gpu: nvgpu: add read_ptimer to gops

Move all places that read ptimer to use the callback.
It's for add vgpu implementation of read ptimer.

Bug 1395833

Change-Id: Ia339f2f08d75ca4969a443fffc9a61cff1d3d2b7
Signed-off-by: Richard Zhao <rizhao@nvidia.com>
Reviewed-on: http://git-master/r/1159587
(cherry picked from commit a01f804684f875c9cffc31eb2c1038f2f29ec66f)
Reviewed-on: http://git-master/r/1158449
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>
Tested-by: Terje Bergstrom <tbergstrom@nvidia.com>

1 files changed, 36 insertions, 9 deletions

diff --git a/drivers/gpu/nvgpu/gk20a/gk20a.c b/drivers/gpu/nvgpu/gk20a/gk20a.c
index d21d0527..db77d40f 100644
--- a/drivers/gpu/nvgpu/gk20a/gk20a.c
+++ b/drivers/gpu/nvgpu/gk20a/gk20a.c
@@ -2227,18 +2227,45 @@ gk20a_request_firmware(struct gk20a *g, const char *fw_name)
         return fw;
 }
 
-
-u64 gk20a_read_ptimer(struct gk20a *g)
+int gk20a_read_ptimer(struct gk20a *g, u64 *value)
 {
-        u32 time_hi0 = gk20a_readl(g, timer_time_1_r());
-        u32 time_lo = gk20a_readl(g, timer_time_0_r());
-        u32 time_hi1 = gk20a_readl(g, timer_time_1_r());
-        u32 time_hi = (time_lo & (1L << 31)) ? time_hi0 : time_hi1;
-        u64 time = ((u64)time_hi << 32) | time_lo;
+        const unsigned int max_iterations = 3;
+        unsigned int i = 0;
+        u32 gpu_timestamp_hi_prev = 0;
 
-        return time;
-}
+        if (!value)
+                return -EINVAL;
+
+        /* Note. The GPU nanosecond timer consists of two 32-bit
+         * registers (high & low). To detect a possible low register
+         * wrap-around between the reads, we need to read the high
+         * register before and after low. The wraparound happens
+         * approximately once per 4 secs. */
+
+        /* get initial gpu_timestamp_hi value */
+        gpu_timestamp_hi_prev = gk20a_readl(g, timer_time_1_r());
+
+        for (i = 0; i < max_iterations; ++i) {
+                u32 gpu_timestamp_hi = 0;
+                u32 gpu_timestamp_lo = 0;
+
+                gpu_timestamp_lo = gk20a_readl(g, timer_time_0_r());
+                gpu_timestamp_hi = gk20a_readl(g, timer_time_1_r());
 
+                if (gpu_timestamp_hi == gpu_timestamp_hi_prev) {
+                        *value = (((u64)gpu_timestamp_hi) << 32) |
+                                gpu_timestamp_lo;
+                        return 0;
+                }
+
+                /* wrap-around detected, retry */
+                gpu_timestamp_hi_prev = gpu_timestamp_hi;
+        }
+
+        /* too many iterations, bail out */
+        gk20a_err(dev_from_gk20a(g), "failed to read ptimer");
+        return -EBUSY;
+}
 
 MODULE_LICENSE("GPL v2");
 module_init(gk20a_init);