[PATCH v6 06/10] drm: Read DP branch device HW revision

[Mika Kahola <mika.kahola@xxxxxxxxx>]

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

Signed-off-by: Mika Kahola <mika.kahola@xxxxxxxxx>
---
 drivers/gpu/drm/drm_dp_helper.c | 21 +++++++++++++++++++++
 include/drm/drm_dp_helper.h     |  7 +++++++
 2 files changed, 28 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 4003464..cfd75df 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -514,6 +514,27 @@ 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 HW revision on succes or negative error code on failure
+ */
+struct drm_dp_revision drm_dp_downstream_hw_rev(struct drm_dp_aux *aux)
+{
+	uint8_t tmp;
+	struct drm_dp_revision rev = { .major = -EINVAL, .minor = -EINVAL };
+
+	if (drm_dp_dpcd_read(aux, DP_BRANCH_HW_REV, &tmp, 1) != 1)
+		return rev;
+
+	rev.major = (tmp & 0xf0) >> 4;
+	rev.minor = tmp & 0xf;
+
+	return rev;
+}
+EXPORT_SYMBOL(drm_dp_downstream_hw_rev);
+
+/**
  * drm_dp_downstream_id() - identify branch device
  * @aux: DisplayPort AUX channel
  *
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 8264d54..5f577e4 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
@@ -803,6 +804,11 @@ struct drm_dp_link {
 	unsigned long capabilities;
 };
 
+struct drm_dp_revision {
+       int major;
+       int minor;
+};
+
 int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link);
 int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link);
 int drm_dp_link_power_down(struct drm_dp_aux *aux, struct drm_dp_link *link);
@@ -812,6 +818,7 @@ 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]);
+struct drm_dp_revision drm_dp_downstream_hw_rev(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);
-- 
1.9.1

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