[PATCH v7 1/5] drm: Read DP branch device HW revision

[Mika Kahola]

HW revision is mandatory field for DisplayPort branch
devices. This is defined in DPCD register field 0x509.

v2: move drm_dp_ds_revision structure to be part of
    drm_dp_link structure (Daniel)

Signed-off-by: Mika Kahola <mika.kahola at intel.com>
---
 drivers/gpu/drm/drm_dp_helper.c  | 27 +++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_drv.h |  1 +
 include/drm/drm_dp_helper.h      |  9 +++++++++
 3 files changed, 37 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 75b2873..5fecdc1 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -514,6 +514,33 @@ int drm_dp_downstream_max_bpc(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
 EXPORT_SYMBOL(drm_dp_downstream_max_bpc);
 
 /**
+ * drm_dp_downstream_hw_rev() - read DP branch device HW revision
+ * @aux: DisplayPort AUX channel
+ *
+ * Returns 0 on succes or negative error code on failure
+ */
+int drm_dp_downstream_hw_rev(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
+			     struct drm_dp_aux *aux, struct drm_dp_link *link)
+{
+	uint8_t tmp;
+	int err;
+
+	if (!(dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_PRESENT))
+		return -EINVAL;
+
+	err = drm_dp_dpcd_read(aux, DP_BRANCH_HW_REV, &tmp, 1);
+
+	if (err < 0)
+		return err;
+
+	link->ds_hw_rev.major = (tmp & 0xf0) >> 4;
+	link->ds_hw_rev.minor = tmp & 0xf;
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_dp_downstream_hw_rev);
+
+/**
  * drm_dp_downstream_id() - identify branch device
  * @aux: DisplayPort AUX channel
  *
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index e74d851..a6eccf5 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -865,6 +865,7 @@ struct intel_dp {
 	uint8_t num_sink_rates;
 	int sink_rates[DP_MAX_SUPPORTED_RATES];
 	struct drm_dp_aux aux;
+	struct drm_dp_link link;
 	uint8_t train_set[4];
 	int panel_power_up_delay;
 	int panel_power_down_delay;
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 8e1fe58..1127948 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -446,6 +446,7 @@
 #define DP_SINK_OUI			    0x400
 #define DP_BRANCH_OUI			    0x500
 #define DP_BRANCH_ID                        0x503
+#define DP_BRANCH_HW_REV                    0x509
 
 #define DP_SET_POWER                        0x600
 # define DP_SET_POWER_D0                    0x1
@@ -803,11 +804,17 @@ int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux,
  */
 #define DP_LINK_CAP_ENHANCED_FRAMING (1 << 0)
 
+struct drm_dp_ds_revision {
+	int major;
+	int minor;
+};
+
 struct drm_dp_link {
 	unsigned char revision;
 	unsigned int rate;
 	unsigned int num_lanes;
 	unsigned long capabilities;
+	struct drm_dp_ds_revision ds_hw_rev;
 };
 
 int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link);
@@ -819,6 +826,8 @@ 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]);
+int drm_dp_downstream_hw_rev(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
+			     struct drm_dp_aux *aux, struct drm_dp_link *link);
 
 void drm_dp_aux_init(struct drm_dp_aux *aux);
 int drm_dp_aux_register(struct drm_dp_aux *aux);
-- 
1.9.1