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| author | Douglas Anderson <dianders@chromium.org> | 2021-07-30 18:46:00 +0300 |
|---|---|---|
| committer | Sam Ravnborg <sam@ravnborg.org> | 2021-07-31 21:02:59 +0300 |
| commit | 64c0274fb15c1daf6618f5f4d2b3ed80822e5e8d (patch) | |
| tree | 2c5c8b9220ee4627b6a60e6c5ec1bb753d900321 /drivers/gpu/drm/drm_dp_helper.c | |
| parent | 676f11b5a4a06281420070ffdbb09c05851fa819 (diff) | |
| download | linux-64c0274fb15c1daf6618f5f4d2b3ed80822e5e8d.tar.xz | |
drm/dp: Don't zero PWMGEN_BIT_COUNT when driver_pwm_freq_hz not specified
The function drm_edp_backlight_init() is defined such that the
"driver_pwm_freq_hz" parameter is optional--it's 0 if you don't want
to futz with it. If you follow this variable through, you'll find out
that if it's 0 we won't ever set the "bl->pwmgen_bit_count", leaving
it as 0.
That means that before using it in drm_edp_backlight_enable() we need
to check to see if it's non-zero.
Programming this field to zero was confusing the panel I tested with
(Samsung ATNA33XC20). The backlight still worked somewhat but the
brightness values didn't correspond to what they should have been.
Fixes: 867cf9cd73c3 ("drm/dp: Extract i915's eDP backlight code into DRM helpers")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210730084534.v2.1.If017efce7116ae8ba015ed7def840c390a0e0c77@changeid
Diffstat (limited to 'drivers/gpu/drm/drm_dp_helper.c')
| -rw-r--r-- | drivers/gpu/drm/drm_dp_helper.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index b5f75ca05774..2b6c35965459 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -3229,10 +3229,12 @@ int drm_edp_backlight_enable(struct drm_dp_aux *aux, const struct drm_edp_backli new_dpcd_buf &= ~DP_EDP_BACKLIGHT_CONTROL_MODE_MASK; new_dpcd_buf |= DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD; - ret = drm_dp_dpcd_writeb(aux, DP_EDP_PWMGEN_BIT_COUNT, bl->pwmgen_bit_count); - if (ret != 1) - drm_dbg_kms(aux->drm_dev, "%s: Failed to write aux pwmgen bit count: %d\n", - aux->name, ret); + if (bl->pwmgen_bit_count) { + ret = drm_dp_dpcd_writeb(aux, DP_EDP_PWMGEN_BIT_COUNT, bl->pwmgen_bit_count); + if (ret != 1) + drm_dbg_kms(aux->drm_dev, "%s: Failed to write aux pwmgen bit count: %d\n", + aux->name, ret); + } } if (bl->pwm_freq_pre_divider) { |