This is an RFC for adding documentation to IGT subtests. Each subtest can have
something similar to a WHAT - explaining what the subtest actually does,
and a WHY - which explains a use case, if applicable. Additionally,
include comments for anything in the subtest code which can help
explain HOW the test has been implemented. We don't actually need the WHAT
and WHY tags in the documentation.
These comments will not be linked to gtkdoc as of now, since we do not have a
mechanism to link it to every subtest name.
Signed-off-by: Vinay Belgaumkar <vinay.belgaumkar@xxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxxx>
Cc: Petri Latvala <petri.latvala@xxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
tests/gem_exec_basic.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)
diff --git a/tests/gem_exec_basic.c b/tests/gem_exec_basic.c
index 2f057ef..b1491cd 100644
--- a/tests/gem_exec_basic.c
+++ b/tests/gem_exec_basic.c
@@ -25,6 +25,11 @@
IGT_TEST_DESCRIPTION("Basic sanity check of execbuf-ioctl rings.");
+/*
+(WHAT) This subtest submits an empty batch to each ring and verifies
+that it is executed successfully
+(WHY) It validates that GT buffer submission mechanism is functional
+*/
static void noop(int fd, unsigned ring)
{
uint32_t bbe = MI_BATCH_BUFFER_END;
@@ -45,6 +50,11 @@ static void noop(int fd, unsigned ring)
gem_close(fd, exec.handle);
}
+/*
+(WHAT) This subtest memory maps a buffer, marks it as read only,
+and submits it to each ring for execution.
+(WHY) It helps us validate that the GT can execute read-only buffers
+*/
static void readonly(int fd, unsigned ring)
{
uint32_t bbe = MI_BATCH_BUFFER_END;
@@ -57,12 +67,15 @@ static void readonly(int fd, unsigned ring)
exec.handle = gem_create(fd, 4096);
gem_write(fd, exec.handle, 0, &bbe, sizeof(bbe));
+ /* Memory map a buffer and use it as the execbuf to be submitted */
execbuf = mmap(NULL, 4096, PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0);
igt_assert(execbuf != NULL);
execbuf->buffers_ptr = to_user_pointer(&exec);
execbuf->buffer_count = 1;
execbuf->flags = ring;
+
+ /* Now mark the buffer as read-only */
igt_assert(mprotect(execbuf, 4096, PROT_READ) == 0);
gem_execbuf(fd, execbuf);
@@ -70,6 +83,10 @@ static void readonly(int fd, unsigned ring)
gem_close(fd, exec.handle);
}
+/*
+(WHAT) Create a gtt mapped buffer and submit to the GPU.
+(WHY) It ensures GPU can properly map and access GTT mapped buffers
+*/
static void gtt(int fd, unsigned ring)
{
uint32_t bbe = MI_BATCH_BUFFER_END;
@@ -82,6 +99,8 @@ static void gtt(int fd, unsigned ring)
handle = gem_create(fd, 4096);
gem_set_domain(fd, handle, I915_GEM_DOMAIN_GTT, I915_GEM_DOMAIN_GTT);
+
+ /* Create a memory mapping through GTT */
execbuf = gem_mmap__gtt(fd, handle, 4096, PROT_WRITE);
exec = (struct drm_i915_gem_exec_object2 *)(execbuf + 1);
gem_close(fd, handle);
@@ -108,6 +127,8 @@ igt_main
fd = drm_open_driver(DRIVER_INTEL);
igt_require_gem(fd);
+ /* Start the hang detector process. Test will fail
+ if a GPU hang is detected during any subtest */
igt_fork_hang_detector(fd);
}
--
1.9.1
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