From: Douglas Anderson <dianders@chromium.org>
To: dri-devel@lists.freedesktop.org
Cc: tzimmermann@suse.de, linux-arm-msm@vger.kernel.org,
a.hajda@samsung.com, sam@ravnborg.org, airlied@linux.ie,
bjorn.andersson@linaro.org, daniel@ffwll.ch,
devicetree@vger.kernel.org, rodrigo.vivi@intel.com,
jonas@kwiboo.se, narmstrong@baylibre.com,
Laurent.pinchart@ideasonboard.com, robert.foss@linaro.org,
jernej.skrabec@gmail.com, mripard@kernel.org,
linus.walleij@linaro.org, maarten.lankhorst@linux.intel.com,
rajeevny@codeaurora.org, lyude@redhat.com,
thierry.reding@gmail.com, steev@kali.org,
Douglas Anderson <dianders@chromium.org>,
linux-kernel@vger.kernel.org
Subject: [PATCH 1/6] drm/dp: Don't zero PWMGEN_BIT_COUNT when driver_pwm_freq_hz not specified
Date: Wed, 28 Jul 2021 09:45:52 -0700 [thread overview]
Message-ID: <20210728094511.1.If017efce7116ae8ba015ed7def840c390a0e0c77@changeid> (raw)
In-Reply-To: <20210728164557.1882787-1-dianders@chromium.org>
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>
---
drivers/gpu/drm/drm_dp_helper.c | 10 ++++++----
1 file 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..b8a5c5e49d74 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) {
--
2.32.0.432.gabb21c7263-goog
next prev parent reply other threads:[~2021-07-28 16:46 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-28 16:45 [PATCH 0/6] drm/panel: atna33xc20: Fix the Samsung ATNA33XC20 panel Douglas Anderson
2021-07-28 16:45 ` Douglas Anderson [this message]
2021-07-28 16:45 ` [PATCH 2/6] drm/bridge: ti-sn65dsi86: Fix power off sequence Douglas Anderson
2021-07-29 11:47 ` Robert Foss
2021-07-28 16:45 ` [PATCH 3/6] drm/bridge: ti-sn65dsi86: Add some 100 us delays Douglas Anderson
2021-07-29 11:48 ` Robert Foss
2021-07-28 16:45 ` [PATCH 4/6] Revert "drm/panel-simple: Add Samsung ATNA33XC20" Douglas Anderson
2021-07-28 16:45 ` [PATCH 5/6] Revert "drm/panel-simple: Support for delays between GPIO & regulator" Douglas Anderson
2021-07-28 16:45 ` [PATCH 6/6] drm/panel: atna33xc20: Introduce the Samsung ATNA33XC20 panel Douglas Anderson
2021-07-29 19:42 ` [PATCH 0/6] drm/panel: atna33xc20: Fix " Sean Paul
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