drm/i915: Read DP branch device SW revision

SW revision is mandatory field for DisplayPort branch
devices. This is defined in DPCD register fields 0x50A
and 0x50B.

v2: move drm_dp_ds_revision structure to be part of
    drm_dp_link structure (Daniel)
v3: remove dependency to drm_dp_helper but instead parse
    DPCD and print SW revision info to dmesg (Ville)
v4: commit message fix (Jim Bride)

Signed-off-by: Mika Kahola <mika.kahola@intel.com>
Reviewed-by: Jim Bride <jim.bride@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1473419458-17080-9-git-send-email-mika.kahola@intel.com

2 files changed, 21 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index bb0417c52154..7428c729ed4e 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1438,6 +1438,25 @@ static void intel_dp_print_hw_revision(struct intel_dp *intel_dp)
         DRM_DEBUG_KMS("sink hw revision: %d.%d\n", (rev & 0xf0) >> 4, rev & 0xf);
 }
 
+static void intel_dp_print_sw_revision(struct intel_dp *intel_dp)
+{
+        uint8_t rev[2];
+        int len;
+
+        if ((drm_debug & DRM_UT_KMS) == 0)
+                return;
+
+        if (!(intel_dp->dpcd[DP_DOWNSTREAMPORT_PRESENT] &
+              DP_DWN_STRM_PORT_PRESENT))
+                return;
+
+        len = drm_dp_dpcd_read(&intel_dp->aux, DP_BRANCH_SW_REV, &rev, 2);
+        if (len < 0)
+                return;
+
+        DRM_DEBUG_KMS("sink sw revision: %d.%d\n", rev[0], rev[1]);
+}
+
 static int rate_to_index(int find, const int *rates)
 {
         int i = 0;
@@ -4332,6 +4351,7 @@ intel_dp_long_pulse(struct intel_connector *intel_connector)
         intel_dp_probe_oui(intel_dp);
 
         intel_dp_print_hw_revision(intel_dp);
+        intel_dp_print_sw_revision(intel_dp);
 
         intel_dp_configure_mst(intel_dp);
 
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 19ac59984df0..215202fa5867 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -447,6 +447,7 @@
 #define DP_BRANCH_OUI                       0x500
 #define DP_BRANCH_ID                        0x503
 #define DP_BRANCH_HW_REV                    0x509
+#define DP_BRANCH_SW_REV                    0x50A
 
 #define DP_SET_POWER                        0x600
 # define DP_SET_POWER_D0                    0x1