[PATCH 2/2] drm/bridge: analogix: Enable EDP_BACKLIGHT_FREQ_PWM_PIN_PASSTHRU

From: Alexandru M Stan
Date: Thu Mar 15 2018 - 22:59:52 EST


Configure the DPCD registers for the backlight to respect the pwm frequency
of the input. We sometimes don't want it to generate its own.

Signed-off-by: Alexandru M Stan <amstan@xxxxxxxxxxxx>
---

drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 48 ++++++++++++++++++++++
drivers/gpu/drm/bridge/analogix/analogix_dp_core.h | 1 +
2 files changed, 49 insertions(+)

diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
index 5c52307146c7..b830403be8eb 100644
--- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
+++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
@@ -916,6 +916,46 @@ static irqreturn_t analogix_dp_irq_thread(int irq, void *arg)
return IRQ_HANDLED;
}

+static int analogix_dp_backlight_pwm_passthru(struct analogix_dp_device *dp)
+{
+ u8 value;
+ const u8 expected_cap = DP_EDP_BACKLIGHT_BRIGHTNESS_PWM_PIN_CAP |
+ DP_EDP_BACKLIGHT_FREQ_PWM_PIN_PASSTHRU_CAP;
+ int ret = 0;
+
+ ret = drm_dp_dpcd_readb(&dp->aux, DP_EDP_BACKLIGHT_ADJUSTMENT_CAP,
+ &value);
+ if (ret != 1) {
+ DRM_DEV_ERROR(dp->dev,
+ "backlight PWM passthru: Can't read BACKLIGHT_ADJUSTMENT_CAP\n");
+ return ret;
+ }
+
+ if ((value & expected_cap) != expected_cap) {
+ DRM_DEV_ERROR(dp->dev,
+ "panel doesn't support backlight PWM passthru, BACKLIGHT_ADJUSTMENT_CAP=0x%02x\n",
+ value);
+ return -1;
+ }
+
+ ret = drm_dp_dpcd_readb(&dp->aux, DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
+ &value);
+ if (ret != 1) {
+ DRM_DEV_ERROR(dp->dev,
+ "backlight PWM passthru: Can't read BACKLIGHT_MODE_SET_REGISTER\n");
+ return ret;
+ }
+
+ value |= DP_EDP_BACKLIGHT_FREQ_PWM_PIN_PASSTHRU_ENABLE;
+ ret = drm_dp_dpcd_writeb(&dp->aux, DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
+ value);
+ if (ret != 1) {
+ DRM_DEV_ERROR(dp->dev,
+ "backlight PWM passthru: Can't write BACKLIGHT_MODE_SET_REGISTER\n");
+ }
+ return ret;
+}
+
static void analogix_dp_commit(struct analogix_dp_device *dp)
{
int ret;
@@ -954,6 +994,12 @@ static void analogix_dp_commit(struct analogix_dp_device *dp)
dp->psr_enable = analogix_dp_detect_sink_psr(dp);
if (dp->psr_enable)
analogix_dp_enable_sink_psr(dp);
+
+ if (dp->backlight_pwm_passthru) {
+ if (analogix_dp_backlight_pwm_passthru(dp) != 1)
+ DRM_DEV_ERROR(dp->dev,
+ "Could not enable backlight pwm pin passthru.\n");
+ }
}

/*
@@ -1424,6 +1470,8 @@ analogix_dp_bind(struct device *dev, struct drm_device *drm_dev,
if (IS_ERR(dp->reg_base))
return ERR_CAST(dp->reg_base);

+ dp->backlight_pwm_passthru =
+ of_property_read_bool(dev->of_node, "backlight-pwm-passthru");
dp->force_hpd = of_property_read_bool(dev->of_node, "force-hpd");

dp->hpd_gpio = of_get_named_gpio(dev->of_node, "hpd-gpios", 0);
diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.h b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.h
index 6a96ef7e6934..aea51413e78e 100644
--- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.h
+++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.h
@@ -171,6 +171,7 @@ struct analogix_dp_device {
struct phy *phy;
int dpms_mode;
int hpd_gpio;
+ bool backlight_pwm_passthru;
bool force_hpd;
bool psr_enable;
bool fast_train_support;
--
2.13.5