Re: [PATCH] drm/i915: Detect USB-C specific dongles before reducing M and N

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On 05/11/2017 03:03 AM, Jani Nikula wrote:

On Wed, 10 May 2017, clinton.a.taylor@xxxxxxxxx wrote:

From: Clint Taylor <clinton.a.taylor@xxxxxxxxx>

The Analogix 7737 DP to HDMI converter requires reduced N and M values when
to operate correctly at HBR2. Detect this IC by its OUI value of 0x0022B9.

I'm not happy, but I also see no alternative than to go this
route. Thanks for the patch. I do think we need to start a common drm
quirk database for this stuff though. Added one, and rebased this one on
top:

https://patchwork.freedesktop.org/series/24282/

Please give it a go; I don't have a DA200.
patches work as expected. quirks is set correctly when OUI 0x0022B9 based DA200 and SlimPort USB-C dongles are used. All other dongles tested do not set quirks.
[ 64.569833] [drm:intel_dp_read_desc] DP branch: OUI 00-1c-f8 dev-ID 176GB0 HW-rev 1.0 SW-rev 7.38 quirks 0x0000
[ 111.053902] [drm:intel_dp_read_desc] DP branch: OUI 00-22-b9 dev-ID 7737 HW-rev 10.12 SW-rev 6.4 quirks 0x0001 

-Clint




BR,
Jani.


Cc: Jani Nikula <jani.nikula@xxxxxxxxx>
Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@xxxxxxxxx>

Signed-off-by: Clint Taylor <clinton.a.taylor@xxxxxxxxx>
---
  drivers/gpu/drm/i915/i915_drv.h      |  3 ++-
  drivers/gpu/drm/i915/intel_display.c | 22 ++++++++++++++--------
  drivers/gpu/drm/i915/intel_dp.c      | 22 ++++++++++++++++++++--
  drivers/gpu/drm/i915/intel_dp_mst.c  |  3 ++-
  drivers/gpu/drm/i915/intel_drv.h     |  1 +
  5 files changed, 39 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 74dffbe..492e47e 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -563,7 +563,8 @@ struct intel_link_m_n {
void intel_link_compute_m_n(int bpp, int nlanes, 
  			    int pixel_clock, int link_clock,
-			    struct intel_link_m_n *m_n);
+			    struct intel_link_m_n *m_n,
+				bool reduce_m_n);
/* Interface history: 
   *
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 7bcc604..8920a99 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -6104,7 +6104,7 @@ static int ironlake_fdi_compute_config(struct intel_crtc *intel_crtc,
  	pipe_config->fdi_lanes = lane;
intel_link_compute_m_n(pipe_config->pipe_bpp, lane, fdi_dotclock, 
-			       link_bw, &pipe_config->fdi_m_n);
+			       link_bw, &pipe_config->fdi_m_n, false);
ret = ironlake_check_fdi_lanes(dev, intel_crtc->pipe, pipe_config); 
  	if (ret == -EINVAL && pipe_config->pipe_bpp > 6*3) {
@@ -6280,7 +6280,8 @@ static int intel_crtc_compute_config(struct intel_crtc *crtc,
  }
static void compute_m_n(unsigned int m, unsigned int n, 
-			uint32_t *ret_m, uint32_t *ret_n)
+			uint32_t *ret_m, uint32_t *ret_n,
+			   bool reduce_m_n)
  {
  	/*
  	 * Reduce M/N as much as possible without loss in precision. Several DP
@@ -6288,9 +6289,11 @@ static void compute_m_n(unsigned int m, unsigned int n,
  	 * values. The passed in values are more likely to have the least
  	 * significant bits zero than M after rounding below, so do this first.
  	 */
-	while ((m & 1) == 0 && (n & 1) == 0) {
-		m >>= 1;
-		n >>= 1;
+	if (reduce_m_n) {
+		while ((m & 1) == 0 && (n & 1) == 0) {
+			m >>= 1;
+			n >>= 1;
+		}
  	}
*ret_n = min_t(unsigned int, roundup_pow_of_two(n), DATA_LINK_N_MAX); 
@@ -6301,16 +6304,19 @@ static void compute_m_n(unsigned int m, unsigned int n,
  void
  intel_link_compute_m_n(int bits_per_pixel, int nlanes,
  		       int pixel_clock, int link_clock,
-		       struct intel_link_m_n *m_n)
+		       struct intel_link_m_n *m_n,
+			  bool reduce_m_n)
  {
  	m_n->tu = 64;
compute_m_n(bits_per_pixel * pixel_clock, 
  		    link_clock * nlanes * 8,
-		    &m_n->gmch_m, &m_n->gmch_n);
+		    &m_n->gmch_m, &m_n->gmch_n,
+		    reduce_m_n);
compute_m_n(pixel_clock, link_clock, 
-		    &m_n->link_m, &m_n->link_n);
+		    &m_n->link_m, &m_n->link_n,
+		    reduce_m_n);
  }
static inline bool intel_panel_use_ssc(struct drm_i915_private *dev_priv) 
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 4a6feb6..f4c0582 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1548,6 +1548,20 @@ static void intel_dp_print_rates(struct intel_dp *intel_dp)
  	DRM_DEBUG_KMS("common rates: %s\n", str);
  }
+bool __intel_reduced_m_n(struct intel_dp *intel_dp) 
+{
+	struct intel_dp_desc *desc = &intel_dp->desc;
+	bool ret = false;
+
+	/* Analogix 7737 needs reduced N and M at HBR2 link rates */
+	if (desc->oui[0] == 0x00 &&
+	    desc->oui[1] == 0x22 &&
+	    desc->oui[2] == 0xb9)
+		ret = true;
+
+	return ret;
+}
+
  bool
  __intel_dp_read_desc(struct intel_dp *intel_dp, struct intel_dp_desc *desc)
  {
@@ -1568,6 +1582,8 @@ bool intel_dp_read_desc(struct intel_dp *intel_dp)
  	if (!__intel_dp_read_desc(intel_dp, desc))
  		return false;
+ intel_dp->reduce_m_n = __intel_reduced_m_n(intel_dp); 
+
  	dev_id_len = strnlen(desc->device_id, sizeof(desc->device_id));
  	DRM_DEBUG_KMS("DP %s: OUI %*phD%s dev-ID %*pE HW-rev %d.%d SW-rev %d.%d\n",
  		      drm_dp_is_branch(intel_dp->dpcd) ? "branch" : "sink",
@@ -1790,7 +1806,8 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
  	intel_link_compute_m_n(bpp, lane_count,
  			       adjusted_mode->crtc_clock,
  			       pipe_config->port_clock,
-			       &pipe_config->dp_m_n);
+			       &pipe_config->dp_m_n,
+				intel_dp->reduce_m_n);
if (intel_connector->panel.downclock_mode != NULL && 
  		dev_priv->drrs.type == SEAMLESS_DRRS_SUPPORT) {
@@ -1798,7 +1815,8 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
  			intel_link_compute_m_n(bpp, lane_count,
  				intel_connector->panel.downclock_mode->clock,
  				pipe_config->port_clock,
-				&pipe_config->dp_m2_n2);
+				&pipe_config->dp_m2_n2,
+				intel_dp->reduce_m_n);
  	}
/* 
diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
index 68c788e..81fd8dc 100644
--- a/drivers/gpu/drm/i915/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/intel_dp_mst.c
@@ -79,7 +79,8 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
  	intel_link_compute_m_n(bpp, lane_count,
  			       adjusted_mode->crtc_clock,
  			       pipe_config->port_clock,
-			       &pipe_config->dp_m_n);
+			       &pipe_config->dp_m_n,
+				intel_dp->reduce_m_n);
pipe_config->dp_m_n.tu = slots; diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h 
index e8de2f67..50e5077 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1057,6 +1057,7 @@ struct intel_dp {
/* Displayport compliance testing */ 
  	struct intel_dp_compliance compliance;
+	bool reduce_m_n;
  };
struct intel_lspcon { 

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