drm/amdgpu: initialize iter.start in amdgpu_devcoredump_format

This fixes read /sys/class/drm/cardN/device/devcoredump/data
return empty content sometimes.

amdgpu_devcoredump_format() leaves struct drm_print_iterator's
.start field uninitialized on the stack before passing it to
drm_coredump_printer(). __drm_puts_coredump() compares the running
.offset against .start to decide whether to skip or copy each
chunk:

	if (iterator->offset < iterator->start) {
		if (iterator->offset + len <= iterator->start) {
			iterator->offset += len;
			return;
		}
		...
	}

Fixes: 4bbba79a7f1d ("drm/amdgpu: move devcoredump generation to a worker")
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Qiang Yu <Qiang.Yu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dev_coredump.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_dev_coredump.c
index 27830518a230..bed68f0c3080 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dev_coredump.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dev_coredump.c
@@ -229,6 +229,7 @@ amdgpu_devcoredump_format(char *buffer, size_t count, struct amdgpu_coredump_inf
 
 	sizing_pass = buffer == NULL;
 	iter.data = buffer;
+	iter.start = 0;
 	iter.offset = 0;
 	iter.remain = count;