[PATCH 31/48] staging: etnaviv: improve efficiency of command parser

[Lucas Stach]

From: Russell King <rmk+ker...@arm.linux.org.uk>

Performance analysis indicates that the command parser is a hot spot
in the code.  We can improve the efficiency of the command parser by
storing the command length in a table, rather than decoding the
command manually via a switch statement.

Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
---
 drivers/staging/etnaviv/etnaviv_cmd_parser.c | 34 +++++++++++++---------------
 1 file changed, 16 insertions(+), 18 deletions(-)

diff --git a/drivers/staging/etnaviv/etnaviv_cmd_parser.c 
b/drivers/staging/etnaviv/etnaviv_cmd_parser.c
index d866b8e2381d..7ae6ddb4306e 100644
--- a/drivers/staging/etnaviv/etnaviv_cmd_parser.c
+++ b/drivers/staging/etnaviv/etnaviv_cmd_parser.c
@@ -54,6 +54,13 @@ static bool etnaviv_validate_load_state(struct etnaviv_gpu 
*gpu, u32 *buf,
        return true;
 }

+static uint8_t cmd_length[32] = {
+       [FE_OPCODE_DRAW_PRIMITIVES] = 4,
+       [FE_OPCODE_DRAW_INDEXED_PRIMITIVES] = 6,
+       [FE_OPCODE_NOP] = 2,
+       [FE_OPCODE_STALL] = 2,
+};
+
 bool etnaviv_cmd_validate_one(struct etnaviv_gpu *gpu,
        struct etnaviv_gem_object *obj, unsigned int offset, unsigned int size)
 {
@@ -69,7 +76,7 @@ bool etnaviv_cmd_validate_one(struct etnaviv_gpu *gpu,
                switch (op) {
                case FE_OPCODE_LOAD_STATE:
                        n = EXTRACT(cmd, VIV_FE_LOAD_STATE_HEADER_COUNT);
-                       len = 1 + n;
+                       len = ALIGN(1 + n, 2);
                        if (buf + len > end)
                                break;

@@ -89,26 +96,17 @@ bool etnaviv_cmd_validate_one(struct etnaviv_gpu *gpu,
                        len = 2 + n * 2;
                        break;

-               case FE_OPCODE_DRAW_PRIMITIVES:
-                       len = 4;
-                       break;
-
-               case FE_OPCODE_DRAW_INDEXED_PRIMITIVES:
-                       len = 6;
-                       break;
-
-               case FE_OPCODE_NOP:
-               case FE_OPCODE_STALL:
-                       len = 2;
-                       break;
-
                default:
-                       dev_err(gpu->dev, "%s: op %u not permitted at offset 
%tu\n",
-                               __func__, op, buf - start);
-                       return false;
+                       len = cmd_length[op];
+                       if (len == 0) {
+                               dev_err(gpu->dev, "%s: op %u not permitted at 
offset %tu\n",
+                                       __func__, op, buf - start);
+                               return false;
+                       }
+                       break;
                }

-               buf += ALIGN(len, 2);
+               buf += len;
        }

        if (buf > end) {
-- 
2.5.1