[Intel-gfx] [PATCH v3] drm/i915/psr: Lockless version of psr_wait_for_idle

[Shaikh, Azhar]

>-----Original Message-----
>From: Intel-gfx [mailto:intel-gfx-bounces at lists.freedesktop.org] On Behalf Of
>Tarun Vyas
>Sent: Friday, June 22, 2018 1:59 AM
>To: intel-gfx at lists.freedesktop.org
>Cc: Pandiyan, Dhinakaran <dhinakaran.pandiyan at intel.com>; Vivi, Rodrigo
><rodrigo.vivi at intel.com>
>Subject: [Intel-gfx] [PATCH v3] drm/i915/psr: Lockless version of
>psr_wait_for_idle
>
>This is a lockless version of the exisiting psr_wait_for_idle().
>We want to wait for PSR to idle out inside intel_pipe_update_start.
>At the time of a pipe update, we should never race with any psr enable or
>disable code, which is a part of crtc enable/disable. So, we can live w/o taking
>any psr locks at all.
>The follow up patch will use this lockless wait inside pipe_update_ start to
>wait for PSR to idle out before checking for vblank evasion.
>
>Even if psr is never enabled, psr2_enabled will be false and this function will
>wait for PSR1 to idle out, which should just return immediately, so a very short
>(~1-2 usec) wait for cases where PSR is disabled.
>
>v2: Add comment to explain the 25msec timeout (DK)
>
>v3: Rename psr_wait_for_idle to __psr_wait_for_idle_locked to avoid
>    naming conflicts and propagate err (if any) to the caller (Chris)
>
>Signed-off-by: Tarun Vyas <tarun.vyas at intel.com>
>---
> drivers/gpu/drm/i915/intel_drv.h |  1 +  drivers/gpu/drm/i915/intel_psr.c |
>25 +++++++++++++++++++++++--
> 2 files changed, 24 insertions(+), 2 deletions(-)
>
>diff --git a/drivers/gpu/drm/i915/intel_drv.h
>b/drivers/gpu/drm/i915/intel_drv.h
>index 578346b8d7e2..9cb2b8afdd3e 100644
>--- a/drivers/gpu/drm/i915/intel_drv.h
>+++ b/drivers/gpu/drm/i915/intel_drv.h
>@@ -1920,6 +1920,7 @@ void intel_psr_compute_config(struct intel_dp
>*intel_dp,
> 			      struct intel_crtc_state *crtc_state);  void
>intel_psr_irq_control(struct drm_i915_private *dev_priv, bool debug);  void
>intel_psr_irq_handler(struct drm_i915_private *dev_priv, u32 psr_iir);
>+int intel_psr_wait_for_idle(struct drm_i915_private *dev_priv);
>
> /* intel_runtime_pm.c */
> int intel_power_domains_init(struct drm_i915_private *); diff --git
>a/drivers/gpu/drm/i915/intel_psr.c b/drivers/gpu/drm/i915/intel_psr.c
>index aea81ace854b..41e6962923ae 100644
>--- a/drivers/gpu/drm/i915/intel_psr.c
>+++ b/drivers/gpu/drm/i915/intel_psr.c
>@@ -757,7 +757,28 @@ void intel_psr_disable(struct intel_dp *intel_dp,
> 	cancel_work_sync(&dev_priv->psr.work);
> }
>
>-static bool psr_wait_for_idle(struct drm_i915_private *dev_priv)
>+int intel_psr_wait_for_idle(struct drm_i915_private *dev_priv) {


I think you should upload this patch and https://patchwork.freedesktop.org/patch/231033/  as a series.
intel_psr_wait_for_idle_lockless() does not get called anywhere in this patch.

>+	i915_reg_t reg;
>+	u32 mask;
>+
>+	if (dev_priv->psr.psr2_enabled) {
>+		reg = EDP_PSR2_STATUS;
>+		mask = EDP_PSR2_STATUS_STATE_MASK;
>+	} else {
>+		reg = EDP_PSR_STATUS;
>+		mask = EDP_PSR_STATUS_STATE_MASK;
>+	}
>+
>+	/*
>+	 * The  25 msec timeout accounts for a frame @ 60Hz refresh rate,
>+	 * exit training an aux handshake time.
>+	 */
>+	return intel_wait_for_register(dev_priv, reg, mask,
>+				       EDP_PSR_STATUS_STATE_IDLE, 25); }
>+
>+static bool __psr_wait_for_idle_locked(struct drm_i915_private
>+*dev_priv)
> {
> 	struct intel_dp *intel_dp;
> 	i915_reg_t reg;
>@@ -803,7 +824,7 @@ static void intel_psr_work(struct work_struct *work)
> 	 * PSR might take some time to get fully disabled
> 	 * and be ready for re-enable.
> 	 */
>-	if (!psr_wait_for_idle(dev_priv))
>+	if (!__psr_wait_for_idle_locked(dev_priv))
> 		goto unlock;
>
> 	/*
>--
>2.13.5
>
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Regards,
Azhar Shaikh