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drm/i915: panel: Use atomic PWM API for devs with an external PWM con…
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…troller

Now that the PWM drivers which we use have been converted to the atomic
PWM API, we can move the i915 panel code over to using the atomic PWM API.

The removes a long standing FIXME and this removes a flicker where
the backlight brightness would jump to 100% when i915 loads even if
using the fastset path.

Note that this commit also simplifies pwm_disable_backlight(), by dropping
the intel_panel_actually_set_backlight(..., 0) call. This call sets the
PWM to 0% duty-cycle. I believe that this call was only present as a
workaround for a bug in the pwm-crc.c driver where it failed to clear the
PWM_OUTPUT_ENABLE bit. This is fixed by an earlier patch in this series.

After the dropping of this workaround, the usleep call, which seems
unnecessary to begin with, has no useful effect anymore, so drop that too.

Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
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@jwrdegoede @intel-lab-lkp
jwrdegoede authored and intel-lab-lkp committed Aug 24, 2020
1 parent 2672f33 commit 72f1809
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Showing 2 changed files with 33 additions and 40 deletions.
3 changes: 2 additions & 1 deletion drivers/gpu/drm/i915/display/intel_display_types.h
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,7 @@

#include <linux/async.h>
#include <linux/i2c.h>
#include <linux/pwm.h>
#include <linux/sched/clock.h>

#include <drm/drm_atomic.h>
Expand Down Expand Up @@ -223,7 +224,7 @@ struct intel_panel {
bool util_pin_active_low; /* bxt+ */
u8 controller; /* bxt+ only */
struct pwm_device *pwm;
int pwm_period_ns;
struct pwm_state pwm_state;

/* DPCD backlight */
u8 pwmgen_bit_count;
Expand Down
70 changes: 31 additions & 39 deletions drivers/gpu/drm/i915/display/intel_panel.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -592,10 +592,10 @@ static u32 bxt_get_backlight(struct intel_connector *connector)
static u32 pwm_get_backlight(struct intel_connector *connector)
{
struct intel_panel *panel = &connector->panel;
int duty_ns;
struct pwm_state state;

duty_ns = pwm_get_duty_cycle(panel->backlight.pwm);
return DIV_ROUND_UP(duty_ns * 100, panel->backlight.pwm_period_ns);
pwm_get_state(panel->backlight.pwm, &state);
return pwm_get_relative_duty_cycle(&state, 100);
}

static void lpt_set_backlight(const struct drm_connector_state *conn_state, u32 level)
Expand Down Expand Up @@ -669,10 +669,9 @@ static void bxt_set_backlight(const struct drm_connector_state *conn_state, u32
static void pwm_set_backlight(const struct drm_connector_state *conn_state, u32 level)
{
struct intel_panel *panel = &to_intel_connector(conn_state->connector)->panel;
int duty_ns = DIV_ROUND_UP(level * panel->backlight.pwm_period_ns, 100);

pwm_config(panel->backlight.pwm, duty_ns,
panel->backlight.pwm_period_ns);
pwm_set_relative_duty_cycle(&panel->backlight.pwm_state, level, 100);
pwm_apply_state(panel->backlight.pwm, &panel->backlight.pwm_state);
}

static void
Expand Down Expand Up @@ -841,10 +840,8 @@ static void pwm_disable_backlight(const struct drm_connector_state *old_conn_sta
struct intel_connector *connector = to_intel_connector(old_conn_state->connector);
struct intel_panel *panel = &connector->panel;

/* Disable the backlight */
intel_panel_actually_set_backlight(old_conn_state, 0);
usleep_range(2000, 3000);
pwm_disable(panel->backlight.pwm);
panel->backlight.pwm_state.enabled = false;
pwm_apply_state(panel->backlight.pwm, &panel->backlight.pwm_state);
}

void intel_panel_disable_backlight(const struct drm_connector_state *old_conn_state)
Expand Down Expand Up @@ -1176,9 +1173,12 @@ static void pwm_enable_backlight(const struct intel_crtc_state *crtc_state,
{
struct intel_connector *connector = to_intel_connector(conn_state->connector);
struct intel_panel *panel = &connector->panel;
int level = panel->backlight.level;

pwm_enable(panel->backlight.pwm);
intel_panel_actually_set_backlight(conn_state, panel->backlight.level);
level = intel_panel_compute_brightness(connector, level);
pwm_set_relative_duty_cycle(&panel->backlight.pwm_state, level, 100);
panel->backlight.pwm_state.enabled = true;
pwm_apply_state(panel->backlight.pwm, &panel->backlight.pwm_state);
}

static void __intel_panel_enable_backlight(const struct intel_crtc_state *crtc_state,
Expand Down Expand Up @@ -1897,8 +1897,7 @@ static int pwm_setup_backlight(struct intel_connector *connector,
struct drm_i915_private *dev_priv = to_i915(dev);
struct intel_panel *panel = &connector->panel;
const char *desc;
u32 level, ns;
int retval;
u32 level;

/* Get the right PWM chip for DSI backlight according to VBT */
if (dev_priv->vbt.dsi.config->pwm_blc == PPS_BLC_PMIC) {
Expand All @@ -1916,35 +1915,28 @@ static int pwm_setup_backlight(struct intel_connector *connector,
return -ENODEV;
}

panel->backlight.pwm_period_ns = NSEC_PER_SEC /
get_vbt_pwm_freq(dev_priv);

/*
* FIXME: pwm_apply_args() should be removed when switching to
* the atomic PWM API.
*/
pwm_apply_args(panel->backlight.pwm);

panel->backlight.max = 100; /* 100% */
panel->backlight.min = get_backlight_min_vbt(connector);
level = intel_panel_compute_brightness(connector, 100);
ns = DIV_ROUND_UP(level * panel->backlight.pwm_period_ns, 100);

retval = pwm_config(panel->backlight.pwm, ns,
panel->backlight.pwm_period_ns);
if (retval < 0) {
drm_err(&dev_priv->drm, "Failed to configure the pwm chip\n");
pwm_put(panel->backlight.pwm);
panel->backlight.pwm = NULL;
return retval;
}
if (pwm_is_enabled(panel->backlight.pwm)) {
/* PWM is already enabled, use existing settings */
pwm_get_state(panel->backlight.pwm, &panel->backlight.pwm_state);

level = DIV_ROUND_UP_ULL(pwm_get_duty_cycle(panel->backlight.pwm) * 100,
panel->backlight.pwm_period_ns);
level = intel_panel_compute_brightness(connector, level);
panel->backlight.level = clamp(level, panel->backlight.min,
panel->backlight.max);
panel->backlight.enabled = panel->backlight.level != 0;
level = pwm_get_relative_duty_cycle(&panel->backlight.pwm_state,
100);
level = intel_panel_compute_brightness(connector, level);
panel->backlight.level = clamp(level, panel->backlight.min,
panel->backlight.max);
panel->backlight.enabled = true;

drm_dbg_kms(&dev_priv->drm, "PWM already enabled at freq %lld, VBT freq %d, level %d\n",
NSEC_PER_SEC / panel->backlight.pwm_state.period,
get_vbt_pwm_freq(dev_priv), level);
} else {
/* Set period from VBT frequency, leave other settings at 0. */
panel->backlight.pwm_state.period =
NSEC_PER_SEC / get_vbt_pwm_freq(dev_priv);
}

drm_info(&dev_priv->drm, "Using %s PWM for LCD backlight control\n",
desc);
Expand Down

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