drm/i915: relax uncritical udelay_range() settings

udelay_range(2, 3) is inefficient and as discussions with Jani Nikula
<jani.nikula@linux.intel.com> unnecessary here. This replaces this
tight setting with a relaxed delay of min=20 and max=50. which helps
the hrtimer subsystem optimize timer handling.

Link: http://lkml.org/lkml/2016/12/15/127
Fixes: commit 37ab0810c9b7 ("drm/i915/bxt: DSI enable for BXT")
Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1481853560-19795-1-git-send-email-hofrat@osadl.org

diff --git a/drivers/gpu/drm/i915/intel_dsi.c b/drivers/gpu/drm/i915/intel_dsi.c
index 0668bbec50289fdd68d483fe8f9a991c49d781a6..c978852904edf00e770f89d76848118ce9f149fc 100644 (file)
--- a/drivers/gpu/drm/i915/intel_dsi.c
+++ b/drivers/gpu/drm/i915/intel_dsi.c
@@ -379,7 +379,8 @@ static void bxt_dsi_device_ready(struct intel_encoder *encoder)
                val &= ~ULPS_STATE_MASK;
                val |= (ULPS_STATE_ENTER | DEVICE_READY);
                I915_WRITE(MIPI_DEVICE_READY(port), val);
-               usleep_range(2, 3);
+               /* at least 2us - relaxed for hrtimer subsystem optimization */
+               usleep_range(10, 50);
 
                /* 3. Exit ULPS */
                val = I915_READ(MIPI_DEVICE_READY(port));