2021-08-21 08:54:34 +00:00
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From 56212428792d53e5d2c741733d5f284331e84c97 Mon Sep 17 00:00:00 2001
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From: Jonathan Bell <jonathan@raspberrypi.org>
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Date: Tue, 13 Aug 2019 15:53:29 +0100
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Subject: [PATCH] xhci: Use more event ring segment table entries
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Users have reported log spam created by "Event Ring Full" xHC event
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TRBs. These are caused by interrupt latency in conjunction with a very
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busy set of devices on the bus. The errors are benign, but throughput
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will suffer as the xHC will pause processing of transfers until the
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event ring is drained by the kernel. Expand the number of event TRB slots
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available by increasing the number of event ring segments in the ERST.
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Controllers have a hardware-defined limit as to the number of ERST
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entries they can process, so make the actual number in use
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min(ERST_MAX_SEGS, hw_max).
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Signed-off-by: Jonathan Bell <jonathan@raspberrypi.org>
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---
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drivers/usb/host/xhci-mem.c | 8 +++++---
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drivers/usb/host/xhci.h | 4 ++--
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2 files changed, 7 insertions(+), 5 deletions(-)
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--- a/drivers/usb/host/xhci-mem.c
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+++ b/drivers/usb/host/xhci-mem.c
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@@ -2525,9 +2525,11 @@ int xhci_mem_init(struct xhci_hcd *xhci,
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* Event ring setup: Allocate a normal ring, but also setup
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* the event ring segment table (ERST). Section 4.9.3.
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*/
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+ val2 = 1 << HCS_ERST_MAX(xhci->hcs_params2);
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+ val2 = min_t(unsigned int, ERST_MAX_SEGS, val2);
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xhci_dbg_trace(xhci, trace_xhci_dbg_init, "// Allocating event ring");
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- xhci->event_ring = xhci_ring_alloc(xhci, ERST_NUM_SEGS, 1, TYPE_EVENT,
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- 0, flags);
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+ xhci->event_ring = xhci_ring_alloc(xhci, val2, 1, TYPE_EVENT,
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+ 0, flags);
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if (!xhci->event_ring)
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goto fail;
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if (xhci_check_trb_in_td_math(xhci) < 0)
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@@ -2540,7 +2542,7 @@ int xhci_mem_init(struct xhci_hcd *xhci,
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/* set ERST count with the number of entries in the segment table */
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val = readl(&xhci->ir_set->erst_size);
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val &= ERST_SIZE_MASK;
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- val |= ERST_NUM_SEGS;
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+ val |= val2;
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xhci_dbg_trace(xhci, trace_xhci_dbg_init,
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"// Write ERST size = %i to ir_set 0 (some bits preserved)",
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val);
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--- a/drivers/usb/host/xhci.h
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+++ b/drivers/usb/host/xhci.h
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2021-09-12 08:54:32 +00:00
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@@ -1653,8 +1653,8 @@ struct urb_priv {
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2021-08-21 08:54:34 +00:00
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* Each segment table entry is 4*32bits long. 1K seems like an ok size:
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* (1K bytes * 8bytes/bit) / (4*32 bits) = 64 segment entries in the table,
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* meaning 64 ring segments.
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- * Initial allocated size of the ERST, in number of entries */
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-#define ERST_NUM_SEGS 1
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+ * Maximum number of segments in the ERST */
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+#define ERST_MAX_SEGS 8
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/* Initial allocated size of the ERST, in number of entries */
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#define ERST_SIZE 64
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/* Initial number of event segment rings allocated */
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