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usb: typec: altmodes/displayport: add irq_hpd to sysfs

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Add irq_hpd sysfs node to displayport driver. This allows the userspace
to subscribe to irq events similar to how it can subscribe to changes in
hpd.

irq_hpd is read only and returns the number of irq events generated since
driver probe. pending_irq_hpd is added so that a sysfs_emit can be
generated if the HPD high event belonging to the same status message
is delayed until a successful configuration.

Signed-off-by: RD Babiera <rdbabiera@google.com>
Reviewed-by: Badhri Jagan Sridharan <badhri@google.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20250623204947.732915-2-rdbabiera@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
RD Babiera
2025-06-23 20:49:45 +00:00
committed by Greg Kroah-Hartman
parent 9962d0433a
commit 8b4f6fafed
2 changed files with 38 additions and 0 deletions
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10
Documentation/ABI/testing/sysfs-driver-typec-displayport
View File

@@ -62,3 +62,13 @@ Description:
by VESA DisplayPort Alt Mode on USB Type-C Standard.
- 0 when HPD’s logical state is low (HPD_Low) as defined by
VESA DisplayPort Alt Mode on USB Type-C Standard.
What: /sys/bus/typec/devices/.../displayport/irq_hpd
Date: June 2025
Contact: RD Babiera <rdbabiera@google.com>
Description:
IRQ_HPD events are sent over the USB PD protocol in Status Update and
Attention messages. IRQ_HPD can only be asserted when HPD is high,
and is asserted when an IRQ_HPD has been issued since the last Status
Update. This is a read only node that returns the number of IRQ events
raised in the driver's lifetime.

28
drivers/usb/typec/altmodes/displayport.c
View File

@@ -65,6 +65,13 @@ struct dp_altmode {
enum dp_state state;
bool hpd;
bool pending_hpd;
u32 irq_hpd_count;
/*
* hpd is mandatory for irq_hpd assertion, so irq_hpd also needs its own pending flag if
* both hpd and irq_hpd are asserted in the first Status Update before the pin assignment
* is configured.
*/
bool pending_irq_hpd;
struct mutex lock; /* device lock */
struct work_struct work;
@@ -151,6 +158,7 @@ static int dp_altmode_status_update(struct dp_altmode *dp)
{
bool configured = !!DP_CONF_GET_PIN_ASSIGN(dp->data.conf);
bool hpd = !!(dp->data.status & DP_STATUS_HPD_STATE);
bool irq_hpd = !!(dp->data.status & DP_STATUS_IRQ_HPD);
u8 con = DP_STATUS_CONNECTION(dp->data.status);
int ret = 0;
@@ -170,6 +178,8 @@ static int dp_altmode_status_update(struct dp_altmode *dp)
dp->hpd = hpd;
dp->pending_hpd = true;
}
if (dp->hpd && dp->pending_hpd && irq_hpd)
dp->pending_irq_hpd = true;
}
} else {
drm_connector_oob_hotplug_event(dp->connector_fwnode,
@@ -177,6 +187,10 @@ static int dp_altmode_status_update(struct dp_altmode *dp)
connector_status_disconnected);
dp->hpd = hpd;
sysfs_notify(&dp->alt->dev.kobj, "displayport", "hpd");
if (hpd && irq_hpd) {
dp->irq_hpd_count++;
sysfs_notify(&dp->alt->dev.kobj, "displayport", "irq_hpd");
}
}
return ret;
@@ -196,6 +210,11 @@ static int dp_altmode_configured(struct dp_altmode *dp)
connector_status_connected);
sysfs_notify(&dp->alt->dev.kobj, "displayport", "hpd");
dp->pending_hpd = false;
if (dp->pending_irq_hpd) {
dp->irq_hpd_count++;
sysfs_notify(&dp->alt->dev.kobj, "displayport", "irq_hpd");
dp->pending_irq_hpd = false;
}
}
return dp_altmode_notify(dp);
@@ -707,10 +726,19 @@ static ssize_t hpd_show(struct device *dev, struct device_attribute *attr, char
}
static DEVICE_ATTR_RO(hpd);
static ssize_t irq_hpd_show(struct device *dev, struct device_attribute *attr, char *buf)
{
struct dp_altmode *dp = dev_get_drvdata(dev);
return sysfs_emit(buf, "%d\n", dp->irq_hpd_count);
}
static DEVICE_ATTR_RO(irq_hpd);
static struct attribute *displayport_attrs[] = {
&dev_attr_configuration.attr,
&dev_attr_pin_assignment.attr,
&dev_attr_hpd.attr,
&dev_attr_irq_hpd.attr,
NULL
};