From 4352b8aee98005853aa63f57d6377282de17a33f Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 23 Aug 2026 13:28:57 -0700 Subject: Merge tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linux Pull I3C updates from Alexandre Belloni: "A new driver this cycle, for the AMD AXI I3C controller. There are also new features such as IBI wakeup support, SETAASA device discovery and ACPI support for the the DAA methods, meaning we can now communicate with the SPD devices on DDR5 modules. New driver: - AMD AXI I3C master controller Subsystem: - I3C Common Command Code (CCC) handling improvements, especially around GET CCCs - SETAASA device discovery support - ACPI support for all existing DAA methods like SETDASA, SETNEWDA as well as I2C devices on I3C bus - IBI-based wakeup support Drivers: - dw: SETAASA support - mipi-i3c-hci: advertise IBI wakeup capability, AMD_PT I3C controller support, PIO queue management support for HCI v1.2 - renesas: improve suspend to RAM support, add runtime PM support" * tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linux: (70 commits) i3c: dw: reduce do_daa time if there's no client i3c: mipi-i3c-hci: Add support for AMD_PT I3C controller i3c: mipi-i3c-hci: Add PIO queue management support for HCI v1.2 i3c: mipi-i3c-hci: Fix missing STAT_IBI_STATUS_THLD in PIO mode i3c: dw: rename "pclk" to "apb" to match dt-binding i3c: dw: make struct dw_i3c_cmd smaller i3c: dw: use COMMAND_PORT_TRANSFER_ARG instead of hardcoding i3c: renesas: Don't register devices when ENTDAA times out i3c: master: dw-i3c-master: fix OD timing for first broadcast i3c: mipi-i3c-hci: Advertise IBI wakeup capability i3c: mipi-i3c-hci: Factor out i3c_hci_sysdev() i3c: mipi-i3c-hci-pci: Propagate I3C wakeup requirements to PCI i3c: master: Reject IBI requests from non-IBI-capable devices i3c: master: Add helper to query bus wakeup requirements i3c: master: Report wakeup events for IBIs i3c: master: Support IBI-based wakeup capability i3c: master: Fix potential UAF in i3c_device_match() i3c: master: Fix potential UAF in i3c_device_uevent() i3c: Make dev->desc locking assumptions explicit i3c: master: Fix use-after-free of master->this ... --- lib/dynamic_queue_limits.c | 217 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 217 insertions(+) create mode 100644 lib/dynamic_queue_limits.c (limited to 'lib/dynamic_queue_limits.c') diff --git a/lib/dynamic_queue_limits.c b/lib/dynamic_queue_limits.c new file mode 100644 index 000000000..f97a752e9 --- /dev/null +++ b/lib/dynamic_queue_limits.c @@ -0,0 +1,217 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Dynamic byte queue limits. See include/linux/dynamic_queue_limits.h + * + * Copyright (c) 2011, Tom Herbert + */ +#include +#include +#include +#include +#include +#include +#include + +#define POSDIFF(A, B) ((int)((A) - (B)) > 0 ? (A) - (B) : 0) +#define AFTER_EQ(A, B) ((int)((A) - (B)) >= 0) + +static void dql_check_stall(struct dql *dql, unsigned short stall_thrs) +{ + unsigned long now; + + if (!stall_thrs) + return; + + now = jiffies; + /* Check for a potential stall */ + if (time_after_eq(now, dql->last_reap + stall_thrs)) { + unsigned long hist_head, t, start, end; + + /* We are trying to detect a period of at least @stall_thrs + * jiffies without any Tx completions, but during first half + * of which some Tx was posted. + */ +dqs_again: + hist_head = READ_ONCE(dql->history_head); + /* pairs with smp_wmb() in dql_queued() */ + smp_rmb(); + + /* Get the previous entry in the ring buffer, which is the + * oldest sample. + */ + start = (hist_head - DQL_HIST_LEN + 1) * BITS_PER_LONG; + + /* Advance start to continue from the last reap time */ + if (time_before(start, dql->last_reap + 1)) + start = dql->last_reap + 1; + + /* Newest sample we should have already seen a completion for */ + end = hist_head * BITS_PER_LONG + (BITS_PER_LONG - 1); + + /* Shrink the search space to [start, (now - start_thrs/2)] if + * `end` is beyond the stall zone + */ + if (time_before(now, end + stall_thrs / 2)) + end = now - stall_thrs / 2; + + /* Search for the queued time in [t, end] */ + for (t = start; time_before_eq(t, end); t++) + if (test_bit(t % (DQL_HIST_LEN * BITS_PER_LONG), + dql->history)) + break; + + /* Variable t contains the time of the queue */ + if (!time_before_eq(t, end)) + goto no_stall; + + /* The ring buffer was modified in the meantime, retry */ + if (hist_head != READ_ONCE(dql->history_head)) + goto dqs_again; + + dql->stall_cnt++; + dql->stall_max = max_t(unsigned short, dql->stall_max, now - t); + + trace_dql_stall_detected(dql->stall_thrs, now - t, + dql->last_reap, dql->history_head, + now, dql->history); + } +no_stall: + dql->last_reap = now; +} + +/* Records completed count and recalculates the queue limit */ +void dql_completed(struct dql *dql, unsigned int count) +{ + unsigned int inprogress, prev_inprogress, limit; + unsigned int ovlimit, completed, num_queued; + unsigned short stall_thrs; + bool all_prev_completed; + + num_queued = READ_ONCE(dql->num_queued); + /* Read stall_thrs in advance since it belongs to the same (first) + * cache line as ->num_queued. This way, dql_check_stall() does not + * need to touch the first cache line again later, reducing the window + * of possible false sharing. + */ + stall_thrs = READ_ONCE(dql->stall_thrs); + + /* Can't complete more than what's in queue */ + BUG_ON(count > num_queued - dql->num_completed); + + completed = dql->num_completed + count; + limit = dql->limit; + ovlimit = POSDIFF(num_queued - dql->num_completed, limit); + inprogress = num_queued - completed; + prev_inprogress = dql->prev_num_queued - dql->num_completed; + all_prev_completed = AFTER_EQ(completed, dql->prev_num_queued); + + if ((ovlimit && !inprogress) || + (dql->prev_ovlimit && all_prev_completed)) { + /* + * Queue considered starved if: + * - The queue was over-limit in the last interval, + * and there is no more data in the queue. + * OR + * - The queue was over-limit in the previous interval and + * when enqueuing it was possible that all queued data + * had been consumed. This covers the case when queue + * may have becomes starved between completion processing + * running and next time enqueue was scheduled. + * + * When queue is starved increase the limit by the amount + * of bytes both sent and completed in the last interval, + * plus any previous over-limit. + */ + limit += POSDIFF(completed, dql->prev_num_queued) + + dql->prev_ovlimit; + dql->slack_start_time = jiffies; + dql->lowest_slack = UINT_MAX; + } else if (inprogress && prev_inprogress && !all_prev_completed) { + /* + * Queue was not starved, check if the limit can be decreased. + * A decrease is only considered if the queue has been busy in + * the whole interval (the check above). + * + * If there is slack, the amount of excess data queued above + * the amount needed to prevent starvation, the queue limit + * can be decreased. To avoid hysteresis we consider the + * minimum amount of slack found over several iterations of the + * completion routine. + */ + unsigned int slack, slack_last_objs; + + /* + * Slack is the maximum of + * - The queue limit plus previous over-limit minus twice + * the number of objects completed. Note that two times + * number of completed bytes is a basis for an upper bound + * of the limit. + * - Portion of objects in the last queuing operation that + * was not part of non-zero previous over-limit. That is + * "round down" by non-overlimit portion of the last + * queueing operation. + */ + slack = POSDIFF(limit + dql->prev_ovlimit, + 2 * (completed - dql->num_completed)); + slack_last_objs = dql->prev_ovlimit ? + POSDIFF(dql->prev_last_obj_cnt, dql->prev_ovlimit) : 0; + + slack = max(slack, slack_last_objs); + + if (slack < dql->lowest_slack) + dql->lowest_slack = slack; + + if (time_after(jiffies, + dql->slack_start_time + dql->slack_hold_time)) { + limit = POSDIFF(limit, dql->lowest_slack); + dql->slack_start_time = jiffies; + dql->lowest_slack = UINT_MAX; + } + } + + /* Enforce bounds on limit */ + limit = clamp(limit, dql->min_limit, dql->max_limit); + + if (limit != dql->limit) { + dql->limit = limit; + ovlimit = 0; + } + + dql->adj_limit = limit + completed; + dql->prev_ovlimit = ovlimit; + dql->prev_last_obj_cnt = READ_ONCE(dql->last_obj_cnt); + dql->num_completed = completed; + dql->prev_num_queued = num_queued; + + dql_check_stall(dql, stall_thrs); +} +EXPORT_SYMBOL(dql_completed); + +void dql_reset(struct dql *dql) +{ + /* Reset all dynamic values */ + dql->limit = dql->min_limit; + dql->num_queued = 0; + dql->num_completed = 0; + dql->last_obj_cnt = 0; + dql->prev_num_queued = 0; + dql->prev_last_obj_cnt = 0; + dql->prev_ovlimit = 0; + dql->lowest_slack = UINT_MAX; + dql->slack_start_time = jiffies; + + dql->last_reap = jiffies; + dql->history_head = jiffies / BITS_PER_LONG; + memset(dql->history, 0, sizeof(dql->history)); +} +EXPORT_SYMBOL(dql_reset); + +void dql_init(struct dql *dql, unsigned int hold_time) +{ + dql->max_limit = DQL_MAX_LIMIT; + dql->min_limit = 0; + dql->slack_hold_time = hold_time; + dql->stall_thrs = 0; + dql_reset(dql); +} +EXPORT_SYMBOL(dql_init); -- cgit v1.3.1