6.6-stable review patch. If anyone has any objections, please let me know.
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From: Mathias Nyman mathias.nyman@linux.intel.com
[ Upstream commit cab63934c33b12c0d1e9f4da7450928057f2c142 ]
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: fb18e5bb9660 ("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.... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Stable-dep-of: f3d12ec847b9 ("xhci: dbc: fix bogus 1024 byte prefix if ttyDBC read races with stall event") Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/host/xhci-dbgcap.c | 19 ++++++++++++++++--- drivers/usb/host/xhci-dbgcap.h | 3 +++ 2 files changed, 19 insertions(+), 3 deletions(-)
--- a/drivers/usb/host/xhci-dbgcap.c +++ b/drivers/usb/host/xhci-dbgcap.c @@ -855,6 +855,7 @@ static enum evtreturn xhci_dbc_do_handle { dma_addr_t deq; union xhci_trb *evt; + enum evtreturn ret = EVT_DONE; u32 ctrl, portsc; bool update_erdp = false;
@@ -939,6 +940,7 @@ static enum evtreturn xhci_dbc_do_handle break; case TRB_TYPE(TRB_TRANSFER): dbc_handle_xfer_event(dbc, evt); + ret = EVT_XFER_DONE; break; default: break; @@ -957,7 +959,7 @@ static enum evtreturn xhci_dbc_do_handle lo_hi_writeq(deq, &dbc->regs->erdp); }
- return EVT_DONE; + return ret; }
static void xhci_dbc_handle_events(struct work_struct *work) @@ -966,6 +968,7 @@ static void xhci_dbc_handle_events(struc 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; @@ -984,11 +987,21 @@ static void xhci_dbc_handle_events(struc 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; --- a/drivers/usb/host/xhci-dbgcap.h +++ b/drivers/usb/host/xhci-dbgcap.h @@ -95,6 +95,7 @@ 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: */ @@ -141,6 +142,7 @@ 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];
@@ -186,6 +188,7 @@ struct dbc_request { enum evtreturn { EVT_ERR = -1, EVT_DONE, + EVT_XFER_DONE, EVT_GSER, EVT_DISC, };