Hi Mathias,
On 4/30/2024 4:02 AM, Mathias Nyman wrote:
On 26.4.2024 0.50, Wesley Cheng wrote:
Depending on the interrupter use case, the OS may only be used to handle
the interrupter event ring clean up. In these scenarios, event TRBs
don't
need to be handled by the OS, so introduce an xhci interrupter flag to
tag
if the events from an interrupter needs to be handled or not.
Could you elaborate on this a bit.
If I understood correctly the whole point of requesting a secondary xhci
interrupter
for the sideband device without ever requesting a real interrupt for it
was to avoid
waking up the cpu and calling the interrupt handler.
Yes, this is the correct understanding. We don't currently register the
separate interrupt line (from GIC) for the secondary interrupter, so the
main apps proc doesn't get interrupted on events generated on the
secondary interrupter.
with this flag is seems the normal xhci interrupt handler does get
called for
sideband transfer events.
Main intention was to utilize the refactoring you did to expose the
xhci_handle_event_trb() for both handling events on the main
interrupter, as well as the logic to skip events on the secondary
interrupter.
https://lore.kernel.org/linux-usb/44a3d4db-7759-dd93-782a-1efbebfdb22c@xxxxxxxxxxxxxxx/
Signed-off-by: Wesley Cheng <quic_wcheng@xxxxxxxxxxx>
---
drivers/usb/host/xhci-ring.c | 17 +++++++++++++----
drivers/usb/host/xhci.h | 1 +
2 files changed, 14 insertions(+), 4 deletions(-)
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 52278afea94b..6c7a21f522cd 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2973,14 +2973,22 @@ static int handle_tx_event(struct xhci_hcd *xhci,
}
/*
- * This function handles one OS-owned event on the event ring. It may
drop
- * xhci->lock between event processing (e.g. to pass up port status
changes).
+ * This function handles one OS-owned event on the event ring, or
ignores one event
+ * on interrupters which are non-OS owned. It may drop xhci->lock
between event
+ * processing (e.g. to pass up port status changes).
*/
static int xhci_handle_event_trb(struct xhci_hcd *xhci, struct
xhci_interrupter *ir,
union xhci_trb *event)
{
u32 trb_type;
+ /*
+ * Some interrupters do not need to handle event TRBs, as they
may be
+ * managed by another entity, but rely on the OS to clean up.
+ */
+ if (ir->skip_events)
+ return 0;
+
I think we need another solution than a skip_events flag.
To make secondary xhci interrupters more useful in general it would make
more
sense to add an interrupt handler function pointer to struct
xhci_interrupter.
Then call that function instead of xhci_handle_event_trb()
I agree that is how it should be for when support for actually utilizing
secondary interrupters for routing events to different targets (instead
of offloading). However, since I don't have an existing use case that
will exercise this functionality, its a bit difficult to verify that it
should be working the way it was intended.
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -3098,8 +3098,8 @@ static int xhci_handle_events(struct xhci_hcd
*xhci, struct xhci_interrupter *ir
/* Process all OS owned event TRBs on this event ring */
while (unhandled_event_trb(ir->event_ring)) {
- err = xhci_handle_event_trb(xhci, ir,
ir->event_ring->dequeue);
-
+ if (ir->handle_event_trb)
+ err = ir->handle_event_trb(xhci, ir,
ir->event_ring->dequeue);
/*
* If half a segment of events have been handled in one
go then
* update ERDP, and force isoc trbs to interrupt more
often
The handler function would be passed to, and function pointer set in
xhci_create_secondary_interrupter()
For primary interrupter it would always be set to xhci_handle_event_trb()
Yes, definitely agree with this for when we introduce support for
handling the secondary interrupter GIC line within the apps proc itself.
Would prefer if we took up that effort in another series, but willing
to go back to the skip events loop previously implemented if the above
change isn't where you want to go with this.
Thanks
Wesley Cheng
Thanks
Mathias
