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From: Nathan Schulte <nmschulte@gmail.com>
To: intel-gfx@lists.freedesktop.org
Subject: [PATCH 1/2] [i915] add module param "force_dp_sst"
Date: Thu, 10 Mar 2016 17:43:23 -0600	[thread overview]
Message-ID: <1457653404-19950-2-git-send-email-nmschulte@gmail.com> (raw)
In-Reply-To: <1457653404-19950-1-git-send-email-nmschulte@gmail.com>

Adds an (unsafe; auto-kernel-tainting) boolean module parameter to the i915
drm driver: "force_dp_sst", which is disabled by default.  Enabling the
parameter forces newly connected DisplayPort sinks to report as not
supporting multi-stream transport (MST), thus "forcing" the use of
single-stream transport (SST).
---
 drivers/gpu/drm/i915/i915_drv.h    | 1 +
 drivers/gpu/drm/i915/i915_params.c | 5 +++++
 drivers/gpu/drm/i915/intel_dp.c    | 3 +++
 3 files changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index b0847b9..515e335 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2701,6 +2701,7 @@ struct i915_params {
 	int guc_log_level;
 	int use_mmio_flip;
 	int mmio_debug;
+	bool force_dp_sst;
 	bool verbose_state_checks;
 	bool nuclear_pageflip;
 	int edp_vswing;
diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
index 835d609..cc2aaf3 100644
--- a/drivers/gpu/drm/i915/i915_params.c
+++ b/drivers/gpu/drm/i915/i915_params.c
@@ -51,6 +51,7 @@ struct i915_params i915 __read_mostly = {
 	.disable_vtd_wa = 0,
 	.use_mmio_flip = 0,
 	.mmio_debug = 0,
+	.force_dp_sst = false,
 	.verbose_state_checks = 1,
 	.nuclear_pageflip = 0,
 	.edp_vswing = 0,
@@ -181,6 +182,10 @@ MODULE_PARM_DESC(mmio_debug,
 	"Enable the MMIO debug code for the first N failures (default: off). "
 	"This may negatively affect performance.");
 
+module_param_named_unsafe(force_dp_sst, i915.force_dp_sst, bool, 0600);
+MODULE_PARM_DESC(force_dp_sst,
+	"Force single-stream transport (SST; disable MST) for new DisplayPort sinks (default: false). ");
+
 module_param_named(verbose_state_checks, i915.verbose_state_checks, bool, 0600);
 MODULE_PARM_DESC(verbose_state_checks,
 	"Enable verbose logs (ie. WARN_ON()) in case of unexpected hw state conditions.");
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 1d8de43..4c4725e 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -3969,6 +3969,9 @@ intel_dp_probe_mst(struct intel_dp *intel_dp)
 {
 	u8 buf[1];
 
+	if (i915.force_dp_sst)
+		return false;
+
 	if (!intel_dp->can_mst)
 		return false;
 
-- 
2.7.0

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  reply	other threads:[~2016-03-10 23:43 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-10 23:43 i915: allow forcing SST on DisplayPort connectors Nathan Schulte
2016-03-10 23:43 ` Nathan Schulte [this message]
2016-03-11 13:45   ` [PATCH 1/2] [i915] add module param "force_dp_sst" Jani Nikula
2016-03-10 23:43 ` [PATCH 2/2] [i915] move bools to end of i915_params struct Nathan Schulte
2016-03-11  7:40 ` ✗ Fi.CI.BAT: failure for series starting with [1/2,i915] add module param "force_dp_sst" Patchwork
2016-03-11  8:47   ` Joonas Lahtinen
2016-03-14 16:36 ` [PATCH v2] i915: module param to disable DisplayPort MST Nathan Schulte
2016-03-14 16:36   ` [PATCH] [i915] add module param "enable_dp_mst" Nathan Schulte
2016-03-15  8:43     ` Daniel Vetter
2016-03-15 15:14   ` [PATCH v3] drm/i915: " Nathan Schulte
2016-03-16 15:40     ` Daniel Vetter

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