[Why] Brightness programming may involve a conversion of a user requested brightness against what was in a custom brightness curve. The values might not match what a user programmed.
[How] Add a new trace event to show specific converted brightness values. Signed-off-by: Mario Limonciello <[email protected]> --- Documentation/gpu/amdgpu/debugging.rst | 18 +++++++++++++ .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 8 ++++++ .../amd/display/amdgpu_dm/amdgpu_dm_trace.h | 26 +++++++++++++++++++ 3 files changed, 52 insertions(+) diff --git a/Documentation/gpu/amdgpu/debugging.rst b/Documentation/gpu/amdgpu/debugging.rst index 7cbfea0606e1..ac914d524741 100644 --- a/Documentation/gpu/amdgpu/debugging.rst +++ b/Documentation/gpu/amdgpu/debugging.rst @@ -85,3 +85,21 @@ UMR GPU debugging and diagnostics tool. Please see the umr `documentation <https://umr.readthedocs.io/en/main/>`_ for more information about its capabilities. + +Debugging backlight brightness +============================== +Default backlight brightness is intended to be set via the policy advertised +by the firmware. Firmware will often provide different defaults for AC or DC. +Furthermore, some userspace software will save backlight brightness during +the previous boot and attempt to restore it. + +Some firmware also has support for a feature called "Custom Backlight Curves" +where an input value for brightness is mapped along a linearly interpolated +curve of brightness values that better match display characteristics. + +In the event of problems happening with backlight, there is a trace event +that can be enabled at bootup to log every brightness change request. +This can help isolate where the problem is. To enable the trace event add +the following to the kernel command line: + + tp_printk trace_event=amdgpu_dm:amdgpu_dm_brightness:mod:amdgpu trace_buf_size=1M diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c index 77302caaf24a..2ac5cd225781 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c @@ -4860,6 +4860,14 @@ static void amdgpu_dm_backlight_set_level(struct amdgpu_display_manager *dm, reallow_idle = true; } + if (trace_amdgpu_dm_brightness_enabled()) { + trace_amdgpu_dm_brightness(__builtin_return_address(0), + user_brightness, + brightness, + caps->aux_support, + power_supply_is_system_supplied() > 0); + } + if (caps->aux_support) { rc = dc_link_set_backlight_level_nits(link, true, brightness, AUX_BL_DEFAULT_TRANSITION_TIME_MS); diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h index 4686d4b0cbad..308a36176bd2 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h @@ -726,6 +726,32 @@ TRACE_EVENT(dcn_optc_lock_unlock_state, ) ); +TRACE_EVENT(amdgpu_dm_brightness, + TP_PROTO(void *function, u32 user_brightness, u32 converted_brightness, bool aux, bool ac), + TP_ARGS(function, user_brightness, converted_brightness, aux, ac), + TP_STRUCT__entry( + __field(void *, function) + __field(u32, user_brightness) + __field(u32, converted_brightness) + __field(bool, aux) + __field(bool, ac) + ), + TP_fast_assign( + __entry->function = function; + __entry->user_brightness = user_brightness; + __entry->converted_brightness = converted_brightness; + __entry->aux = aux; + __entry->ac = ac; + ), + TP_printk("%ps: brightness requested=%u converted=%u aux=%s power=%s", + (void *)__entry->function, + (u32)__entry->user_brightness, + (u32)__entry->converted_brightness, + (__entry->aux) ? "true" : "false", + (__entry->ac) ? "AC" : "DC" + ) +); + #endif /* _AMDGPU_DM_TRACE_H_ */ #undef TRACE_INCLUDE_PATH -- 2.49.0
