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Message-ID: <20250915234747.915922-6-o-takashi@sakamocchi.jp>
Date: Tue, 16 Sep 2025 08:47:46 +0900
From: Takashi Sakamoto <o-takashi@...amocchi.jp>
To: linux1394-devel@...ts.sourceforge.net
Cc: linux-kernel@...r.kernel.org
Subject: [PATCH 5/6] firewire: core: use spin lock specific to timer for split transaction
At present the parameters to compute timeout time for split transaction is
protected by card-wide spin lock, while it is not necessarily convenient
in a point to narrower critical section.
This commit adds and uses another spin lock specific for the purpose.
Signed-off-by: Takashi Sakamoto <o-takashi@...amocchi.jp>
---
drivers/firewire/core-card.c | 10 +++--
drivers/firewire/core-transaction.c | 63 +++++++++++++++++++----------
include/linux/firewire.h | 15 ++++---
3 files changed, 57 insertions(+), 31 deletions(-)
diff --git a/drivers/firewire/core-card.c b/drivers/firewire/core-card.c
index 39f95007305f..96495392a1f6 100644
--- a/drivers/firewire/core-card.c
+++ b/drivers/firewire/core-card.c
@@ -550,10 +550,12 @@ void fw_card_initialize(struct fw_card *card,
INIT_LIST_HEAD(&card->transactions.list);
spin_lock_init(&card->transactions.lock);
- card->split_timeout_hi = DEFAULT_SPLIT_TIMEOUT / 8000;
- card->split_timeout_lo = (DEFAULT_SPLIT_TIMEOUT % 8000) << 19;
- card->split_timeout_cycles = DEFAULT_SPLIT_TIMEOUT;
- card->split_timeout_jiffies = isoc_cycles_to_jiffies(DEFAULT_SPLIT_TIMEOUT);
+ card->split_timeout.hi = DEFAULT_SPLIT_TIMEOUT / 8000;
+ card->split_timeout.lo = (DEFAULT_SPLIT_TIMEOUT % 8000) << 19;
+ card->split_timeout.cycles = DEFAULT_SPLIT_TIMEOUT;
+ card->split_timeout.jiffies = isoc_cycles_to_jiffies(DEFAULT_SPLIT_TIMEOUT);
+ spin_lock_init(&card->split_timeout.lock);
+
card->color = 0;
card->broadcast_channel = BROADCAST_CHANNEL_INITIAL;
diff --git a/drivers/firewire/core-transaction.c b/drivers/firewire/core-transaction.c
index 5366d8a781ac..dd3656a0c1ff 100644
--- a/drivers/firewire/core-transaction.c
+++ b/drivers/firewire/core-transaction.c
@@ -137,14 +137,18 @@ static void split_transaction_timeout_callback(struct timer_list *timer)
static void start_split_transaction_timeout(struct fw_transaction *t,
struct fw_card *card)
{
- guard(spinlock_irqsave)(&card->lock);
+ unsigned long delta;
if (list_empty(&t->link) || WARN_ON(t->is_split_transaction))
return;
t->is_split_transaction = true;
- mod_timer(&t->split_timeout_timer,
- jiffies + card->split_timeout_jiffies);
+
+ // NOTE: This can be without irqsave when we can guarantee that __fw_send_request() for
+ // local destination never runs in any type of IRQ context.
+ scoped_guard(spinlock_irqsave, &card->split_timeout.lock)
+ delta = card->split_timeout.jiffies;
+ mod_timer(&t->split_timeout_timer, jiffies + delta);
}
static u32 compute_split_timeout_timestamp(struct fw_card *card, u32 request_timestamp);
@@ -164,8 +168,12 @@ static void transmit_complete_callback(struct fw_packet *packet,
break;
case ACK_PENDING:
{
- t->split_timeout_cycle =
- compute_split_timeout_timestamp(card, packet->timestamp) & 0xffff;
+ // NOTE: This can be without irqsave when we can guarantee that __fw_send_request() for
+ // local destination never runs in any type of IRQ context.
+ scoped_guard(spinlock_irqsave, &card->split_timeout.lock) {
+ t->split_timeout_cycle =
+ compute_split_timeout_timestamp(card, packet->timestamp) & 0xffff;
+ }
start_split_transaction_timeout(t, card);
break;
}
@@ -790,11 +798,14 @@ EXPORT_SYMBOL(fw_fill_response);
static u32 compute_split_timeout_timestamp(struct fw_card *card,
u32 request_timestamp)
+__must_hold(&card->split_timeout.lock)
{
unsigned int cycles;
u32 timestamp;
- cycles = card->split_timeout_cycles;
+ lockdep_assert_held(&card->split_timeout.lock);
+
+ cycles = card->split_timeout.cycles;
cycles += request_timestamp & 0x1fff;
timestamp = request_timestamp & ~0x1fff;
@@ -845,9 +856,12 @@ static struct fw_request *allocate_request(struct fw_card *card,
return NULL;
kref_init(&request->kref);
+ // NOTE: This can be without irqsave when we can guarantee that __fw_send_request() for
+ // local destination never runs in any type of IRQ context.
+ scoped_guard(spinlock_irqsave, &card->split_timeout.lock)
+ request->response.timestamp = compute_split_timeout_timestamp(card, p->timestamp);
+
request->response.speed = p->speed;
- request->response.timestamp =
- compute_split_timeout_timestamp(card, p->timestamp);
request->response.generation = p->generation;
request->response.ack = 0;
request->response.callback = free_response_callback;
@@ -1228,16 +1242,17 @@ static const struct fw_address_region registers_region =
.end = CSR_REGISTER_BASE | CSR_CONFIG_ROM, };
static void update_split_timeout(struct fw_card *card)
+__must_hold(&card->split_timeout.lock)
{
unsigned int cycles;
- cycles = card->split_timeout_hi * 8000 + (card->split_timeout_lo >> 19);
+ cycles = card->split_timeout.hi * 8000 + (card->split_timeout.lo >> 19);
/* minimum per IEEE 1394, maximum which doesn't overflow OHCI */
cycles = clamp(cycles, 800u, 3u * 8000u);
- card->split_timeout_cycles = cycles;
- card->split_timeout_jiffies = isoc_cycles_to_jiffies(cycles);
+ card->split_timeout.cycles = cycles;
+ card->split_timeout.jiffies = isoc_cycles_to_jiffies(cycles);
}
static void handle_registers(struct fw_card *card, struct fw_request *request,
@@ -1287,12 +1302,15 @@ static void handle_registers(struct fw_card *card, struct fw_request *request,
case CSR_SPLIT_TIMEOUT_HI:
if (tcode == TCODE_READ_QUADLET_REQUEST) {
- *data = cpu_to_be32(card->split_timeout_hi);
+ *data = cpu_to_be32(card->split_timeout.hi);
} else if (tcode == TCODE_WRITE_QUADLET_REQUEST) {
- guard(spinlock_irqsave)(&card->lock);
-
- card->split_timeout_hi = be32_to_cpu(*data) & 7;
- update_split_timeout(card);
+ // NOTE: This can be without irqsave when we can guarantee that
+ // __fw_send_request() for local destination never runs in any type of IRQ
+ // context.
+ scoped_guard(spinlock_irqsave, &card->split_timeout.lock) {
+ card->split_timeout.hi = be32_to_cpu(*data) & 7;
+ update_split_timeout(card);
+ }
} else {
rcode = RCODE_TYPE_ERROR;
}
@@ -1300,12 +1318,15 @@ static void handle_registers(struct fw_card *card, struct fw_request *request,
case CSR_SPLIT_TIMEOUT_LO:
if (tcode == TCODE_READ_QUADLET_REQUEST) {
- *data = cpu_to_be32(card->split_timeout_lo);
+ *data = cpu_to_be32(card->split_timeout.lo);
} else if (tcode == TCODE_WRITE_QUADLET_REQUEST) {
- guard(spinlock_irqsave)(&card->lock);
-
- card->split_timeout_lo = be32_to_cpu(*data) & 0xfff80000;
- update_split_timeout(card);
+ // NOTE: This can be without irqsave when we can guarantee that
+ // __fw_send_request() for local destination never runs in any type of IRQ
+ // context.
+ scoped_guard(spinlock_irqsave, &card->split_timeout.lock) {
+ card->split_timeout.lo = be32_to_cpu(*data) & 0xfff80000;
+ update_split_timeout(card);
+ }
} else {
rcode = RCODE_TYPE_ERROR;
}
diff --git a/include/linux/firewire.h b/include/linux/firewire.h
index 8d6801cf2fca..6d208769d456 100644
--- a/include/linux/firewire.h
+++ b/include/linux/firewire.h
@@ -97,18 +97,21 @@ struct fw_card {
spinlock_t lock;
} transactions;
- u32 split_timeout_hi;
- u32 split_timeout_lo;
- unsigned int split_timeout_cycles;
- unsigned int split_timeout_jiffies;
+ struct {
+ u32 hi;
+ u32 lo;
+ unsigned int cycles;
+ unsigned int jiffies;
+ spinlock_t lock;
+ } split_timeout;
unsigned long long guid;
unsigned max_receive;
int link_speed;
int config_rom_generation;
- spinlock_t lock; /* Take this lock when handling the lists in
- * this struct. */
+ spinlock_t lock;
+
struct fw_node *local_node;
struct fw_node *root_node;
struct fw_node *irm_node;
--
2.48.1
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