Merge tag 'drm-dp-quirk-for-v4.12-rc4' of git://people.freedesktop.org/~airlied/linux

Pull drm displayport quirk support:
 "DP quirk for usb c dongles.

  As mentioned I have a separate request for fixing a regression, but
  also keeping the broken hw working, for certain USB-C DP adapters they
  require a minimised n/m parameters, but an attempt to do this
  generically has failed, we need to quirk these specific adapters.
  However doing it generically regressed some eDP panels.

  This pull adds the infrastructure and a quirk for the adapter"

* tag 'drm-dp-quirk-for-v4.12-rc4' of git://people.freedesktop.org/~airlied/linux:
  drm/i915: Detect USB-C specific dongles before reducing M and N
  drm/dp: start a DPCD based DP sink/branch device quirk database
  drm/i915: use drm DP helper to read DPCD desc
  drm/dp: add helper for reading DP sink/branch device desc from DPCD

8 files changed, 166 insertions, 58 deletions

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 3e5f52110ea1..213fb837e1c4 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -1208,3 +1208,86 @@ int drm_dp_stop_crc(struct drm_dp_aux *aux)
 	return 0;
 }
 EXPORT_SYMBOL(drm_dp_stop_crc);
+
+struct dpcd_quirk {
+	u8 oui[3];
+	bool is_branch;
+	u32 quirks;
+};
+
+#define OUI(first, second, third) { (first), (second), (third) }
+
+static const struct dpcd_quirk dpcd_quirk_list[] = {
+	/* Analogix 7737 needs reduced M and N at HBR2 link rates */
+	{ OUI(0x00, 0x22, 0xb9), true, BIT(DP_DPCD_QUIRK_LIMITED_M_N) },
+};
+
+#undef OUI
+
+/*
+ * Get a bit mask of DPCD quirks for the sink/branch device identified by
+ * ident. The quirk data is shared but it's up to the drivers to act on the
+ * data.
+ *
+ * For now, only the OUI (first three bytes) is used, but this may be extended
+ * to device identification string and hardware/firmware revisions later.
+ */
+static u32
+drm_dp_get_quirks(const struct drm_dp_dpcd_ident *ident, bool is_branch)
+{
+	const struct dpcd_quirk *quirk;
+	u32 quirks = 0;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(dpcd_quirk_list); i++) {
+		quirk = &dpcd_quirk_list[i];
+
+		if (quirk->is_branch != is_branch)
+			continue;
+
+		if (memcmp(quirk->oui, ident->oui, sizeof(ident->oui)) != 0)
+			continue;
+
+		quirks |= quirk->quirks;
+	}
+
+	return quirks;
+}
+
+/**
+ * drm_dp_read_desc - read sink/branch descriptor from DPCD
+ * @aux: DisplayPort AUX channel
+ * @desc: Device decriptor to fill from DPCD
+ * @is_branch: true for branch devices, false for sink devices
+ *
+ * Read DPCD 0x400 (sink) or 0x500 (branch) into @desc. Also debug log the
+ * identification.
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+int drm_dp_read_desc(struct drm_dp_aux *aux, struct drm_dp_desc *desc,
+		     bool is_branch)
+{
+	struct drm_dp_dpcd_ident *ident = &desc->ident;
+	unsigned int offset = is_branch ? DP_BRANCH_OUI : DP_SINK_OUI;
+	int ret, dev_id_len;
+
+	ret = drm_dp_dpcd_read(aux, offset, ident, sizeof(*ident));
+	if (ret < 0)
+		return ret;
+
+	desc->quirks = drm_dp_get_quirks(ident, is_branch);
+
+	dev_id_len = strnlen(ident->device_id, sizeof(ident->device_id));
+
+	DRM_DEBUG_KMS("DP %s: OUI %*phD dev-ID %*pE HW-rev %d.%d SW-rev %d.%d quirks 0x%04x\n",
+		      is_branch ? "branch" : "sink",
+		      (int)sizeof(ident->oui), ident->oui,
+		      dev_id_len, ident->device_id,
+		      ident->hw_rev >> 4, ident->hw_rev & 0xf,
+		      ident->sw_major_rev, ident->sw_minor_rev,
+		      desc->quirks);
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_dp_read_desc);
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index c9b0949f6c1a..963f6d4481f7 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -562,7 +562,8 @@ 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 3617927af269..3cabe52a4e3b 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -6101,7 +6101,7 @@ retry:
 	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) {
@@ -6277,7 +6277,8 @@ intel_reduce_m_n_ratio(uint32_t *num, uint32_t *den)
 }
 
 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
@@ -6285,9 +6286,11 @@ 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);
@@ -6298,16 +6301,19 @@ 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 ee77b519835c..fc691b8b317c 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1507,37 +1507,6 @@ static void intel_dp_print_rates(struct intel_dp *intel_dp)
 	DRM_DEBUG_KMS("common rates: %s\n", str);
 }
 
-bool
-__intel_dp_read_desc(struct intel_dp *intel_dp, struct intel_dp_desc *desc)
-{
-	u32 base = drm_dp_is_branch(intel_dp->dpcd) ? DP_BRANCH_OUI :
-						      DP_SINK_OUI;
-
-	return drm_dp_dpcd_read(&intel_dp->aux, base, desc, sizeof(*desc)) ==
-	       sizeof(*desc);
-}
-
-bool intel_dp_read_desc(struct intel_dp *intel_dp)
-{
-	struct intel_dp_desc *desc = &intel_dp->desc;
-	bool oui_sup = intel_dp->dpcd[DP_DOWN_STREAM_PORT_COUNT] &
-		       DP_OUI_SUPPORT;
-	int dev_id_len;
-
-	if (!__intel_dp_read_desc(intel_dp, desc))
-		return false;
-
-	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",
-		      (int)sizeof(desc->oui), desc->oui, oui_sup ? "" : "(NS)",
-		      dev_id_len, desc->device_id,
-		      desc->hw_rev >> 4, desc->hw_rev & 0xf,
-		      desc->sw_major_rev, desc->sw_minor_rev);
-
-	return true;
-}
-
 static int rate_to_index(int find, const int *rates)
 {
 	int i = 0;
@@ -1624,6 +1593,8 @@ intel_dp_compute_config(struct intel_encoder *encoder,
 	int common_rates[DP_MAX_SUPPORTED_RATES] = {};
 	int common_len;
 	uint8_t link_bw, rate_select;
+	bool reduce_m_n = drm_dp_has_quirk(&intel_dp->desc,
+					   DP_DPCD_QUIRK_LIMITED_M_N);
 
 	common_len = intel_dp_common_rates(intel_dp, common_rates);
 
@@ -1753,7 +1724,8 @@ found:
 	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,
+			       reduce_m_n);
 
 	if (intel_connector->panel.downclock_mode != NULL &&
 		dev_priv->drrs.type == SEAMLESS_DRRS_SUPPORT) {
@@ -1761,7 +1733,8 @@ found:
 			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,
+				reduce_m_n);
 	}
 
 	/*
@@ -3622,7 +3595,8 @@ intel_edp_init_dpcd(struct intel_dp *intel_dp)
 	if (!intel_dp_read_dpcd(intel_dp))
 		return false;
 
-	intel_dp_read_desc(intel_dp);
+	drm_dp_read_desc(&intel_dp->aux, &intel_dp->desc,
+			 drm_dp_is_branch(intel_dp->dpcd));
 
 	if (intel_dp->dpcd[DP_DPCD_REV] >= 0x11)
 		dev_priv->no_aux_handshake = intel_dp->dpcd[DP_MAX_DOWNSPREAD] &
@@ -4624,7 +4598,8 @@ intel_dp_long_pulse(struct intel_connector *intel_connector)
 
 	intel_dp_print_rates(intel_dp);
 
-	intel_dp_read_desc(intel_dp);
+	drm_dp_read_desc(&intel_dp->aux, &intel_dp->desc,
+			 drm_dp_is_branch(intel_dp->dpcd));
 
 	intel_dp_configure_mst(intel_dp);
 
diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
index c1f62eb07c07..989e25577ac0 100644
--- a/drivers/gpu/drm/i915/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/intel_dp_mst.c
@@ -44,6 +44,8 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
 	int lane_count, slots;
 	const struct drm_display_mode *adjusted_mode = &pipe_config->base.adjusted_mode;
 	int mst_pbn;
+	bool reduce_m_n = drm_dp_has_quirk(&intel_dp->desc,
+					   DP_DPCD_QUIRK_LIMITED_M_N);
 
 	pipe_config->has_pch_encoder = false;
 	bpp = 24;
@@ -75,7 +77,8 @@ 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,
+			       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 aaee3949a422..f630c7af5020 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -906,14 +906,6 @@ enum link_m_n_set {
 	M2_N2
 };
 
-struct intel_dp_desc {
-	u8 oui[3];
-	u8 device_id[6];
-	u8 hw_rev;
-	u8 sw_major_rev;
-	u8 sw_minor_rev;
-} __packed;
-
 struct intel_dp_compliance_data {
 	unsigned long edid;
 	uint8_t video_pattern;
@@ -957,7 +949,7 @@ struct intel_dp {
 	/* Max link BW for the sink as per DPCD registers */
 	int max_sink_link_bw;
 	/* sink or branch descriptor */
-	struct intel_dp_desc desc;
+	struct drm_dp_desc desc;
 	struct drm_dp_aux aux;
 	enum intel_display_power_domain aux_power_domain;
 	uint8_t train_set[4];
@@ -1532,9 +1524,6 @@ static inline unsigned int intel_dp_unused_lane_mask(int lane_count)
 }
 
 bool intel_dp_read_dpcd(struct intel_dp *intel_dp);
-bool __intel_dp_read_desc(struct intel_dp *intel_dp,
-			  struct intel_dp_desc *desc);
-bool intel_dp_read_desc(struct intel_dp *intel_dp);
 int intel_dp_link_required(int pixel_clock, int bpp);
 int intel_dp_max_data_rate(int max_link_clock, int max_lanes);
 bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
diff --git a/drivers/gpu/drm/i915/intel_lspcon.c b/drivers/gpu/drm/i915/intel_lspcon.c
index 71cbe9c08932..5abef482eacf 100644
--- a/drivers/gpu/drm/i915/intel_lspcon.c
+++ b/drivers/gpu/drm/i915/intel_lspcon.c
@@ -240,7 +240,7 @@ bool lspcon_init(struct intel_digital_port *intel_dig_port)
 		return false;
 	}
 
-	intel_dp_read_desc(dp);
+	drm_dp_read_desc(&dp->aux, &dp->desc, drm_dp_is_branch(dp->dpcd));
 
 	DRM_DEBUG_KMS("Success: LSPCON init\n");
 	return true;
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index c0bd0d7651a9..bb837310c07e 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -913,4 +913,55 @@ void drm_dp_aux_unregister(struct drm_dp_aux *aux);
 int drm_dp_start_crc(struct drm_dp_aux *aux, struct drm_crtc *crtc);
 int drm_dp_stop_crc(struct drm_dp_aux *aux);
 
+struct drm_dp_dpcd_ident {
+	u8 oui[3];
+	u8 device_id[6];
+	u8 hw_rev;
+	u8 sw_major_rev;
+	u8 sw_minor_rev;
+} __packed;
+
+/**
+ * struct drm_dp_desc - DP branch/sink device descriptor
+ * @ident: DP device identification from DPCD 0x400 (sink) or 0x500 (branch).
+ * @quirks: Quirks; use drm_dp_has_quirk() to query for the quirks.
+ */
+struct drm_dp_desc {
+	struct drm_dp_dpcd_ident ident;
+	u32 quirks;
+};
+
+int drm_dp_read_desc(struct drm_dp_aux *aux, struct drm_dp_desc *desc,
+		     bool is_branch);
+
+/**
+ * enum drm_dp_quirk - Display Port sink/branch device specific quirks
+ *
+ * Display Port sink and branch devices in the wild have a variety of bugs, try
+ * to collect them here. The quirks are shared, but it's up to the drivers to
+ * implement workarounds for them.
+ */
+enum drm_dp_quirk {
+	/**
+	 * @DP_DPCD_QUIRK_LIMITED_M_N:
+	 *
+	 * The device requires main link attributes Mvid and Nvid to be limited
+	 * to 16 bits.
+	 */
+	DP_DPCD_QUIRK_LIMITED_M_N,
+};
+
+/**
+ * drm_dp_has_quirk() - does the DP device have a specific quirk
+ * @desc: Device decriptor filled by drm_dp_read_desc()
+ * @quirk: Quirk to query for
+ *
+ * Return true if DP device identified by @desc has @quirk.
+ */
+static inline bool
+drm_dp_has_quirk(const struct drm_dp_desc *desc, enum drm_dp_quirk quirk)
+{
+	return desc->quirks & BIT(quirk);
+}
+
 #endif /* _DRM_DP_HELPER_H_ */