drm/amd/display: Fix NULL dereference in dcn50/dcn60 init_hw

dc->clk_mgr is checked for NULL earlier in dcn50_init_hw() and
dcn60_init_hw(), but dcn50_initialize_min_clocks() and
dcn401_initialize_min_clocks() are called without any guard,
causing Smatch to report potential NULL dereferences.

Guard both call sites with the same pattern used throughout
both functions:

  if (dc->clk_mgr && dc->clk_mgr->funcs)

Also fix dcn50_initialize_min_clocks() which calls
get_dispclk_from_dentist without checking the function pointer,
unlike the dcn401 equivalent which guards that call.

Fix kernel-doc in dcn60_hwseq.c by adding missing parameter descriptions
for @probe in dcn60_update_probe_status() and @type in
is_probe_measurement_type_for_hubbub().

Fixes: 7f7d7ea1fa51 ("drm/amd/display: Add new sources for DCN6")
Reported-by: Dan Carpenter <error27@gmail.com>
Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Cc: Ivan Lipski <ivan.lipski@amd.com>
Cc: Dan Wheeler <daniel.wheeler@amd.com>
Cc: Roman Li <roman.li@amd.com>
Cc: Alex Hung <alex.hung@amd.com>
Cc: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 325c9a827cdd748e126eafeadaffc556204773d2)

drivers/gpu/drm/amd/display/dc/hwss/dcn50/dcn50_hwseq.c

diff --git a/drivers/gpu/drm/amd/display/dc/hwss/dcn50/dcn50_hwseq.c b/drivers/gpu/drm/amd/display/dc/hwss/dcn50/dcn50_hwseq.c
index a7f8fd0..e549556 100644
--- a/drivers/gpu/drm/amd/display/dc/hwss/dcn50/dcn50_hwseq.c
+++ b/drivers/gpu/drm/amd/display/dc/hwss/dcn50/dcn50_hwseq.c
@@ -67,7 +67,8 @@ static void dcn50_initialize_min_clocks(struct dc *dc)
 		 * audio corruption. Read current DISPCLK from DENTIST and request the same
 		 * freq to ensure that the timing is valid and unchanged.
 		 */
-		clocks->dispclk_khz = dc->clk_mgr->funcs->get_dispclk_from_dentist(dc->clk_mgr);
+		if (dc->clk_mgr->funcs->get_dispclk_from_dentist)
+			clocks->dispclk_khz = dc->clk_mgr->funcs->get_dispclk_from_dentist(dc->clk_mgr);
 	}
 	clocks->ref_dtbclk_khz = dc->clk_mgr->bw_params->clk_table.entries[0].dtbclk_mhz * 1000;
 	clocks->fclk_p_state_change_support = true;
@@ -639,7 +640,8 @@ void dcn50_init_hw(struct dc *dc)
 			dc->res_pool->hubbub->funcs->allow_self_refresh_control(dc->res_pool->hubbub,
 					!dc->res_pool->hubbub->ctx->dc->debug.disable_stutter);
 
-		dcn50_initialize_min_clocks(dc);
+		if (dc->clk_mgr && dc->clk_mgr->funcs)
+			dcn50_initialize_min_clocks(dc);
 
 		/* On HW init, allow idle optimizations after pipes have been turned off.
 		 *

drivers/gpu/drm/amd/display/dc/hwss/dcn60/dcn60_hwseq.c

diff --git a/drivers/gpu/drm/amd/display/dc/hwss/dcn60/dcn60_hwseq.c b/drivers/gpu/drm/amd/display/dc/hwss/dcn60/dcn60_hwseq.c
index 72c2d3c..61ad6ef 100644
--- a/drivers/gpu/drm/amd/display/dc/hwss/dcn60/dcn60_hwseq.c
+++ b/drivers/gpu/drm/amd/display/dc/hwss/dcn60/dcn60_hwseq.c
@@ -643,7 +643,8 @@ void dcn60_init_hw(struct dc *dc)
 			dc->res_pool->hubbub->funcs->allow_self_refresh_control(dc->res_pool->hubbub,
 				!dc->res_pool->hubbub->ctx->dc->debug.disable_stutter);
 
-		dcn401_initialize_min_clocks(dc);
+		if (dc->clk_mgr && dc->clk_mgr->funcs)
+			dcn401_initialize_min_clocks(dc);
 
 		/* On HW init, allow idle optimizations after pipes have been turned off.
 		 *
@@ -1001,6 +1002,7 @@ static void dcn60_build_hubbub_perfmon_sequence(
 /**
  * dcn60_update_probe_status - Set the valid flag on a latched probe result.
  * @status: result sink whose u was written by the GET BLS step during execute
+ * @probe: current probe state used to determine measurement type and validity
  */
 static void dcn60_update_probe_status(struct dc_probe_status *status)
 {
@@ -1024,6 +1026,7 @@ static void dcn60_update_probe_status(struct dc_probe_status *status)
 /**
  * is_probe_measurement_type_for_hubbub - Returns true if the probe type is
  * served by the hubbub perfmon block on DCN60.
+ * @type: the probe measurement type to classify
  */
 static bool is_probe_measurement_type_for_hubbub(enum dc_probe_type type)
 {