Abel Vesa
2024-Oct-31 15:12 UTC
[PATCH RFC 0/4] drm/dp: Rework LTTPR transparent mode handling and add support to msm driver
Looking at both i915 and nouveau DP drivers, both are setting the first
LTTPR (if found) in transparent mode first and then in non-transparent
mode, just like the DP v2.0 specification mentions in section 3.6.6.1.
Being part of the standard, setting the LTTPR in a specific operation mode
can be easily moved in the generic framework. So do that by adding a new
helper.
Then, the msm DP driver is lacking any kind of support for LTTPR handling,
so add it by reading the LTTPR caps for figuring out the number of LTTPRs
found on plug detect and then do exactly what the i915 and nouveau drivers
do with respect to toggling through operating modes, just like the
up-mentioned section from DP spec describes.
At some point, link training per sub-segment will probably be needed, but
for now, toggling the operating modes seems to be enough at least for the
X Elite-based platforms that this patchset has been tested on.
Signed-off-by: Abel Vesa <abel.vesa at linaro.org>
---
Abel Vesa (4):
drm/dp: Add helper to set LTTPRs in transparent mode
drm/nouveau/dp: Use the generic helper to control LTTPR transparent mode
drm/i915/dp: Use the generic helper to control LTTPR transparent mode
drm/msm/dp: Add support for LTTPR handling
drivers/gpu/drm/display/drm_dp_helper.c | 17 +++++++++++++++
.../gpu/drm/i915/display/intel_dp_link_training.c | 2 +-
drivers/gpu/drm/msm/dp/dp_display.c | 25 ++++++++++++++++++++++
drivers/gpu/drm/nouveau/nouveau_dp.c | 9 +++-----
include/drm/display/drm_dp_helper.h | 1 +
5 files changed, 47 insertions(+), 7 deletions(-)
---
base-commit: 6fb2fa9805c501d9ade047fc511961f3273cdcb5
change-id: 20241031-drm-dp-msm-add-lttpr-transparent-mode-set-136cd5bfde07
Best regards,
--
Abel Vesa <abel.vesa at linaro.org>
Abel Vesa
2024-Oct-31 15:12 UTC
[PATCH RFC 1/4] drm/dp: Add helper to set LTTPRs in transparent mode
According to the DisplayPort standard, LTTPRs have two operating
modes:
- non-transparent - it replies to DPCD LTTPR field specific AUX
requests, while passes through all other AUX requests
- transparent - it passes through all AUX requests.
Switching between this two modes is done by the DPTX by issuing
an AUX write to the DPCD PHY_REPEATER_MODE register.
Add a generic helper that allows switching between these modes.
Signed-off-by: Abel Vesa <abel.vesa at linaro.org>
---
drivers/gpu/drm/display/drm_dp_helper.c | 17 +++++++++++++++++
include/drm/display/drm_dp_helper.h | 1 +
2 files changed, 18 insertions(+)
diff --git a/drivers/gpu/drm/display/drm_dp_helper.c
b/drivers/gpu/drm/display/drm_dp_helper.c
index
6ee51003de3ce616c3a52653c2f1979ad7658e21..38d612345986ad54b42228902ea718a089d169c4
100644
--- a/drivers/gpu/drm/display/drm_dp_helper.c
+++ b/drivers/gpu/drm/display/drm_dp_helper.c
@@ -2694,6 +2694,23 @@ int drm_dp_lttpr_max_link_rate(const u8
caps[DP_LTTPR_COMMON_CAP_SIZE])
}
EXPORT_SYMBOL(drm_dp_lttpr_max_link_rate);
+/**
+ * drm_dp_lttpr_set_transparent_mode - set the LTTPR in transparent mode
+ * @aux: DisplayPort AUX channel
+ * @enable: Enable or disable transparent mode
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+
+int drm_dp_lttpr_set_transparent_mode(struct drm_dp_aux *aux, bool enable)
+{
+ u8 val = enable ? DP_PHY_REPEATER_MODE_TRANSPARENT :
+ DP_PHY_REPEATER_MODE_NON_TRANSPARENT;
+
+ return drm_dp_dpcd_writeb(aux, DP_PHY_REPEATER_MODE, val);
+}
+EXPORT_SYMBOL(drm_dp_lttpr_set_transparent_mode);
+
/**
* drm_dp_lttpr_max_lane_count - get the maximum lane count supported by all
LTTPRs
* @caps: LTTPR common capabilities
diff --git a/include/drm/display/drm_dp_helper.h
b/include/drm/display/drm_dp_helper.h
index
279624833ea9259809428162f4e845654359f8c9..8821ab2d36b0e04d38ccbdddcb703b34de7ed680
100644
--- a/include/drm/display/drm_dp_helper.h
+++ b/include/drm/display/drm_dp_helper.h
@@ -625,6 +625,7 @@ int drm_dp_read_lttpr_phy_caps(struct drm_dp_aux *aux,
u8 caps[DP_LTTPR_PHY_CAP_SIZE]);
int drm_dp_lttpr_count(const u8 cap[DP_LTTPR_COMMON_CAP_SIZE]);
int drm_dp_lttpr_max_link_rate(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE]);
+int drm_dp_lttpr_set_transparent_mode(struct drm_dp_aux *aux, bool enable);
int drm_dp_lttpr_max_lane_count(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE]);
bool drm_dp_lttpr_voltage_swing_level_3_supported(const u8
caps[DP_LTTPR_PHY_CAP_SIZE]);
bool drm_dp_lttpr_pre_emphasis_level_3_supported(const u8
caps[DP_LTTPR_PHY_CAP_SIZE]);
--
2.34.1
Abel Vesa
2024-Oct-31 15:12 UTC
[PATCH RFC 2/4] drm/nouveau/dp: Use the generic helper to control LTTPR transparent mode
LTTPRs operating modes are defined by the DisplayPort standard and the
generic framework now provides a helper to switch between them.
So use the drm generic helper instead as it makes the code a bit cleaner.
Signed-off-by: Abel Vesa <abel.vesa at linaro.org>
---
drivers/gpu/drm/nouveau/nouveau_dp.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/nouveau/nouveau_dp.c
b/drivers/gpu/drm/nouveau/nouveau_dp.c
index
bcda0105160f1450df855281e0d932606a5095dd..80264e6186246903fa037861fe37493646de0c6e
100644
--- a/drivers/gpu/drm/nouveau/nouveau_dp.c
+++ b/drivers/gpu/drm/nouveau/nouveau_dp.c
@@ -80,15 +80,12 @@ nouveau_dp_probe_dpcd(struct nouveau_connector
*nv_connector,
int nr = drm_dp_lttpr_count(outp->dp.lttpr.caps);
if (nr) {
- drm_dp_dpcd_writeb(aux, DP_PHY_REPEATER_MODE,
- DP_PHY_REPEATER_MODE_TRANSPARENT);
+ drm_dp_lttpr_set_transparent_mode(aux, true);
if (nr > 0) {
- ret = drm_dp_dpcd_writeb(aux, DP_PHY_REPEATER_MODE,
- DP_PHY_REPEATER_MODE_NON_TRANSPARENT);
+ ret = drm_dp_lttpr_set_transparent_mode(aux, false);
if (ret != 1) {
- drm_dp_dpcd_writeb(aux, DP_PHY_REPEATER_MODE,
- DP_PHY_REPEATER_MODE_TRANSPARENT);
+ drm_dp_lttpr_set_transparent_mode(aux, true);
} else {
outp->dp.lttpr.nr = nr;
}
--
2.34.1
Abel Vesa
2024-Oct-31 15:12 UTC
[PATCH RFC 3/4] drm/i915/dp: Use the generic helper to control LTTPR transparent mode
LTTPRs operating modes are defined by the DisplayPort standard and the generic framework now provides a helper to switch between them. So use the drm generic helper instead as it makes the code a bit cleaner. Signed-off-by: Abel Vesa <abel.vesa at linaro.org> --- drivers/gpu/drm/i915/display/intel_dp_link_training.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c index 397cc4ebae526a416fcda9c74f57a8f9f803ce3b..0038608d29219ff1423a649089a38980e95b87e4 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c @@ -118,7 +118,7 @@ intel_dp_set_lttpr_transparent_mode(struct intel_dp *intel_dp, bool enable) u8 val = enable ? DP_PHY_REPEATER_MODE_TRANSPARENT : DP_PHY_REPEATER_MODE_NON_TRANSPARENT; - if (drm_dp_dpcd_write(&intel_dp->aux, DP_PHY_REPEATER_MODE, &val, 1) != 1) + if (drm_dp_lttpr_set_transparent_mode(&intel_dp->aux, enable) != 1) return false; intel_dp->lttpr_common_caps[DP_PHY_REPEATER_MODE - -- 2.34.1
Abel Vesa
2024-Oct-31 15:12 UTC
[PATCH RFC 4/4] drm/msm/dp: Add support for LTTPR handling
Link Training Tunable PHY Repeaters (LTTPRs) are defined in DisplayPort
1.4a specification. As the name suggests, these PHY repeaters are
capable of adjusting their output for link training purposes.
The msm DP driver is currently lacking any handling of LTTPRs.
This means that if at least one LTTPR is found between DPTX and DPRX,
the link training would fail if that LTTPR was not already configured
in transparent mode.
The section 3.6.6.1 from the DisplayPort v2.0 specification mandates
that before link training with the LTTPR is started, the DPTX may place
the LTTPR in non-transparent mode by first switching to transparent mode
and then to non-transparent mode. This operation seems to be needed only
on first link training and doesn't need to be done again until device is
unplugged.
It has been observed on a few X Elite-based platforms which have
such LTTPRs in their board design that the DPTX needs to follow the
procedure described above in order for the link training to be successful.
So add support for reading the LTTPR DPCD caps to figure out the number
of such LTTPRs first. Then, for platforms (or Type-C dongles) that have
at least one such an LTTPR, set its operation mode to transparent mode
first and then to non-transparent, just like the mentioned section of
the specification mandates.
Signed-off-by: Abel Vesa <abel.vesa at linaro.org>
---
drivers/gpu/drm/msm/dp/dp_display.c | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)
diff --git a/drivers/gpu/drm/msm/dp/dp_display.c
b/drivers/gpu/drm/msm/dp/dp_display.c
index
f01980b0888a40b719d3958cb96c6341feada077..5d3d318d7b87ce3bf567d8b7435931d8e087f713
100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -107,6 +107,8 @@ struct dp_display_private {
struct dp_event event_list[DP_EVENT_Q_MAX];
spinlock_t event_lock;
+ u8 lttpr_caps[DP_LTTPR_COMMON_CAP_SIZE];
+
bool wide_bus_supported;
struct dp_audio *audio;
@@ -367,12 +369,35 @@ static int dp_display_send_hpd_notification(struct
dp_display_private *dp,
return 0;
}
+static void dp_display_lttpr_init(struct dp_display_private *dp)
+{
+ int lttpr_count;
+
+ if (drm_dp_read_lttpr_common_caps(dp->aux, dp->panel->dpcd,
+ dp->lttpr_caps))
+ return;
+
+ lttpr_count = drm_dp_lttpr_count(dp->lttpr_caps);
+
+ if (lttpr_count) {
+ drm_dp_lttpr_set_transparent_mode(dp->aux, true);
+
+ if (lttpr_count > 0) {
+ if (drm_dp_lttpr_set_transparent_mode(dp->aux, false) != 1)
+ drm_dp_lttpr_set_transparent_mode(dp->aux, true);
+ }
+ }
+}
+
static int dp_display_process_hpd_high(struct dp_display_private *dp)
{
struct drm_connector *connector = dp->dp_display.connector;
const struct drm_display_info *info = &connector->display_info;
int rc = 0;
+ if (!dp->dp_display.is_edp)
+ dp_display_lttpr_init(dp);
+
rc = dp_panel_read_sink_caps(dp->panel, connector);
if (rc)
goto end;
--
2.34.1