/gruprocfs.c b/drivers/misc/sgi-gru/gruprocfs.c
index bdb1ad83bbfb..533923f83f1a 100644
--- a/drivers/misc/sgi-gru/gruprocfs.c
+++ b/drivers/misc/sgi-gru/gruprocfs.c
@@ -122,7 +122,7 @@ static ssize_t statistics_write(struct file *file, const char __user *userbuf,
 
 static int options_show(struct seq_file *s, void *p)
 {
-        seq_printf(s, "0x%lx\n", options);
+        seq_printf(s, "0x%lx\n", gru_options);
         return 0;
 }
 
@@ -136,7 +136,7 @@ static ssize_t options_write(struct file *file, const char __user *userbuf,
             (buf, userbuf, count < sizeof(buf) ? count : sizeof(buf)))
                 return -EFAULT;
         if (!strict_strtoul(buf, 10, &val))
-                options = val;
+                gru_options = val;
 
         return count;
 }
diff --git a/drivers/misc/sgi-gru/grutables.h b/drivers/misc/sgi-gru/grutables.h
index f97d84640129..4251018f70ff 100644
--- a/drivers/misc/sgi-gru/grutables.h
+++ b/drivers/misc/sgi-gru/grutables.h
@@ -24,6 +24,70 @@
 #define __GRUTABLES_H__
 
 /*
+ * GRU Chiplet:
+ *   The GRU is a user addressible memory accelerator. It provides
+ *   several forms of load, store, memset, bcopy instructions. In addition, it
+ *   contains special instructions for AMOs, sending messages to message
+ *   queues, etc.
+ *
+ *   The GRU is an integral part of the node controller. It connects
+ *   directly to the cpu socket. In its current implementation, there are 2
+ *   GRU chiplets in the node controller on each blade (~node).
+ *
+ *   The entire GRU memory space is fully coherent and cacheable by the cpus.
+ *
+ *   Each GRU chiplet has a physical memory map that looks like the following:
+ *
+ *      +-----------------+
+ *      |/////////////////|
+ *      |/////////////////|
+ *      |/////////////////|
+ *      |/////////////////|
+ *      |/////////////////|
+ *      |/////////////////|
+ *      |/////////////////|
+ *      |/////////////////|
+ *      +-----------------+
+ *      |  system control |
+ *      +-----------------+        _______ +-------------+
+ *      |/////////////////|       /        |             |
+ *      |/////////////////|      /         |             |
+ *      |/////////////////|     /          | instructions|
+ *      |/////////////////|    /           |             |
+ *      |/////////////////|   /            |             |
+ *      |/////////////////|  /             |-------------|
+ *      |/////////////////| /              |             |
+ *      +-----------------+                |             |
+ *      |   context 15    |                |  data       |
+ *      +-----------------+                |             |
+ *      |    ......       | \              |             |
+ *      +-----------------+  \____________ +-------------+
+ *      |   context 1     |
+ *      +-----------------+
+ *      |   context 0     |
+ *      +-----------------+
+ *
+ *   Each of the "contexts" is a chunk of memory that can be mmaped into user
+ *   space. The context consists of 2 parts:
+ *
+ *      - an instruction space that can be directly accessed by the user
+ *        to issue GRU instructions and to check instruction status.
+ *
+ *      - a data area that acts as normal RAM.
+ *
+ *   User instructions contain virtual addresses of data to be accessed by the
+ *   GRU. The GRU contains a TLB that is used to convert these user virtual
+ *   addresses to physical addresses.
+ *
+ *   The "system control" area of the GRU chiplet is used by the kernel driver
+ *   to manage user contexts and to perform functions such as TLB dropin and
+ *   purging.
+ *
+ *   One context may be reserved for the kernel and used for cross-partition
+ *   communication. The GRU will also be used to asynchronously zero out
+ *   large blocks of memory (not currently implemented).
+ *
+ *
  * Tables:
  *
  *      VDATA-VMA Data          - Holds a few parameters. Head of linked list of
@@ -190,14 +254,14 @@ struct gru_stats_s {
 #define GRU_STEAL_DELAY         ((HZ * 200) / 1000)
 
 #define STAT(id)        do {                                            \
-                                if (options & OPT_STATS)                \
+                                if (gru_options & OPT_STATS)            \
                                         atomic_long_inc(&gru_stats.id); \
                         } while (0)
 
 #ifdef CONFIG_SGI_GRU_DEBUG
 #define gru_dbg(dev, fmt, x...)                                         \
         do {                                                            \
-                if (options & OPT_DPRINT)                               \
+                if (gru_options & OPT_DPRINT)                           \
                         dev_dbg(dev, "%s: " fmt, __func__, x);          \
         } while (0)
 #else
@@ -529,9 +593,9 @@ extern void gru_flush_all_tlb(struct gru_state *gru);
 extern int gru_proc_init(void);
 extern void gru_proc_exit(void);
 
-extern unsigned long reserve_gru_cb_resources(struct gru_state *gru,
+extern unsigned long gru_reserve_cb_resources(struct gru_state *gru,
                 int cbr_au_count, char *cbmap);
-extern unsigned long reserve_gru_ds_resources(struct gru_state *gru,
+extern unsigned long gru_reserve_ds_resources(struct gru_state *gru,
                 int dsr_au_count, char *dsmap);
 extern int gru_fault(struct vm_area_struct *, struct vm_fault *vmf);
 extern struct gru_mm_struct *gru_register_mmu_notifier(void);
@@ -540,6 +604,6 @@ extern void gru_drop_mmu_notifier(struct gru_mm_struct *gms);
 extern void gru_flush_tlb_range(struct gru_mm_struct *gms, unsigned long start,
                                         unsigned long len);
 
-extern unsigned long options;
+extern unsigned long gru_options;
 
 #endif /* __GRUTABLES_H__ */
diff --git a/drivers/misc/sgi-gru/grutlbpurge.c b/drivers/misc/sgi-gru/grutlbpurge.c
index bb6b0e64e101..bcfd5425e2e6 100644
--- a/drivers/misc/sgi-gru/grutlbpurge.c
+++ b/drivers/misc/sgi-gru/grutlbpurge.c
@@ -242,7 +242,9 @@ static void gru_invalidate_range_end(struct mmu_notifier *mn,
         struct gru_mm_struct *gms = container_of(mn, struct gru_mm_struct,
                                                  ms_notifier);
 
-        atomic_dec(&gms->ms_range_active);
+        /* ..._and_test() provides needed barrier */
+        (void)atomic_dec_and_test(&gms->ms_range_active);
+
         wake_up_all(&gms->ms_wait_queue);
         gru_dbg(grudev, "gms %p, start 0x%lx, end 0x%lx\n", gms, start, end);
 }