[PATCH 18/19] drm/i915: save some time when waiting the eDP timings

Paulo Zanoni
2013-11-21T15:48:18Z

From: Paulo Zanoni <paulo.r.zanoni@intel.com>

The eDP spec defines some points where after you do action A, you have
to wait some time before action B. The thing is that in our driver
action B does not happen exactly after action A, but we still use
msleep() calls directly. What this patch happens is that we record the
timestamp of when action A happened, then, just before action B, we
look at how much time has passed and only sleep the remaining amount
needed.

With this change, I am able to save about 5-20ms (out of the total
200ms) of the backlight_off delay and completely skip the 1ms
backlight_on delay. The 600ms vdd_off delay doesn't happen during
normal usage anymore due to a previous patch.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
---
drivers/gpu/drm/i915/intel_dp.c | 38 +++++++++++++++++++++++++++++++++++---
drivers/gpu/drm/i915/intel_drv.h | 3 +++
2 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index b438e76..3a1ca80 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1051,12 +1051,41 @@ static void ironlake_wait_panel_off(struct intel_dp *intel_dp)
ironlake_wait_panel_status(intel_dp, IDLE_OFF_MASK, IDLE_OFF_VALUE);
}

+static void ironlake_wait_jiffies_delay(unsigned long timestamp,
+ int to_wait_ms)
+{
+ unsigned long target = timestamp + msecs_to_jiffies(to_wait_ms);
+ unsigned long diff;
+
+ if (time_after(target, jiffies)) {
+ diff = (long)target - (long)jiffies;
+ msleep(diff);
+ }
+}
+
static void ironlake_wait_panel_power_cycle(struct intel_dp *intel_dp)
{
DRM_DEBUG_KMS("Wait for panel power cycle\n");
+
+ /* When we disable the VDD override bit last we have to do the manual
+ * wait. */
+ ironlake_wait_jiffies_delay(intel_dp->last_power_cycle,
+ intel_dp->panel_power_cycle_delay);
+
ironlake_wait_panel_status(intel_dp, IDLE_CYCLE_MASK, IDLE_CYCLE_VALUE);
}

+static void ironlake_wait_backlight_on(struct intel_dp *intel_dp)
+{
+ ironlake_wait_jiffies_delay(intel_dp->last_power_on,
+ intel_dp->backlight_on_delay);
+}
+
+static void ironlake_edp_wait_backlight_off(struct intel_dp *intel_dp)
+{
+ ironlake_wait_jiffies_delay(intel_dp->last_backlight_off,
+ intel_dp->backlight_off_delay);
+}

/* Read the current pp_control value, unlocking the register if it
* is locked
@@ -1144,7 +1173,7 @@ static void ironlake_panel_vdd_off_sync(struct intel_dp *intel_dp)
I915_READ(pp_stat_reg), I915_READ(pp_ctrl_reg));

if ((pp & POWER_TARGET_ON) == 0)
- msleep(intel_dp->panel_power_cycle_delay);
+ intel_dp->last_power_cycle = jiffies;

intel_runtime_pm_put(dev_priv);
}
@@ -1219,6 +1248,7 @@ void ironlake_edp_panel_on(struct intel_dp *intel_dp)
POSTING_READ(pp_ctrl_reg);

ironlake_wait_panel_on(intel_dp);
+ intel_dp->last_power_on = jiffies;

if (IS_GEN5(dev)) {
pp |= PANEL_POWER_RESET; /* restore panel reset bit */
@@ -1239,6 +1269,8 @@ void ironlake_edp_panel_off(struct intel_dp *intel_dp)

DRM_DEBUG_KMS("Turn eDP power off\n");

+ ironlake_edp_wait_backlight_off(intel_dp);
+
pp = ironlake_get_pp_control(intel_dp);
/* We need to switch off panel power _and_ force vdd, for otherwise some
* panels get very unhappy and cease to work. */
@@ -1270,7 +1302,7 @@ void ironlake_edp_backlight_on(struct intel_dp *intel_dp)
* link. So delay a bit to make sure the image is solid before
* allowing it to appear.
*/
- msleep(intel_dp->backlight_on_delay);
+ ironlake_wait_backlight_on(intel_dp);
pp = ironlake_get_pp_control(intel_dp);
pp |= EDP_BLC_ENABLE;

@@ -1302,7 +1334,7 @@ void ironlake_edp_backlight_off(struct intel_dp *intel_dp)

I915_WRITE(pp_ctrl_reg, pp);
POSTING_READ(pp_ctrl_reg);
- msleep(intel_dp->backlight_off_delay);
+ intel_dp->last_backlight_off = jiffies;
}

static void ironlake_edp_pll_on(struct intel_dp *intel_dp)
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 5596498..778a7be 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -484,6 +484,9 @@ struct intel_dp {
int backlight_off_delay;
struct delayed_work panel_vdd_work;
bool want_panel_vdd;
+ unsigned long last_power_cycle;
+ unsigned long last_power_on;
+ unsigned long last_backlight_off;
bool psr_setup_done;
struct intel_connector *attached_connector;
};
--
1.8.3.1