[Intel-gfx] [PATCH 2/3] drm/i915: Instrument PSR parameter for possible quirks with link standby.

[Rodrigo Vivi]

Link standby support has been deprecated with 'commit 89251b177
("drm/i915: PSR: deprecate link_standby support for core platforms.")'

The reason for that is that main link in full off offers more power
savings and some platforms implementations on source side had known
bugs with link standby.

However we don't know all panels out there and we don't fully rely
on the VBT information after the case found with the commit that
made us to deprecate link standby.

So, before enable PSR by default let's instrument the PSR parameter
in a way that we can identify different panels out there that might
require or work better with link standby mode.

It is also useful to say that for backward compatibility I'm not
changing the meaning of this flag. So "0" still means disabled
and "1" means enabled with full support and maximum power savings.

Negative values are being used for debug purposes since I'd like
to save positive number for future use like PSR2 for instance.

Cc: Paulo Zanoni <paulo.r.zanoni at intel.com>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
---
 drivers/gpu/drm/i915/i915_debugfs.c |  5 +++++
 drivers/gpu/drm/i915/i915_drv.h     |  1 +
 drivers/gpu/drm/i915/i915_params.c  |  7 ++++++-
 drivers/gpu/drm/i915/intel_psr.c    | 13 ++++++++++++-
 4 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 24318b7..efe973b 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -2567,6 +2567,10 @@ static int i915_edp_psr_status(struct seq_file *m, void *data)
 				enabled = true;
 		}
 	}
+
+	seq_printf(m, "Forcing main link standby: %s\n",
+		   yesno(dev_priv->psr.link_standby));
+
 	seq_printf(m, "HW Enabled & Active bit: %s", yesno(enabled));
 
 	if (!HAS_DDI(dev))
@@ -2587,6 +2591,7 @@ static int i915_edp_psr_status(struct seq_file *m, void *data)
 
 		seq_printf(m, "Performance_Counter: %u\n", psrperf);
 	}
+
 	mutex_unlock(&dev_priv->psr.lock);
 
 	intel_runtime_pm_put(dev_priv);
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 5edd393..de086f0 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -969,6 +969,7 @@ struct i915_psr {
 	unsigned busy_frontbuffer_bits;
 	bool psr2_support;
 	bool aux_frame_sync;
+	bool link_standby;
 };
 
 enum intel_pch {
diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
index 835d609..def8802 100644
--- a/drivers/gpu/drm/i915/i915_params.c
+++ b/drivers/gpu/drm/i915/i915_params.c
@@ -126,7 +126,12 @@ MODULE_PARM_DESC(enable_execlists,
 	"(-1=auto [default], 0=disabled, 1=enabled)");
 
 module_param_named_unsafe(enable_psr, i915.enable_psr, int, 0600);
-MODULE_PARM_DESC(enable_psr, "Enable PSR (default: false)");
+MODULE_PARM_DESC(enable_psr, "Enable PSR "
+		 "(-1=force link standby for debug, 0=disabled [default], 1=enabled)"
+		 "In case you needed to force debug mode, please "
+		 "report PCI device ID, subsystem vendor and subsystem device ID "
+		 "to intel-gfx at lists.freedesktop.org, if your machine needs it. "
+		 "It will then be included in an upcoming module version.");
 
 module_param_named_unsafe(preliminary_hw_support, i915.preliminary_hw_support, int, 0600);
 MODULE_PARM_DESC(preliminary_hw_support,
diff --git a/drivers/gpu/drm/i915/intel_psr.c b/drivers/gpu/drm/i915/intel_psr.c
index 9ccff30..7529f93 100644
--- a/drivers/gpu/drm/i915/intel_psr.c
+++ b/drivers/gpu/drm/i915/intel_psr.c
@@ -225,7 +225,12 @@ static void hsw_psr_enable_sink(struct intel_dp *intel_dp)
 		   (aux_clock_divider << DP_AUX_CH_CTL_BIT_CLOCK_2X_SHIFT));
 	}
 
-	drm_dp_dpcd_writeb(&intel_dp->aux, DP_PSR_EN_CFG, DP_PSR_ENABLE);
+	if (dev_priv->psr.link_standby)
+		drm_dp_dpcd_writeb(&intel_dp->aux, DP_PSR_EN_CFG,
+				   DP_PSR_ENABLE | DP_PSR_MAIN_LINK_ACTIVE);
+	else
+		drm_dp_dpcd_writeb(&intel_dp->aux, DP_PSR_EN_CFG,
+				   DP_PSR_ENABLE);
 }
 
 static void vlv_psr_enable_source(struct intel_dp *intel_dp)
@@ -280,6 +285,9 @@ static void hsw_psr_enable_source(struct intel_dp *intel_dp)
 	if (IS_HASWELL(dev))
 		val |= EDP_PSR_MIN_LINK_ENTRY_TIME_8_LINES;
 
+	if (dev_priv->psr.link_standby)
+		val |= EDP_PSR_LINK_STANDBY;
+
 	I915_WRITE(EDP_PSR_CTL, val |
 		   max_sleep_time << EDP_PSR_MAX_SLEEP_TIME_SHIFT |
 		   idle_frames << EDP_PSR_IDLE_FRAME_SHIFT |
@@ -763,6 +771,9 @@ void intel_psr_init(struct drm_device *dev)
 	dev_priv->psr_mmio_base = IS_HASWELL(dev_priv) ?
 		HSW_EDP_PSR_BASE : BDW_EDP_PSR_BASE;
 
+	if (i915.enable_psr == -1)
+		dev_priv->psr.link_standby = true;
+
 	INIT_DELAYED_WORK(&dev_priv->psr.work, intel_psr_work);
 	mutex_init(&dev_priv->psr.lock);
 }
-- 
2.4.3