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- From 44bfc1e281e081d9ddd0e633ed2dd73c969333f4 Mon Sep 17 00:00:00 2001
- From: Jonathan Bell <[email protected]>
- Date: Tue, 13 Aug 2019 15:53:29 +0100
- Subject: [PATCH] xhci: Use more event ring segment table entries
- Users have reported log spam created by "Event Ring Full" xHC event
- TRBs. These are caused by interrupt latency in conjunction with a very
- busy set of devices on the bus. The errors are benign, but throughput
- will suffer as the xHC will pause processing of transfers until the
- event ring is drained by the kernel. Expand the number of event TRB slots
- available by increasing the number of event ring segments in the ERST.
- Controllers have a hardware-defined limit as to the number of ERST
- entries they can process, so make the actual number in use
- min(ERST_MAX_SEGS, hw_max).
- Signed-off-by: Jonathan Bell <[email protected]>
- ---
- drivers/usb/host/xhci-mem.c | 8 +++++---
- drivers/usb/host/xhci.h | 4 ++--
- 2 files changed, 7 insertions(+), 5 deletions(-)
- --- a/drivers/usb/host/xhci-mem.c
- +++ b/drivers/usb/host/xhci-mem.c
- @@ -2522,9 +2522,11 @@ int xhci_mem_init(struct xhci_hcd *xhci,
- * Event ring setup: Allocate a normal ring, but also setup
- * the event ring segment table (ERST). Section 4.9.3.
- */
- + val2 = 1 << HCS_ERST_MAX(xhci->hcs_params2);
- + val2 = min_t(unsigned int, ERST_MAX_SEGS, val2);
- xhci_dbg_trace(xhci, trace_xhci_dbg_init, "// Allocating event ring");
- - xhci->event_ring = xhci_ring_alloc(xhci, ERST_NUM_SEGS, 1, TYPE_EVENT,
- - 0, flags);
- + xhci->event_ring = xhci_ring_alloc(xhci, val2, 1, TYPE_EVENT,
- + 0, flags);
- if (!xhci->event_ring)
- goto fail;
- if (xhci_check_trb_in_td_math(xhci) < 0)
- @@ -2537,7 +2539,7 @@ int xhci_mem_init(struct xhci_hcd *xhci,
- /* set ERST count with the number of entries in the segment table */
- val = readl(&xhci->ir_set->erst_size);
- val &= ERST_SIZE_MASK;
- - val |= ERST_NUM_SEGS;
- + val |= val2;
- xhci_dbg_trace(xhci, trace_xhci_dbg_init,
- "// Write ERST size = %i to ir_set 0 (some bits preserved)",
- val);
- --- a/drivers/usb/host/xhci.h
- +++ b/drivers/usb/host/xhci.h
- @@ -1672,8 +1672,8 @@ struct urb_priv {
- * Each segment table entry is 4*32bits long. 1K seems like an ok size:
- * (1K bytes * 8bytes/bit) / (4*32 bits) = 64 segment entries in the table,
- * meaning 64 ring segments.
- - * Initial allocated size of the ERST, in number of entries */
- -#define ERST_NUM_SEGS 1
- + * Maximum number of segments in the ERST */
- +#define ERST_MAX_SEGS 8
- /* Poll every 60 seconds */
- #define POLL_TIMEOUT 60
- /* Stop endpoint command timeout (secs) for URB cancellation watchdog timer */
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