SW revision is mandatory field for DisplayPort branch
devices. This is defined in DPCD register field 0x50A.
Signed-off-by: Mika Kahola <mika.kahola@xxxxxxxxx>
---
drivers/gpu/drm/drm_dp_helper.c | 21 +++++++++++++++++++++
include/drm/drm_dp_helper.h | 2 ++
2 files changed, 23 insertions(+)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index b5ae189..80147cd 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -535,6 +535,27 @@ struct drm_dp_revision drm_dp_downstream_hw_rev(struct drm_dp_aux *aux)
EXPORT_SYMBOL(drm_dp_downstream_hw_rev);
/**
+ * drm_dp_downstream_sw_rev() - read DP branch device SW revision
+ * @aux: DisplayPort AUX channel
+ *
+ * Returns SW revision on success or negative error code on failure
+ */
+struct drm_dp_revision drm_dp_downstream_sw_rev(struct drm_dp_aux *aux)
+{
+ uint8_t tmp[2];
+ struct drm_dp_revision rev = { .major = -EINVAL, .minor = -EINVAL };
+
+ if (drm_dp_dpcd_read(aux, DP_BRANCH_SW_REV, tmp, 2) != 2)
+ return rev;
+
+ rev.major = tmp[0];
+ rev.minor = tmp[1];
+
+ return rev;
+}
+EXPORT_SYMBOL(drm_dp_downstream_sw_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 641bf3d..c3e4759 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
@@ -819,6 +820,7 @@ 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);
+struct drm_dp_revision drm_dp_downstream_sw_rev(struct drm_dp_aux *aux);
int drm_dp_aux_register(struct drm_dp_aux *aux);
void drm_dp_aux_unregister(struct drm_dp_aux *aux);
--
1.9.1
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