drm/amd/display: Get backlight from PWM if DMCU is not initialized

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>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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 3c8eb3e659af12ebdb94036bc1008c3e94e580a6..61e49671fed5e197303113813f61c1d2bdff3d54 100644 (file)
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
@@ -2752,13 +2752,21 @@ 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 e9233923586316349952ad5dc9914be364044a74..e8570060d007ba5bab0db3b3395aca2b9c487573 100644 (file)
--- 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);
 }