[PATCH v2 07/12] drm/amdgpu: read CPER ring via debugfs

[Xiang Liu]

From: Tao Zhou <tao.zh...@amd.com>

We read CPER data from read pointer to write pointer without changing
the pointers.

Signed-off-by: Tao Zhou <tao.zh...@amd.com>
Reviewed-by: Hawking Zhang <hawking.zh...@amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c | 47 ++++++++++++++++++------
 1 file changed, 36 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
index 005cdaee9987..510fe1ad0628 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
@@ -500,6 +500,7 @@ static ssize_t amdgpu_debugfs_ring_read(struct file *f, 
char __user *buf,
 {
        struct amdgpu_ring *ring = file_inode(f)->i_private;
        uint32_t value, result, early[3];
+       uint64_t p;
        loff_t i;
        int r;
 
@@ -523,18 +524,42 @@ static ssize_t amdgpu_debugfs_ring_read(struct file *f, 
char __user *buf,
                }
        }
 
-       while (size) {
-               if (*pos >= (ring->ring_size + 12))
-                       return result;
+       if (ring->funcs->type != AMDGPU_RING_TYPE_CPER) {
+               while (size) {
+                       if (*pos >= (ring->ring_size + 12))
+                               return result;
 
-               value = ring->ring[(*pos - 12)/4];
-               r = put_user(value, (uint32_t *)buf);
-               if (r)
-                       return r;
-               buf += 4;
-               result += 4;
-               size -= 4;
-               *pos += 4;
+                       value = ring->ring[(*pos - 12)/4];
+                       r = put_user(value, (uint32_t *)buf);
+                       if (r)
+                               return r;
+                       buf += 4;
+                       result += 4;
+                       size -= 4;
+                       *pos += 4;
+               }
+       } else {
+               p = early[0];
+               if (early[0] <= early[1])
+                       size = (early[1] - early[0]);
+               else
+                       size = ring->ring_size - (early[0] - early[1]);
+
+               while (size) {
+                       if (p == early[1])
+                               return result;
+
+                       value = ring->ring[p];
+                       r = put_user(value, (uint32_t *)buf);
+                       if (r)
+                               return r;
+
+                       buf += 4;
+                       result += 4;
+                       size--;
+                       p++;
+                       p &= ring->ptr_mask;
+               }
        }
 
        return result;
-- 
2.34.1