drm/dp_mst: Add kunit tests for drm_dp_get_vc_payload_bw()

Add kunit test cases for drm_dp_get_vc_payload_bw() with all the DP1.4
and UHBR link configurations.

v2:
- List test cases in decreasing rate,lane count order matching the
  corresponding DP Standard tables. (Ville)
- Add references to the DP Standard tables.
v3:
- Sort the testcases properly.
v4:
- Avoid 'stack frame size x exceeds limit y in
  drm_test_dp_mst_calc_pbn_div()' compiler warn. (LKP)

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Lyude Paul <lyude@redhat.com>
Cc: dri-devel@lists.freedesktop.org
Cc: kernel test robot <lkp@intel.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> (v3)
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231120125256.2433782-1-imre.deak@intel.com

diff --git a/drivers/gpu/drm/tests/drm_dp_mst_helper_test.c b/drivers/gpu/drm/tests/drm_dp_mst_helper_test.c
index e3c818d..d916e54 100644 (file)
--- a/drivers/gpu/drm/tests/drm_dp_mst_helper_test.c
+++ b/drivers/gpu/drm/tests/drm_dp_mst_helper_test.c
@@ -68,6 +68,152 @@ static void dp_mst_calc_pbn_mode_desc(const struct drm_dp_mst_calc_pbn_mode_test
 KUNIT_ARRAY_PARAM(drm_dp_mst_calc_pbn_mode, drm_dp_mst_calc_pbn_mode_cases,
                  dp_mst_calc_pbn_mode_desc);
 
+struct drm_dp_mst_calc_pbn_div_test {
+       int link_rate;
+       int lane_count;
+       fixed20_12 expected;
+};
+
+#define fp_init(__int, __frac) { \
+       .full = (__int) * (1 << 12) + \
+               (__frac) * (1 << 12) / 100000 \
+}
+
+static const struct drm_dp_mst_calc_pbn_div_test drm_dp_mst_calc_pbn_div_dp1_4_cases[] = {
+       /*
+        * UHBR rates (DP Standard v2.1 2.7.6.3, specifying the rounded to
+        *             closest value to 2 decimal places):
+        * .expected = .link_rate * .lane_count * 0.9671 / 8 / 54 / 100
+        * DP1.4 rates (DP Standard v2.1 2.6.4.2):
+        * .expected = .link_rate * .lane_count * 0.8000 / 8 / 54 / 100
+        *
+        * truncated to 5 decimal places.
+        */
+       {
+               .link_rate = 2000000,
+               .lane_count = 4,
+               .expected = fp_init(179,  9259),  /* 179.09259 */
+       },
+       {
+               .link_rate = 2000000,
+               .lane_count = 2,
+               .expected = fp_init(89, 54629),
+       },
+       {
+               .link_rate = 2000000,
+               .lane_count = 1,
+               .expected = fp_init(44, 77314),
+       },
+       {
+               .link_rate = 1350000,
+               .lane_count = 4,
+               .expected = fp_init(120, 88750),
+       },
+       {
+               .link_rate = 1350000,
+               .lane_count = 2,
+               .expected = fp_init(60, 44375),
+       },
+       {
+               .link_rate = 1350000,
+               .lane_count = 1,
+               .expected = fp_init(30, 22187),
+       },
+       {
+               .link_rate = 1000000,
+               .lane_count = 4,
+               .expected = fp_init(89, 54629),
+       },
+       {
+               .link_rate = 1000000,
+               .lane_count = 2,
+               .expected = fp_init(44, 77314),
+       },
+       {
+               .link_rate = 1000000,
+               .lane_count = 1,
+               .expected = fp_init(22, 38657),
+       },
+       {
+               .link_rate = 810000,
+               .lane_count = 4,
+               .expected = fp_init(60, 0),
+       },
+       {
+               .link_rate = 810000,
+               .lane_count = 2,
+               .expected = fp_init(30, 0),
+       },
+       {
+               .link_rate = 810000,
+               .lane_count = 1,
+               .expected = fp_init(15, 0),
+       },
+       {
+               .link_rate = 540000,
+               .lane_count = 4,
+               .expected = fp_init(40, 0),
+       },
+       {
+               .link_rate = 540000,
+               .lane_count = 2,
+               .expected = fp_init(20, 0),
+       },
+       {
+               .link_rate = 540000,
+               .lane_count = 1,
+               .expected = fp_init(10, 0),
+       },
+       {
+               .link_rate = 270000,
+               .lane_count = 4,
+               .expected = fp_init(20, 0),
+       },
+       {
+               .link_rate = 270000,
+               .lane_count = 2,
+               .expected = fp_init(10, 0),
+       },
+       {
+               .link_rate = 270000,
+               .lane_count = 1,
+               .expected = fp_init(5, 0),
+       },
+       {
+               .link_rate = 162000,
+               .lane_count = 4,
+               .expected = fp_init(12, 0),
+       },
+       {
+               .link_rate = 162000,
+               .lane_count = 2,
+               .expected = fp_init(6, 0),
+       },
+       {
+               .link_rate = 162000,
+               .lane_count = 1,
+               .expected = fp_init(3, 0),
+       },
+};
+
+static void drm_test_dp_mst_calc_pbn_div(struct kunit *test)
+{
+       const struct drm_dp_mst_calc_pbn_div_test *params = test->param_value;
+       /* mgr->dev is only needed by drm_dbg_kms(), but it's not called for the test cases. */
+       struct drm_dp_mst_topology_mgr *mgr = test->priv;
+
+       KUNIT_EXPECT_EQ(test, drm_dp_get_vc_payload_bw(mgr, params->link_rate, params->lane_count).full,
+                       params->expected.full);
+}
+
+static void dp_mst_calc_pbn_div_desc(const struct drm_dp_mst_calc_pbn_div_test *t, char *desc)
+{
+       sprintf(desc, "Link rate %d lane count %d", t->link_rate, t->lane_count);
+}
+
+KUNIT_ARRAY_PARAM(drm_dp_mst_calc_pbn_div, drm_dp_mst_calc_pbn_div_dp1_4_cases,
+                 dp_mst_calc_pbn_div_desc);
+
 static u8 data[] = { 0xff, 0x00, 0xdd };
 
 struct drm_dp_mst_sideband_msg_req_test {
@@ -416,13 +562,27 @@ KUNIT_ARRAY_PARAM(drm_dp_mst_sideband_msg_req, drm_dp_mst_sideband_msg_req_cases
 
 static struct kunit_case drm_dp_mst_helper_tests[] = {
        KUNIT_CASE_PARAM(drm_test_dp_mst_calc_pbn_mode, drm_dp_mst_calc_pbn_mode_gen_params),
+       KUNIT_CASE_PARAM(drm_test_dp_mst_calc_pbn_div, drm_dp_mst_calc_pbn_div_gen_params),
        KUNIT_CASE_PARAM(drm_test_dp_mst_sideband_msg_req_decode,
                         drm_dp_mst_sideband_msg_req_gen_params),
        { }
 };
 
+static int drm_dp_mst_helper_tests_init(struct kunit *test)
+{
+       struct drm_dp_mst_topology_mgr *mgr;
+
+       mgr = kunit_kzalloc(test, sizeof(*mgr), GFP_KERNEL);
+       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, mgr);
+
+       test->priv = mgr;
+
+       return 0;
+}
+
 static struct kunit_suite drm_dp_mst_helper_test_suite = {
        .name = "drm_dp_mst_helper",
+       .init = drm_dp_mst_helper_tests_init,
        .test_cases = drm_dp_mst_helper_tests,
 };