drivers/gpu/drm/amd/amdgpu/../display/dc/dce110/dce110_hw_sequencer.c:1018 dce110_edp_backlight_control() error: we previously assumed 'link->panel_cntl' could be null (see line 977)

From: Dan Carpenter
Date: Thu Mar 03 2022 - 06:47:06 EST

tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: 719fce7539cd3e186598e2aed36325fe892150cf
commit: 06ddcee49a35981835e04910bef462a09f108984 drm/amd/display: Added multi instance support for panel control
config: powerpc-randconfig-m031-20220301 (https://download.01.org/0day-ci/archive/20220302/202203020137.M32nCNIJ-lkp@xxxxxxxxx/config)
compiler: powerpc-linux-gcc (GCC) 11.2.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

smatch warnings:
drivers/gpu/drm/amd/amdgpu/../display/dc/dce110/dce110_hw_sequencer.c:1018 dce110_edp_backlight_control() error: we previously assumed 'link->panel_cntl' could be null (see line 977)

vim +1018 drivers/gpu/drm/amd/amdgpu/../display/dc/dce110/dce110_hw_sequencer.c

8a31820b12187c7 Martin Leung 2019-07-09 963 void dce110_edp_backlight_control(
5eefbc40173644b Yue Hin Lau 2017-09-15 964 struct dc_link *link,
5eefbc40173644b Yue Hin Lau 2017-09-15 965 bool enable)
5eefbc40173644b Yue Hin Lau 2017-09-15 966 {
069d418f412ec4b Andrew Jiang 2017-09-26 967 struct dc_context *ctx = link->ctx;
5eefbc40173644b Yue Hin Lau 2017-09-15 968 struct bp_transmitter_control cntl = { 0 };
06ddcee49a35981 Jake Wang 2021-02-23 969 uint8_t panel_instance;
5eefbc40173644b Yue Hin Lau 2017-09-15 970
069d418f412ec4b Andrew Jiang 2017-09-26 971 if (dal_graphics_object_id_get_connector_id(link->link_enc->connector)
5eefbc40173644b Yue Hin Lau 2017-09-15 972 != CONNECTOR_ID_EDP) {
5eefbc40173644b Yue Hin Lau 2017-09-15 973 BREAK_TO_DEBUGGER();
5eefbc40173644b Yue Hin Lau 2017-09-15 974 return;
5eefbc40173644b Yue Hin Lau 2017-09-15 975 }
5eefbc40173644b Yue Hin Lau 2017-09-15 976
014427adc5565a0 Sherry 2020-11-11 @977 if (link->panel_cntl) {
^^^^^^^^^^^^^^^^
This code assumes "link->panel_cntl" can be NULL

014427adc5565a0 Sherry 2020-11-11 978 bool is_backlight_on = link->panel_cntl->funcs->is_panel_backlight_on(link->panel_cntl);
014427adc5565a0 Sherry 2020-11-11 979
014427adc5565a0 Sherry 2020-11-11 980 if ((enable && is_backlight_on) || (!enable && !is_backlight_on)) {
1296423bf23c7a5 Bhawanpreet Lakha 2018-02-20 981 DC_LOG_HW_RESUME_S3(
014427adc5565a0 Sherry 2020-11-11 982 "%s: panel already powered up/off. Do nothing.\n",
5eefbc40173644b Yue Hin Lau 2017-09-15 983 __func__);
5eefbc40173644b Yue Hin Lau 2017-09-15 984 return;
5eefbc40173644b Yue Hin Lau 2017-09-15 985 }
014427adc5565a0 Sherry 2020-11-11 986 }
5eefbc40173644b Yue Hin Lau 2017-09-15 987
5eefbc40173644b Yue Hin Lau 2017-09-15 988 /* Send VBIOS command to control eDP panel backlight */
5eefbc40173644b Yue Hin Lau 2017-09-15 989
1296423bf23c7a5 Bhawanpreet Lakha 2018-02-20 990 DC_LOG_HW_RESUME_S3(
5eefbc40173644b Yue Hin Lau 2017-09-15 991 "%s: backlight action: %s\n",
5eefbc40173644b Yue Hin Lau 2017-09-15 992 __func__, (enable ? "On":"Off"));
5eefbc40173644b Yue Hin Lau 2017-09-15 993
5eefbc40173644b Yue Hin Lau 2017-09-15 994 cntl.action = enable ?
5eefbc40173644b Yue Hin Lau 2017-09-15 995 TRANSMITTER_CONTROL_BACKLIGHT_ON :
5eefbc40173644b Yue Hin Lau 2017-09-15 996 TRANSMITTER_CONTROL_BACKLIGHT_OFF;
8740196935625df Andrew Jiang 2017-09-25 997
5eefbc40173644b Yue Hin Lau 2017-09-15 998 /*cntl.engine_id = ctx->engine;*/
5eefbc40173644b Yue Hin Lau 2017-09-15 999 cntl.transmitter = link->link_enc->transmitter;
5eefbc40173644b Yue Hin Lau 2017-09-15 1000 cntl.connector_obj_id = link->link_enc->connector;
5eefbc40173644b Yue Hin Lau 2017-09-15 1001 /*todo: unhardcode*/
5eefbc40173644b Yue Hin Lau 2017-09-15 1002 cntl.lanes_number = LANE_COUNT_FOUR;
5eefbc40173644b Yue Hin Lau 2017-09-15 1003 cntl.hpd_sel = link->link_enc->hpd_source;
cf1835f03ffb3b5 Charlene Liu 2018-01-08 1004 cntl.signal = SIGNAL_TYPE_EDP;
5eefbc40173644b Yue Hin Lau 2017-09-15 1005
5eefbc40173644b Yue Hin Lau 2017-09-15 1006 /* For eDP, the following delays might need to be considered
5eefbc40173644b Yue Hin Lau 2017-09-15 1007 * after link training completed:
5eefbc40173644b Yue Hin Lau 2017-09-15 1008 * idle period - min. accounts for required BS-Idle pattern,
5eefbc40173644b Yue Hin Lau 2017-09-15 1009 * max. allows for source frame synchronization);
5eefbc40173644b Yue Hin Lau 2017-09-15 1010 * 50 msec max. delay from valid video data from source
5eefbc40173644b Yue Hin Lau 2017-09-15 1011 * to video on dislpay or backlight enable.
5eefbc40173644b Yue Hin Lau 2017-09-15 1012 *
5eefbc40173644b Yue Hin Lau 2017-09-15 1013 * Disable the delay for now.
5eefbc40173644b Yue Hin Lau 2017-09-15 1014 * Enable it in the future if necessary.
5eefbc40173644b Yue Hin Lau 2017-09-15 1015 */
5eefbc40173644b Yue Hin Lau 2017-09-15 1016 /* dc_service_sleep_in_milliseconds(50); */
5180d4a4766d7df Charlene Liu 2018-01-18 1017 /*edp 1.2*/
06ddcee49a35981 Jake Wang 2021-02-23 @1018 panel_instance = link->panel_cntl->inst;
^^^^^^^^^^^^^^^^^^
Unchecked dereference.

5180d4a4766d7df Charlene Liu 2018-01-18 1019 if (cntl.action == TRANSMITTER_CONTROL_BACKLIGHT_ON)
5180d4a4766d7df Charlene Liu 2018-01-18 1020 edp_receiver_ready_T7(link);
8a0e210c048e97f Chris Park 2020-08-05 1021
8a0e210c048e97f Chris Park 2020-08-05 1022 if (ctx->dc->ctx->dmub_srv &&
8a0e210c048e97f Chris Park 2020-08-05 1023 ctx->dc->debug.dmub_command_table) {
8a0e210c048e97f Chris Park 2020-08-05 1024 if (cntl.action == TRANSMITTER_CONTROL_BACKLIGHT_ON)
8a0e210c048e97f Chris Park 2020-08-05 1025 ctx->dc_bios->funcs->enable_lvtma_control(ctx->dc_bios,
06ddcee49a35981 Jake Wang 2021-02-23 1026 LVTMA_CONTROL_LCD_BLON,
06ddcee49a35981 Jake Wang 2021-02-23 1027 panel_instance);
8a0e210c048e97f Chris Park 2020-08-05 1028 else
8a0e210c048e97f Chris Park 2020-08-05 1029 ctx->dc_bios->funcs->enable_lvtma_control(ctx->dc_bios,
06ddcee49a35981 Jake Wang 2021-02-23 1030 LVTMA_CONTROL_LCD_BLOFF,
06ddcee49a35981 Jake Wang 2021-02-23 1031 panel_instance);
8a0e210c048e97f Chris Park 2020-08-05 1032 }
8a0e210c048e97f Chris Park 2020-08-05 1033
069d418f412ec4b Andrew Jiang 2017-09-26 1034 link_transmitter_control(ctx->dc_bios, &cntl);
96577cf82a13317 Hersen Wu 2020-01-14 1035
96577cf82a13317 Hersen Wu 2020-01-14 1036 if (enable && link->dpcd_sink_ext_caps.bits.oled)
96577cf82a13317 Hersen Wu 2020-01-14 1037 msleep(OLED_POST_T7_DELAY);
96577cf82a13317 Hersen Wu 2020-01-14 1038
96577cf82a13317 Hersen Wu 2020-01-14 1039 if (link->dpcd_sink_ext_caps.bits.oled ||
96577cf82a13317 Hersen Wu 2020-01-14 1040 link->dpcd_sink_ext_caps.bits.hdr_aux_backlight_control == 1 ||
96577cf82a13317 Hersen Wu 2020-01-14 1041 link->dpcd_sink_ext_caps.bits.sdr_aux_backlight_control == 1)
96577cf82a13317 Hersen Wu 2020-01-14 1042 dc_link_backlight_enable_aux(link, enable);
96577cf82a13317 Hersen Wu 2020-01-14 1043
69b9723a81e74e5 Charlene Liu 2018-01-18 1044 /*edp 1.2*/
5180d4a4766d7df Charlene Liu 2018-01-18 1045 if (cntl.action == TRANSMITTER_CONTROL_BACKLIGHT_OFF)
3a372bed1e337ef Hugo Hu 2020-10-06 1046 edp_add_delay_for_T9(link);
96577cf82a13317 Hersen Wu 2020-01-14 1047
96577cf82a13317 Hersen Wu 2020-01-14 1048 if (!enable && link->dpcd_sink_ext_caps.bits.oled)
96577cf82a13317 Hersen Wu 2020-01-14 1049 msleep(OLED_PRE_T11_DELAY);
5eefbc40173644b Yue Hin Lau 2017-09-15 1050 }

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx