[PATCH] Revert "ACPI: EC: Use a spin lock without disabing interrupts"

From: Rafael J. Wysocki
Date: Thu Feb 22 2024 - 04:46:12 EST

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From: "Rafael J. Wysocki" <rafael.j.wysocki@xxxxxxxxx>

Commit eb9299beadbd ("ACPI: EC: Use a spin lock without disabing
interrupts") introduced an unexpected user-visible change in
behavior, which is a significant CPU load increase when the EC
is in use.

This most likely happens due to increased spinlock contention
and so reducing this effect would require a major rework of the
EC driver locking. There is no time for this in the current
cycle, so revert commit eb9299beadbd.

Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218511
Reported-by: Dieter Mummenschanz <dmummenschanz@xxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
---
drivers/acpi/ec.c | 112 +++++++++++++++++++++++++++-------------------
1 file changed, 66 insertions(+), 46 deletions(-)

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index dbdee2924594..02255795b800 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -525,10 +525,12 @@ static void acpi_ec_clear(struct acpi_ec *ec)

static void acpi_ec_enable_event(struct acpi_ec *ec)
{
- spin_lock(&ec->lock);
+ unsigned long flags;
+
+ spin_lock_irqsave(&ec->lock, flags);
if (acpi_ec_started(ec))
__acpi_ec_enable_event(ec);
- spin_unlock(&ec->lock);
+ spin_unlock_irqrestore(&ec->lock, flags);

/* Drain additional events if hardware requires that */
if (EC_FLAGS_CLEAR_ON_RESUME)
@@ -544,9 +546,11 @@ static void __acpi_ec_flush_work(void)

static void acpi_ec_disable_event(struct acpi_ec *ec)
{
- spin_lock(&ec->lock);
+ unsigned long flags;
+
+ spin_lock_irqsave(&ec->lock, flags);
__acpi_ec_disable_event(ec);
- spin_unlock(&ec->lock);
+ spin_unlock_irqrestore(&ec->lock, flags);

/*
* When ec_freeze_events is true, we need to flush events in
@@ -567,9 +571,10 @@ void acpi_ec_flush_work(void)

static bool acpi_ec_guard_event(struct acpi_ec *ec)
{
+ unsigned long flags;
bool guarded;

- spin_lock(&ec->lock);
+ spin_lock_irqsave(&ec->lock, flags);
/*
* If firmware SCI_EVT clearing timing is "event", we actually
* don't know when the SCI_EVT will be cleared by firmware after
@@ -585,29 +590,31 @@ static bool acpi_ec_guard_event(struct acpi_ec *ec)
guarded = ec_event_clearing == ACPI_EC_EVT_TIMING_EVENT &&
ec->event_state != EC_EVENT_READY &&
(!ec->curr || ec->curr->command != ACPI_EC_COMMAND_QUERY);
- spin_unlock(&ec->lock);
+ spin_unlock_irqrestore(&ec->lock, flags);
return guarded;
}

static int ec_transaction_polled(struct acpi_ec *ec)
{
+ unsigned long flags;
int ret = 0;

- spin_lock(&ec->lock);
+ spin_lock_irqsave(&ec->lock, flags);
if (ec->curr && (ec->curr->flags & ACPI_EC_COMMAND_POLL))
ret = 1;
- spin_unlock(&ec->lock);
+ spin_unlock_irqrestore(&ec->lock, flags);
return ret;
}

static int ec_transaction_completed(struct acpi_ec *ec)
{
+ unsigned long flags;
int ret = 0;

- spin_lock(&ec->lock);
+ spin_lock_irqsave(&ec->lock, flags);
if (ec->curr && (ec->curr->flags & ACPI_EC_COMMAND_COMPLETE))
ret = 1;
- spin_unlock(&ec->lock);
+ spin_unlock_irqrestore(&ec->lock, flags);
return ret;
}

@@ -749,6 +756,7 @@ static int ec_guard(struct acpi_ec *ec)

static int ec_poll(struct acpi_ec *ec)
{
+ unsigned long flags;
int repeat = 5; /* number of command restarts */

while (repeat--) {
@@ -757,14 +765,14 @@ static int ec_poll(struct acpi_ec *ec)
do {
if (!ec_guard(ec))
return 0;
- spin_lock(&ec->lock);
+ spin_lock_irqsave(&ec->lock, flags);
advance_transaction(ec, false);
- spin_unlock(&ec->lock);
+ spin_unlock_irqrestore(&ec->lock, flags);
} while (time_before(jiffies, delay));
pr_debug("controller reset, restart transaction\n");
- spin_lock(&ec->lock);
+ spin_lock_irqsave(&ec->lock, flags);
start_transaction(ec);
- spin_unlock(&ec->lock);
+ spin_unlock_irqrestore(&ec->lock, flags);
}
return -ETIME;
}
@@ -772,10 +780,11 @@ static int ec_poll(struct acpi_ec *ec)
static int acpi_ec_transaction_unlocked(struct acpi_ec *ec,
struct transaction *t)
{
+ unsigned long tmp;
int ret = 0;

/* start transaction */
- spin_lock(&ec->lock);
+ spin_lock_irqsave(&ec->lock, tmp);
/* Enable GPE for command processing (IBF=0/OBF=1) */
if (!acpi_ec_submit_flushable_request(ec)) {
ret = -EINVAL;
@@ -786,11 +795,11 @@ static int acpi_ec_transaction_unlocked(struct acpi_ec *ec,
ec->curr = t;
ec_dbg_req("Command(%s) started", acpi_ec_cmd_string(t->command));
start_transaction(ec);
- spin_unlock(&ec->lock);
+ spin_unlock_irqrestore(&ec->lock, tmp);

ret = ec_poll(ec);

- spin_lock(&ec->lock);
+ spin_lock_irqsave(&ec->lock, tmp);
if (t->irq_count == ec_storm_threshold)
acpi_ec_unmask_events(ec);
ec_dbg_req("Command(%s) stopped", acpi_ec_cmd_string(t->command));
@@ -799,7 +808,7 @@ static int acpi_ec_transaction_unlocked(struct acpi_ec *ec,
acpi_ec_complete_request(ec);
ec_dbg_ref(ec, "Decrease command");
unlock:
- spin_unlock(&ec->lock);
+ spin_unlock_irqrestore(&ec->lock, tmp);
return ret;
}

@@ -927,7 +936,9 @@ EXPORT_SYMBOL(ec_get_handle);

static void acpi_ec_start(struct acpi_ec *ec, bool resuming)
{
- spin_lock(&ec->lock);
+ unsigned long flags;
+
+ spin_lock_irqsave(&ec->lock, flags);
if (!test_and_set_bit(EC_FLAGS_STARTED, &ec->flags)) {
ec_dbg_drv("Starting EC");
/* Enable GPE for event processing (SCI_EVT=1) */
@@ -937,28 +948,31 @@ static void acpi_ec_start(struct acpi_ec *ec, bool resuming)
}
ec_log_drv("EC started");
}
- spin_unlock(&ec->lock);
+ spin_unlock_irqrestore(&ec->lock, flags);
}

static bool acpi_ec_stopped(struct acpi_ec *ec)
{
+ unsigned long flags;
bool flushed;

- spin_lock(&ec->lock);
+ spin_lock_irqsave(&ec->lock, flags);
flushed = acpi_ec_flushed(ec);
- spin_unlock(&ec->lock);
+ spin_unlock_irqrestore(&ec->lock, flags);
return flushed;
}

static void acpi_ec_stop(struct acpi_ec *ec, bool suspending)
{
- spin_lock(&ec->lock);
+ unsigned long flags;
+
+ spin_lock_irqsave(&ec->lock, flags);
if (acpi_ec_started(ec)) {
ec_dbg_drv("Stopping EC");
set_bit(EC_FLAGS_STOPPED, &ec->flags);
- spin_unlock(&ec->lock);
+ spin_unlock_irqrestore(&ec->lock, flags);
wait_event(ec->wait, acpi_ec_stopped(ec));
- spin_lock(&ec->lock);
+ spin_lock_irqsave(&ec->lock, flags);
/* Disable GPE for event processing (SCI_EVT=1) */
if (!suspending) {
acpi_ec_complete_request(ec);
@@ -969,25 +983,29 @@ static void acpi_ec_stop(struct acpi_ec *ec, bool suspending)
clear_bit(EC_FLAGS_STOPPED, &ec->flags);
ec_log_drv("EC stopped");
}
- spin_unlock(&ec->lock);
+ spin_unlock_irqrestore(&ec->lock, flags);
}

static void acpi_ec_enter_noirq(struct acpi_ec *ec)
{
- spin_lock(&ec->lock);
+ unsigned long flags;
+
+ spin_lock_irqsave(&ec->lock, flags);
ec->busy_polling = true;
ec->polling_guard = 0;
ec_log_drv("interrupt blocked");
- spin_unlock(&ec->lock);
+ spin_unlock_irqrestore(&ec->lock, flags);
}

static void acpi_ec_leave_noirq(struct acpi_ec *ec)
{
- spin_lock(&ec->lock);
+ unsigned long flags;
+
+ spin_lock_irqsave(&ec->lock, flags);
ec->busy_polling = ec_busy_polling;
ec->polling_guard = ec_polling_guard;
ec_log_drv("interrupt unblocked");
- spin_unlock(&ec->lock);
+ spin_unlock_irqrestore(&ec->lock, flags);
}

void acpi_ec_block_transactions(void)
@@ -1119,9 +1137,9 @@ static void acpi_ec_event_processor(struct work_struct *work)

ec_dbg_evt("Query(0x%02x) stopped", handler->query_bit);

- spin_lock(&ec->lock);
+ spin_lock_irq(&ec->lock);
ec->queries_in_progress--;
- spin_unlock(&ec->lock);
+ spin_unlock_irq(&ec->lock);

acpi_ec_put_query_handler(handler);
kfree(q);
@@ -1184,12 +1202,12 @@ static int acpi_ec_submit_query(struct acpi_ec *ec)
*/
ec_dbg_evt("Query(0x%02x) scheduled", value);

- spin_lock(&ec->lock);
+ spin_lock_irq(&ec->lock);

ec->queries_in_progress++;
queue_work(ec_query_wq, &q->work);

- spin_unlock(&ec->lock);
+ spin_unlock_irq(&ec->lock);

return 0;

@@ -1205,14 +1223,14 @@ static void acpi_ec_event_handler(struct work_struct *work)

ec_dbg_evt("Event started");

- spin_lock(&ec->lock);
+ spin_lock_irq(&ec->lock);

while (ec->events_to_process) {
- spin_unlock(&ec->lock);
+ spin_unlock_irq(&ec->lock);

acpi_ec_submit_query(ec);

- spin_lock(&ec->lock);
+ spin_lock_irq(&ec->lock);

ec->events_to_process--;
}
@@ -1229,11 +1247,11 @@ static void acpi_ec_event_handler(struct work_struct *work)

ec_dbg_evt("Event stopped");

- spin_unlock(&ec->lock);
+ spin_unlock_irq(&ec->lock);

guard_timeout = !!ec_guard(ec);

- spin_lock(&ec->lock);
+ spin_lock_irq(&ec->lock);

/* Take care of SCI_EVT unless someone else is doing that. */
if (guard_timeout && !ec->curr)
@@ -1246,7 +1264,7 @@ static void acpi_ec_event_handler(struct work_struct *work)

ec->events_in_progress--;

- spin_unlock(&ec->lock);
+ spin_unlock_irq(&ec->lock);
}

static void clear_gpe_and_advance_transaction(struct acpi_ec *ec, bool interrupt)
@@ -1271,11 +1289,13 @@ static void clear_gpe_and_advance_transaction(struct acpi_ec *ec, bool interrupt

static void acpi_ec_handle_interrupt(struct acpi_ec *ec)
{
- spin_lock(&ec->lock);
+ unsigned long flags;
+
+ spin_lock_irqsave(&ec->lock, flags);

clear_gpe_and_advance_transaction(ec, true);

- spin_unlock(&ec->lock);
+ spin_unlock_irqrestore(&ec->lock, flags);
}

static u32 acpi_ec_gpe_handler(acpi_handle gpe_device,
@@ -2085,7 +2105,7 @@ bool acpi_ec_dispatch_gpe(void)
* Dispatch the EC GPE in-band, but do not report wakeup in any case
* to allow the caller to process events properly after that.
*/
- spin_lock(&first_ec->lock);
+ spin_lock_irq(&first_ec->lock);

if (acpi_ec_gpe_status_set(first_ec)) {
pm_pr_dbg("ACPI EC GPE status set\n");
@@ -2094,7 +2114,7 @@ bool acpi_ec_dispatch_gpe(void)
work_in_progress = acpi_ec_work_in_progress(first_ec);
}

- spin_unlock(&first_ec->lock);
+ spin_unlock_irq(&first_ec->lock);

if (!work_in_progress)
return false;
@@ -2107,11 +2127,11 @@ bool acpi_ec_dispatch_gpe(void)

pm_pr_dbg("ACPI EC work flushed\n");

- spin_lock(&first_ec->lock);
+ spin_lock_irq(&first_ec->lock);

work_in_progress = acpi_ec_work_in_progress(first_ec);

- spin_unlock(&first_ec->lock);
+ spin_unlock_irq(&first_ec->lock);
} while (work_in_progress && !pm_wakeup_pending());

return false;
--
2.35.3

Next message: Rob Herring: "Re: [PATCH v2 1/2] ASoC: dt-bindings: Added schema for "nuvoton,nau8325""
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