62 lines
2.1 KiB
Diff
62 lines
2.1 KiB
Diff
From f99a0874dccc1ba9f9ead4473ba09603d10946b4 Mon Sep 17 00:00:00 2001
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From: Mike Galbraith <umgwanakikbuti@gmail.com>
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Date: Sat, 27 Feb 2016 08:09:11 +0100
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Subject: [PATCH 23/62] drm/i915: Use preempt_disable/enable_rt() where
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recommended
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Mario Kleiner suggest in commit
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ad3543ede630f ("drm/intel: Push get_scanout_position() timestamping into kms driver.")
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a spots where preemption should be disabled on PREEMPT_RT. The
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difference is that on PREEMPT_RT the intel_uncore::lock disables neither
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preemption nor interrupts and so region remains preemptible.
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The area covers only register reads and writes. The part that worries me
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is:
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- __intel_get_crtc_scanline() the worst case is 100us if no match is
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found.
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- intel_crtc_scanlines_since_frame_timestamp() not sure how long this
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may take in the worst case.
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It was in the RT queue for a while and nobody complained.
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Disable preemption on PREEPMPT_RT during timestamping.
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[bigeasy: patch description.]
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Cc: Mario Kleiner <mario.kleiner.de@gmail.com>
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Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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drivers/gpu/drm/i915/i915_irq.c | 6 ++++--
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1 file changed, 4 insertions(+), 2 deletions(-)
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diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
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index f93ffa6626a5..6e9d033cf808 100644
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--- a/drivers/gpu/drm/i915/i915_irq.c
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+++ b/drivers/gpu/drm/i915/i915_irq.c
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@@ -917,7 +917,8 @@ static bool i915_get_crtc_scanoutpos(struct drm_crtc *_crtc,
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*/
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spin_lock_irqsave(&dev_priv->uncore.lock, irqflags);
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- /* preempt_disable_rt() should go right here in PREEMPT_RT patchset. */
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+ if (IS_ENABLED(CONFIG_PREEMPT_RT))
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+ preempt_disable();
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/* Get optional system timestamp before query. */
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if (stime)
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@@ -981,7 +982,8 @@ static bool i915_get_crtc_scanoutpos(struct drm_crtc *_crtc,
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if (etime)
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*etime = ktime_get();
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- /* preempt_enable_rt() should go right here in PREEMPT_RT patchset. */
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+ if (IS_ENABLED(CONFIG_PREEMPT_RT))
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+ preempt_enable();
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spin_unlock_irqrestore(&dev_priv->uncore.lock, irqflags);
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--
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2.43.0
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