From 44bfc1e281e081d9ddd0e633ed2dd73c969333f4 Mon Sep 17 00:00:00 2001 From: Jonathan Bell 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 --- 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 @@ -2524,9 +2524,11 @@ 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) @@ -2539,7 +2541,7 @@ 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 @@ -1677,8 +1677,8 @@ 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 */