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

Chris Wilson
2013-11-21T16:00:28Z

On Thu, Nov 21, 2013 at 01:47:32PM -0200, Paulo Zanoni wrote:
> 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)
This is not hw specific, so just
intel_wait_until_after(timestamp_jiffies, 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);

msleep() expects a duration in ms, diff is in jiffies.
-Chris

--
Chris Wilson, Intel Open Source Technology Centre