Read DisplayPort branch device info from through debugfs
interface.

v2: use drm_dp_helper routines to collect data
v3: cleanup to match the drm_dp_helper.c patches introduced
    earlier in this series
v4: move DP branch device info to function 'intel_dp_branch_device_info()'
v5: initial step to move debugging info from intel_dp. to drm_dp_helper.c 
(Daniel)
v6: read hw and sw revision without using specific drm_dp_helper routines
v7: indentation fixes (Jim Bride)

Signed-off-by: Mika Kahola <mika.kahola at intel.com>
---
 drivers/gpu/drm/drm_dp_helper.c     | 85 +++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/i915_debugfs.c |  3 ++
 include/drm/drm_dp_helper.h         |  2 +
 3 files changed, 90 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 01ee7af..a536514 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -526,6 +526,91 @@ int drm_dp_downstream_id(struct drm_dp_aux *aux, char 
id[6])
 }
 EXPORT_SYMBOL(drm_dp_downstream_id);

+/**
+ * drm_dp_downstream_debug() - debug DP branch devices
+ * @m: pointer for debugfs file
+ * @dpcd: DisplayPort configuration data
+ * @port_cap: port capabilities
+ * @aux: DisplayPort AUX channel
+ *
+ */
+void drm_dp_downstream_debug(struct seq_file *m,
+                            const u8 dpcd[DP_RECEIVER_CAP_SIZE],
+                            const u8 port_cap[4], struct drm_dp_aux *aux)
+{
+       bool detailed_cap_info = dpcd[DP_DOWNSTREAMPORT_PRESENT] &
+                                DP_DETAILED_CAP_INFO_AVAILABLE;
+       int clk;
+       int bpc;
+       char id[6];
+       int len;
+       uint8_t rev[2];
+       int type = port_cap[0] & DP_DS_PORT_TYPE_MASK;
+       bool branch_device = dpcd[DP_DOWNSTREAMPORT_PRESENT] &
+                            DP_DWN_STRM_PORT_PRESENT;
+
+       seq_printf(m, "\tDP branch device present: %s\n",
+                  branch_device ? "yes" : "no");
+
+       if (!branch_device)
+               return;
+
+       switch (type) {
+       case DP_DS_PORT_TYPE_DP:
+               seq_puts(m, "\t\tType: DisplayPort\n");
+               break;
+       case DP_DS_PORT_TYPE_VGA:
+               seq_puts(m, "\t\tType: VGA\n");
+               break;
+       case DP_DS_PORT_TYPE_DVI:
+               seq_puts(m, "\t\tType: DVI\n");
+               break;
+       case DP_DS_PORT_TYPE_HDMI:
+               seq_puts(m, "\t\tType: HDMI\n");
+               break;
+       case DP_DS_PORT_TYPE_NON_EDID:
+               seq_puts(m, "\t\tType: others without EDID support\n");
+               break;
+       case DP_DS_PORT_TYPE_DP_DUALMODE:
+               seq_puts(m, "\t\tType: DP++\n");
+               break;
+       case DP_DS_PORT_TYPE_WIRELESS:
+               seq_puts(m, "\t\tType: Wireless\n");
+               break;
+       default:
+               seq_puts(m, "\t\tType: N/A\n");
+       }
+
+       drm_dp_downstream_id(aux, id);
+       seq_printf(m, "\t\tID: %s\n", id);
+
+       len = drm_dp_dpcd_read(aux, DP_BRANCH_HW_REV, &rev[0], 1);
+       if (len > 0)
+               seq_printf(m, "\t\tHW: %d.%d\n",
+                          (rev[0] & 0xf0) >> 4, rev[0] & 0xf);
+
+       len = drm_dp_dpcd_read(aux, DP_BRANCH_SW_REV, &rev, 2);
+       if (len > 0)
+               seq_printf(m, "\t\tSW: %d.%d\n", rev[0], rev[1]);
+
+       if (detailed_cap_info) {
+               clk = drm_dp_downstream_max_clock(dpcd, port_cap);
+
+               if (clk > 0) {
+                       if (type == DP_DS_PORT_TYPE_VGA)
+                               seq_printf(m, "\t\tMax dot clock: %d kHz\n", 
clk);
+                       else
+                               seq_printf(m, "\t\tMax TMDS clock: %d kHz\n", 
clk);
+               }
+
+               bpc = drm_dp_downstream_max_bpc(dpcd, port_cap);
+
+               if (bpc > 0)
+                       seq_printf(m, "\t\tMax bpc: %d\n", bpc);
+       }
+}
+EXPORT_SYMBOL(drm_dp_downstream_debug);
+
 /*
  * I2C-over-AUX implementation
  */
diff --git a/drivers/gpu/drm/i915/i915_debugfs.c 
b/drivers/gpu/drm/i915/i915_debugfs.c
index 02b627e..44fab14 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -2851,6 +2851,9 @@ static void intel_dp_info(struct seq_file *m,
        seq_printf(m, "\taudio support: %s\n", yesno(intel_dp->has_audio));
        if (intel_connector->base.connector_type == DRM_MODE_CONNECTOR_eDP)
                intel_panel_info(m, &intel_connector->panel);
+
+       drm_dp_downstream_debug(m, intel_dp->dpcd, intel_dp->downstream_ports,
+                               &intel_dp->aux);
 }

 static void intel_hdmi_info(struct seq_file *m,
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 215202f..2a79882 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -823,6 +823,8 @@ int drm_dp_downstream_max_clock(const u8 
dpcd[DP_RECEIVER_CAP_SIZE],
 int drm_dp_downstream_max_bpc(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
                              const u8 port_cap[4]);
 int drm_dp_downstream_id(struct drm_dp_aux *aux, char id[6]);
+void drm_dp_downstream_debug(struct seq_file *m, const u8 
dpcd[DP_RECEIVER_CAP_SIZE],
+                            const u8 port_cap[4], struct drm_dp_aux *aux);

 void drm_dp_aux_init(struct drm_dp_aux *aux);
 int drm_dp_aux_register(struct drm_dp_aux *aux);
-- 
2.7.4

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