From: Harry Wentland harry.wentland@amd.com

On Carrizo/Stoney systems we set backlight through panel_cntl, i.e. directly via the PWM registers, if DMCU is not initialized. We always read it back through ABM registers which leads to a mismatch and forces atomic_commit to program the backlight each time.

Instead make sure we use the same logic for backlight readback, i.e. read it from panel_cntl if DMCU is not initialized.

We also need to remove some extraneous and incorrect calculations at the end of dce_get_16_bit_backlight_from_pwm.

Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1666 Cc: stable@vger.kernel.org

Reviewed-by: Josip Pavic josip.pavic@amd.com Acked-by: Mikita Lipski mikita.lipski@amd.com Signed-off-by: Harry Wentland harry.wentland@amd.com --- drivers/gpu/drm/amd/display/dc/core/dc_link.c | 16 ++++++++++++---- .../gpu/drm/amd/display/dc/dce/dce_panel_cntl.c | 10 ---------- 2 files changed, 12 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link.c b/drivers/gpu/drm/amd/display/dc/core/dc_link.c index 3c3637fcc2b8..7928852185b8 100644 --- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c +++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c @@ -2586,13 +2586,21 @@ static struct abm *get_abm_from_stream_res(const struct dc_link *link)

int dc_link_get_backlight_level(const struct dc_link *link) { - struct abm *abm = get_abm_from_stream_res(link); + struct panel_cntl *panel_cntl = link->panel_cntl; + struct dc *dc = link->ctx->dc; + struct dmcu *dmcu = dc->res_pool->dmcu; + bool fw_set_brightness = true;

- if (abm == NULL || abm->funcs->get_current_backlight == NULL) - return DC_ERROR_UNEXPECTED; + if (dmcu) + fw_set_brightness = dmcu->funcs->is_dmcu_initialized(dmcu);

- return (int) abm->funcs->get_current_backlight(abm); + if (!fw_set_brightness && panel_cntl->funcs->get_current_backlight) + return panel_cntl->funcs->get_current_backlight(panel_cntl); + else if (abm != NULL && abm->funcs->get_current_backlight != NULL) + return (int) abm->funcs->get_current_backlight(abm); + else + return DC_ERROR_UNEXPECTED; }

int dc_link_get_target_backlight_pwm(const struct dc_link *link) diff --git a/drivers/gpu/drm/amd/display/dc/dce/dce_panel_cntl.c b/drivers/gpu/drm/amd/display/dc/dce/dce_panel_cntl.c index e92339235863..e8570060d007 100644 --- a/drivers/gpu/drm/amd/display/dc/dce/dce_panel_cntl.c +++ b/drivers/gpu/drm/amd/display/dc/dce/dce_panel_cntl.c @@ -49,7 +49,6 @@ static unsigned int dce_get_16_bit_backlight_from_pwm(struct panel_cntl *panel_cntl) { uint64_t current_backlight; - uint32_t round_result; uint32_t bl_period, bl_int_count; uint32_t bl_pwm, fractional_duty_cycle_en; uint32_t bl_period_mask, bl_pwm_mask; @@ -84,15 +83,6 @@ static unsigned int dce_get_16_bit_backlight_from_pwm(struct panel_cntl *panel_c current_backlight = div_u64(current_backlight, bl_period); current_backlight = (current_backlight + 1) >> 1;

- current_backlight = (uint64_t)(current_backlight) * bl_period; - - round_result = (uint32_t)(current_backlight & 0xFFFFFFFF); - - round_result = (round_result >> (bl_int_count-1)) & 1; - - current_backlight >>= bl_int_count; - current_backlight += round_result; - return (uint32_t)(current_backlight); }