drm/mst: remove mgr parameter and debug logging from drm_dp_get_vc_payload_bw()

The struct drm_dp_mst_topology_mgr *mgr parameter is only used for debug
logging in case the passed in link rate or lane count are zero. There's
no further error checking as such, and the function returns 0.

There should be no case where the parameters are zero. The returned
value is generally used as a divisor, and if we were hitting this, we'd
be seeing division by zero.

Just remove the debug logging altogether, along with the mgr parameter,
so that the function can be used in non-MST contexts without the
topology manager.

v2: Also remove drm_dp_mst_helper_tests_init as unnecessary (Imre)

Cc: Imre Deak <[email protected]>
Cc: Lyude Paul <[email protected]>
Reviewed-by: Imre Deak <[email protected]>
Acked-by: Maxime Ripard <[email protected]>
Acked-by: Thomas Zimmermann <[email protected]>
Signed-off-by: Jani Nikula <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/72d77e7a7fe69c784e9df048b7e6f250fd7599e4.1735912293.git.jani.nikula@intel.com

Author: jnikula

drivers/gpu/drm/display/drm_dp_mst_topology.c

@@ -3572,8 +3572,7 @@ static int drm_dp_send_up_ack_reply(struct drm_dp_mst_topology_mgr *mgr,
 }
 
 /**
- * drm_dp_get_vc_payload_bw - get the VC payload BW for an MST link
- * @mgr: The &drm_dp_mst_topology_mgr to use
+ * drm_dp_get_vc_payload_bw - get the VC payload BW for an MTP link
  * @link_rate: link rate in 10kbits/s units
  * @link_lane_count: lane count
  *
@@ -3584,17 +3583,12 @@ static int drm_dp_send_up_ack_reply(struct drm_dp_mst_topology_mgr *mgr,
  *
  * Returns the BW / timeslot value in 20.12 fixed point format.
  */
-fixed20_12 drm_dp_get_vc_payload_bw(const struct drm_dp_mst_topology_mgr *mgr,
-				    int link_rate, int link_lane_count)
+fixed20_12 drm_dp_get_vc_payload_bw(int link_rate, int link_lane_count)
 {
 	int ch_coding_efficiency =
 		drm_dp_bw_channel_coding_efficiency(drm_dp_is_uhbr_rate(link_rate));
 	fixed20_12 ret;
 
-	if (link_rate == 0 || link_lane_count == 0)
-		drm_dbg_kms(mgr->dev, "invalid link rate/lane count: (%d / %d)\n",
-			    link_rate, link_lane_count);
-
 	/* See DP v2.0 2.6.4.2, 2.7.6.3 VCPayload_Bandwidth_for_OneTimeSlotPer_MTP_Allocation */
 	ret.full = DIV_ROUND_DOWN_ULL(mul_u32_u32(link_rate * link_lane_count,
 						  ch_coding_efficiency),

drivers/gpu/drm/i915/display/intel_dp_mst.c

@@ -244,8 +244,7 @@ static int mst_stream_find_vcpi_slots_for_bpp(struct intel_dp *intel_dp,
 		crtc_state->fec_enable = !intel_dp_is_uhbr(crtc_state);
 	}
 
-	mst_state->pbn_div = drm_dp_get_vc_payload_bw(&intel_dp->mst_mgr,
-						      crtc_state->port_clock,
+	mst_state->pbn_div = drm_dp_get_vc_payload_bw(crtc_state->port_clock,
 						      crtc_state->lane_count);
 
 	max_dpt_bpp = intel_dp_mst_max_dpt_bpp(crtc_state, dsc);

drivers/gpu/drm/nouveau/dispnv50/disp.c

@@ -992,8 +992,7 @@ nv50_msto_atomic_check(struct drm_encoder *encoder,
 	if (!mst_state->pbn_div.full) {
 		struct nouveau_encoder *outp = mstc->mstm->outp;
 
-		mst_state->pbn_div = drm_dp_get_vc_payload_bw(&mstm->mgr,
-							      outp->dp.link_bw, outp->dp.link_nr);
+		mst_state->pbn_div = drm_dp_get_vc_payload_bw(outp->dp.link_bw, outp->dp.link_nr);
 	}
 
 	slots = drm_dp_atomic_find_time_slots(state, &mstm->mgr, mstc->port, asyh->dp.pbn);

drivers/gpu/drm/tests/drm_dp_mst_helper_test.c

@@ -199,10 +199,8 @@ static const struct drm_dp_mst_calc_pbn_div_test drm_dp_mst_calc_pbn_div_dp1_4_c
 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,
+	KUNIT_EXPECT_EQ(test, drm_dp_get_vc_payload_bw(params->link_rate, params->lane_count).full,
 			params->expected.full);
 }
 
@@ -568,21 +566,8 @@ static struct kunit_case drm_dp_mst_helper_tests[] = {
 	{ }
 };
 
-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,
 };
 

include/drm/display/drm_dp_mst_helper.h

@@ -867,8 +867,7 @@ struct edid *drm_dp_mst_get_edid(struct drm_connector *connector,
 				 struct drm_dp_mst_topology_mgr *mgr,
 				 struct drm_dp_mst_port *port);
 
-fixed20_12 drm_dp_get_vc_payload_bw(const struct drm_dp_mst_topology_mgr *mgr,
-				    int link_rate, int link_lane_count);
+fixed20_12 drm_dp_get_vc_payload_bw(int link_rate, int link_lane_count);
 
 int drm_dp_calc_pbn_mode(int clock, int bpp);