From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Add a small helper to parse from the DPCD whether link training
is required when exiting PSR main-link off mode.
v2: Rebased
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/drm_dp_helper.c | 14 ++++++++++++++
include/drm/drm_dp_helper.h | 1 +
2 files changed, 15 insertions(+)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 1f914629031e..cc7b55a695b5 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -854,3 +854,17 @@ int drm_dp_psr_setup_time(const u8 psr_cap[EDP_PSR_RECEIVER_CAP_SIZE])
EXPORT_SYMBOL(drm_dp_psr_setup_time);
#undef PSR_SETUP_TIME
+
+/**
+ * drm_dp_psr_need_train_on_exit() - Indicate whether link training is needed on PSR exit
+ * @psr_cap: PSR capabilities from DPCD
+ *
+ * Returns:
+ * Whether link training is required when exiting PSR main-link off mode.
+ */
+bool drm_dp_psr_need_train_on_exit(const u8 psr_cap[EDP_PSR_RECEIVER_CAP_SIZE])
+{
+ /* DP_PSR_NO_TRAIN_ON_EXIT is "don't care" for PSR2 capable devices */
+ return psr_cap[0] < 0x2 && (psr_cap[1] & DP_PSR_NO_TRAIN_ON_EXIT) == 0;
+}
+EXPORT_SYMBOL(drm_dp_psr_need_train_on_exit);
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 6aa74f7d45b4..2437f1b6e776 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -658,6 +658,7 @@ struct edp_vsc_psr {
#define EDP_VSC_PSR_CRC_VALUES_VALID (1<<2)
int drm_dp_psr_setup_time(const u8 psr_cap[EDP_PSR_RECEIVER_CAP_SIZE]);
+bool drm_dp_psr_need_train_on_exit(const u8 psr_cap[EDP_PSR_RECEIVER_CAP_SIZE]);
static inline int
drm_dp_max_link_rate(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
--
2.7.4
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