For CRTCs with multiple outputs (i.e., encoders plus connectors),
only report at most a single connected output to userspace. Make
this configurable via CONFIG_DRM_REPORT_SINGLE_CONNECTED_CRTC_OUTPUT.
Having multiple connected outputs on the same CRTC complicates
display-mode and format selection, so most userspace does not
support this. This is mostly not a problem in practice, as modern
display hardware provides a separate CRTC for each output. On
old hardware or hardware with BMCs, a single CRTC often drives
multiple displays. Only reporting one of them as connected makes
the hardware compatible with common userspace.
Add the field prioritized_connectors to struct drm_connector. The
bitmask signals which other connectors have priority. Also provide
the helper drm_probe_helper_prioritize_connectors() that sets
default priorities for a given set of connectors. Calling the
helper should be enough to set up the functionality for most drivers.
With the prioritization bits in place, update connector-status
detection to test against prioritized conenctors. So when the probe
helpers detect a connector as connected, test against the prioritized
connectors. If any is also connected, set the connector status to
disconnected.
Please note that this functionality is a workaround for limitations
in userspace. If your compositor supports multiple outputs per CRTC,
CONFIG_DRM_REPORT_SINGLE_CONNECTED_CRTC_OUTPUT should be disabled.
Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
---
drivers/gpu/drm/Kconfig | 15 +++++
drivers/gpu/drm/drm_probe_helper.c | 104 +++++++++++++++++++++++++++++
include/drm/drm_connector.h | 2 +
include/drm/drm_probe_helper.h | 2 +
4 files changed, 123 insertions(+)
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index fd0749c0c630..d1afdbd2d93b 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -105,6 +105,21 @@ config DRM_KMS_HELPER
help
CRTC helpers for KMS drivers.
+config DRM_REPORT_SINGLE_CONNECTED_CRTC_OUTPUT
+ bool "Report only a single connected output per CRTC"
+ depends on DRM
+ default n
+ help
+ CRTCs can support multiple encoders and connectors for output.
+ More than one pair can be connected to a display at a time. Most
+ userspace only supports at most one connected output per CRTC at a
+ time. Enable this option to let DRM report at most one connected
+ output per CRTC. This is mostly relevant for low-end and old
+ hardware. Most modern graphics hardware supports a separate CRTC
+ per output and won't be affected by this setting.
+
+ If in doubt, say "Y".
+
config DRM_PANIC
bool "Display a user-friendly message when a kernel panic occurs"
depends on DRM && !(FRAMEBUFFER_CONSOLE && VT_CONSOLE)
diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
index f14301abf53f..fc0652635148 100644
--- a/drivers/gpu/drm/drm_probe_helper.c
+++ b/drivers/gpu/drm/drm_probe_helper.c
@@ -352,6 +352,74 @@ static int detect_connector_status(struct drm_connector *connector,
return connector_status_connected;
}
+static int reported_connector_status(struct drm_connector *connector, int detected_status,
+ struct drm_modeset_acquire_ctx *ctx, bool force)
+{
+#if defined(CONFIG_DRM_REPORT_SINGLE_CONNECTED_CRTC_OUTPUT)
+ struct drm_connector *prio_connector = connector;
+ struct drm_device *dev = connector->dev;
+ struct drm_connector_list_iter iter;
+ struct drm_connector *pos;
+ u32 connector_mask;
+ int ret = 0;
+
+ if (!connector->prioritized_connectors)
+ return detected_status;
+
+ if (detected_status != connector_status_connected)
+ return detected_status;
+
+ connector_mask = drm_connector_mask(connector);
+
+ /*
+ * Find the connector with status 'connected' and a higher
+ * priority.
+ */
+ drm_connector_list_iter_begin(dev, &iter);
+ drm_for_each_connector_iter(pos, &iter) {
+ if (!(drm_connector_mask(pos) & connector->prioritized_connectors))
+ continue;
+
+ /*
+ * Warn if connector has priority over itself.
+ */
+ if (drm_WARN_ON_ONCE(dev, pos == connector))
+ continue;
+
+ /*
+ * Warn if both connectors have priority over each other. Pick the
+ * one with the lower index.
+ */
+ if (drm_WARN_ON_ONCE(dev, pos->prioritized_connectors & connector_mask)) {
+ if (pos->index > connector->index)
+ continue;
+ }
+
+ ret = detect_connector_status(pos, ctx, force);
+ if (ret < 0)
+ break;
+ if (ret == connector_status_disconnected)
+ continue;
+
+ prio_connector = pos;
+ break;
+ }
+ drm_connector_list_iter_end(&iter);
+
+ if (ret < 0)
+ return ret;
+
+ /*
+ * We've found another connected connector. Report our connector
+ * as 'disconnected'.
+ */
+ if (prio_connector != connector)
+ detected_status = connector_status_disconnected;
+#endif
+
+ return detected_status;
+}
+
static enum drm_connector_status
drm_helper_probe_detect_ctx(struct drm_connector *connector, bool force)
{
@@ -373,6 +441,12 @@ drm_helper_probe_detect_ctx(struct drm_connector *connector, bool force)
if (WARN_ON(ret < 0))
ret = connector_status_unknown;
+ ret = reported_connector_status(connector, ret, &ctx, force);
+ if (ret == -EDEADLK) {
+ drm_modeset_backoff(&ctx);
+ goto retry;
+ }
+
if (ret != connector->status)
connector->epoch_counter += 1;
@@ -408,6 +482,7 @@ drm_helper_probe_detect(struct drm_connector *connector,
return ret;
ret = detect_connector_status(connector, ctx, force);
+ ret = reported_connector_status(connector, ret, ctx, force);
if (ret != connector->status)
connector->epoch_counter += 1;
@@ -416,6 +491,35 @@ drm_helper_probe_detect(struct drm_connector *connector,
}
EXPORT_SYMBOL(drm_helper_probe_detect);
+/**
+ * drm_probe_helper_prioritize_connectors - Set connector priorities
+ * @dev: the DRM device with connectors
+ * @connector_mask: Bitmask connector indices
+ *
+ * drm_probe_helper_prioritize_connectors() prioritizes all connectors
+ * specified in @connector_mask. All given connectors are assumed to
+ * interfere with each other. Connectors with a lower index have priority
+ * over connectors with a higher index.
+ */
+void drm_probe_helper_prioritize_connectors(struct drm_device *dev, u32 connector_mask)
+{
+ struct drm_connector_list_iter iter;
+ struct drm_connector *connector;
+ u32 prioritized_connectors = 0;
+
+ drm_connector_list_iter_begin(dev, &iter);
+ drm_for_each_connector_iter(connector, &iter) {
+ u32 mask = drm_connector_mask(connector);
+
+ if (!(mask & connector_mask))
+ continue;
+ connector->prioritized_connectors = prioritized_connectors;
+ prioritized_connectors |= mask;
+ }
+ drm_connector_list_iter_end(&iter);
+}
+EXPORT_SYMBOL(drm_probe_helper_prioritize_connectors);
+
static int drm_helper_probe_get_modes(struct drm_connector *connector)
{
const struct drm_connector_helper_funcs *connector_funcs =
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 5ad735253413..e3039478e928 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -1985,6 +1985,8 @@ struct drm_connector {
/** @epoch_counter: used to detect any other changes in connector, besides status */
u64 epoch_counter;
+ u32 prioritized_connectors;
+
/**
* @possible_encoders: Bit mask of encoders that can drive this
* connector, drm_encoder_index() determines the index into the bitfield
diff --git a/include/drm/drm_probe_helper.h b/include/drm/drm_probe_helper.h
index d6ce7b218b77..05e23485550d 100644
--- a/include/drm/drm_probe_helper.h
+++ b/include/drm/drm_probe_helper.h
@@ -17,6 +17,8 @@ int drm_helper_probe_detect(struct drm_connector *connector,
struct drm_modeset_acquire_ctx *ctx,
bool force);
+void drm_probe_helper_prioritize_connectors(struct drm_device *dev, u32 connector_mask);
+
int drmm_kms_helper_poll_init(struct drm_device *dev);
void drm_kms_helper_poll_init(struct drm_device *dev);
void drm_kms_helper_poll_fini(struct drm_device *dev);
--
2.45.2
