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UPSTREAM: xhci: dbc: Avoid event polling busyloop if pending rx transfers are inactive.

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Event polling delay is set to 0 if there are any pending requests in
either rx or tx requests lists. Checking for pending requests does
not work well for "IN" transfers as the tty driver always queues
requests to the list and TRBs to the ring, preparing to receive data
from the host.

This causes unnecessary busylooping and cpu hogging.

Only set the event polling delay to 0 if there are pending tx "write"
transfers, or if it was less than 10ms since last active data transfer
in any direction.

Cc: Łukasz Bartosik <ukaszb@chromium.org>
Fixes: fb18e5bb96 ("xhci: dbc: poll at different rate depending on data transfer activity")
Cc: stable@vger.kernel.org
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20250505125630.561699-3-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit cab63934c33b12c0d1e9f4da7450928057f2c142)

Bug: None
Test: None
Change-Id: Iee426995a6a4009311d46bd93d4ab4d5f590dedb
Signed-off-by: Łukasz Bartosik <ukaszb@google.com>
This commit is contained in:
Mathias Nyman
2025-05-05 15:56:30 +03:00
committed by Treehugger Robot
parent 5db5b73d80
commit d3e9951ff1
2 changed files with 19 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

19
drivers/usb/host/xhci-dbgcap.c
View File

@@ -822,6 +822,7 @@ static enum evtreturn xhci_dbc_do_handle_events(struct xhci_dbc *dbc)
{
dma_addr_t deq;
union xhci_trb *evt;
enum evtreturn ret = EVT_DONE;
u32 ctrl, portsc;
bool update_erdp = false;
@@ -906,6 +907,7 @@ static enum evtreturn xhci_dbc_do_handle_events(struct xhci_dbc *dbc)
break;
case TRB_TYPE(TRB_TRANSFER):
dbc_handle_xfer_event(dbc, evt);
ret = EVT_XFER_DONE;
break;
default:
break;
@@ -924,7 +926,7 @@ static enum evtreturn xhci_dbc_do_handle_events(struct xhci_dbc *dbc)
lo_hi_writeq(deq, &dbc->regs->erdp);
}
return EVT_DONE;
return ret;
}
static void xhci_dbc_handle_events(struct work_struct *work)
@@ -933,6 +935,7 @@ static void xhci_dbc_handle_events(struct work_struct *work)
struct xhci_dbc *dbc;
unsigned long flags;
unsigned int poll_interval;
unsigned long busypoll_timelimit;
dbc = container_of(to_delayed_work(work), struct xhci_dbc, event_work);
poll_interval = dbc->poll_interval;
@@ -951,11 +954,21 @@ static void xhci_dbc_handle_events(struct work_struct *work)
dbc->driver->disconnect(dbc);
break;
case EVT_DONE:
/* set fast poll rate if there are pending data transfers */
/*
* Set fast poll rate if there are pending out transfers, or
* a transfer was recently processed
*/
busypoll_timelimit = dbc->xfer_timestamp +
msecs_to_jiffies(DBC_XFER_INACTIVITY_TIMEOUT);
if (!list_empty(&dbc->eps[BULK_OUT].list_pending) ||
!list_empty(&dbc->eps[BULK_IN].list_pending))
time_is_after_jiffies(busypoll_timelimit))
poll_interval = 0;
break;
case EVT_XFER_DONE:
dbc->xfer_timestamp = jiffies;
poll_interval = 0;
break;
default:
dev_info(dbc->dev, "stop handling dbc events\n");
return;

3
drivers/usb/host/xhci-dbgcap.h
View File

@@ -96,6 +96,7 @@ struct dbc_ep {
#define DBC_WRITE_BUF_SIZE 8192
#define DBC_POLL_INTERVAL_DEFAULT 64 /* milliseconds */
#define DBC_POLL_INTERVAL_MAX 5000 /* milliseconds */
#define DBC_XFER_INACTIVITY_TIMEOUT 10 /* milliseconds */
/*
* Private structure for DbC hardware state:
*/
@@ -142,6 +143,7 @@ struct xhci_dbc {
enum dbc_state state;
struct delayed_work event_work;
unsigned int poll_interval; /* ms */
unsigned long xfer_timestamp;
unsigned resume_required:1;
struct dbc_ep eps[2];
@@ -187,6 +189,7 @@ struct dbc_request {
enum evtreturn {
EVT_ERR = -1,
EVT_DONE,
EVT_XFER_DONE,
EVT_GSER,
EVT_DISC,
};