firewire: core: allocate workqueue to handle isochronous contexts in card

This commit adds a workqueue dedicated for isochronous context processing.

The workqueue is allocated per instance of fw_card structure to satisfy the
following characteristics descending from 1394 OHCI specification:

In 1394 OHCI specification, memory pages are reserved to each isochronous
context dedicated to DMA transmission. It allows to operate these
per-context pages concurrently. Software can schedule hardware interrupt
for several isochronous context to the same cycle, thus WQ_UNBOUND is
specified. Additionally, it is sleepable to operate the content of pages,
thus WQ_BH is not used.

The isochronous context delivers the packets with time stamp, thus
WQ_HIGHPRI is specified for semi real-time data such as IEC 61883-1/6
protocol implemented by ALSA firewire stack. The isochronous context is not
used by the implementation of SCSI over IEEE1394 protocol (sbp2), thus
WQ_MEM_RECLAIM is not specified.

It is useful for users to adjust cpu affinity of the workqueue depending
on their work loads, thus WQ_SYS is specified to expose the attributes to
user space.

Tested-by: Edmund Raile <edmund.raile@protonmail.com>
Link: https://lore.kernel.org/r/20240904125155.461886-2-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>

diff --git a/drivers/firewire/core-card.c b/drivers/firewire/core-card.c
index e80b762888fa13d176b74e362e0b3816d557ac51..01354b9de8b23612789c208d717f7964af5f47b0 100644 (file)
--- a/drivers/firewire/core-card.c
+++ b/drivers/firewire/core-card.c
@@ -571,11 +571,30 @@ void fw_card_initialize(struct fw_card *card,
 }
 EXPORT_SYMBOL(fw_card_initialize);
 
-int fw_card_add(struct fw_card *card,
-               u32 max_receive, u32 link_speed, u64 guid)
+int fw_card_add(struct fw_card *card, u32 max_receive, u32 link_speed, u64 guid,
+               unsigned int supported_isoc_contexts)
 {
+       struct workqueue_struct *isoc_wq;
        int ret;
 
+       // This workqueue should be:
+       //  * != WQ_BH                  Sleepable.
+       //  * == WQ_UNBOUND             Any core can process data for isoc context. The
+       //                              implementation of unit protocol could consumes the core
+       //                              longer somehow.
+       //  * != WQ_MEM_RECLAIM         Not used for any backend of block device.
+       //  * == WQ_FREEZABLE           Isochronous communication is at regular interval in real
+       //                              time, thus should be drained if possible at freeze phase.
+       //  * == WQ_HIGHPRI             High priority to process semi-realtime timestamped data.
+       //  * == WQ_SYSFS               Parameters are available via sysfs.
+       //  * max_active == n_it + n_ir A hardIRQ could notify events for multiple isochronous
+       //                              contexts if they are scheduled to the same cycle.
+       isoc_wq = alloc_workqueue("firewire-isoc-card%u",
+                                 WQ_UNBOUND | WQ_FREEZABLE | WQ_HIGHPRI | WQ_SYSFS,
+                                 supported_isoc_contexts, card->index);
+       if (!isoc_wq)
+               return -ENOMEM;
+
        card->max_receive = max_receive;
        card->link_speed = link_speed;
        card->guid = guid;
@@ -584,9 +603,12 @@ int fw_card_add(struct fw_card *card,
 
        generate_config_rom(card, tmp_config_rom);
        ret = card->driver->enable(card, tmp_config_rom, config_rom_length);
-       if (ret < 0)
+       if (ret < 0) {
+               destroy_workqueue(isoc_wq);
                return ret;
+       }
 
+       card->isoc_wq = isoc_wq;
        list_add_tail(&card->link, &card_list);
 
        return 0;
@@ -708,6 +730,8 @@ void fw_core_remove_card(struct fw_card *card)
 {
        struct fw_card_driver dummy_driver = dummy_driver_template;
 
+       might_sleep();
+
        card->driver->update_phy_reg(card, 4,
                                     PHY_LINK_ACTIVE | PHY_CONTENDER, 0);
        fw_schedule_bus_reset(card, false, true);
@@ -719,6 +743,7 @@ void fw_core_remove_card(struct fw_card *card)
        dummy_driver.free_iso_context   = card->driver->free_iso_context;
        dummy_driver.stop_iso           = card->driver->stop_iso;
        card->driver = &dummy_driver;
+       drain_workqueue(card->isoc_wq);
 
        scoped_guard(spinlock_irqsave, &card->lock)
                fw_destroy_nodes(card);
@@ -727,6 +752,8 @@ void fw_core_remove_card(struct fw_card *card)
        fw_card_put(card);
        wait_for_completion(&card->done);
 
+       destroy_workqueue(card->isoc_wq);
+
        WARN_ON(!list_empty(&card->transaction_list));
 }
 EXPORT_SYMBOL(fw_core_remove_card);

diff --git a/drivers/firewire/core.h b/drivers/firewire/core.h
index 57d101c01e36eeb11a9aa4b0f61c05c54bec571d..96ae366889e0e27fb51d3440fbea7b993d72bf5a 100644 (file)
--- a/drivers/firewire/core.h
+++ b/drivers/firewire/core.h
@@ -115,8 +115,8 @@ struct fw_card_driver {
 
 void fw_card_initialize(struct fw_card *card,
                const struct fw_card_driver *driver, struct device *device);
-int fw_card_add(struct fw_card *card,
-               u32 max_receive, u32 link_speed, u64 guid);
+int fw_card_add(struct fw_card *card, u32 max_receive, u32 link_speed, u64 guid,
+               unsigned int supported_isoc_contexts);
 void fw_core_remove_card(struct fw_card *card);
 int fw_compute_block_crc(__be32 *block);
 void fw_schedule_bm_work(struct fw_card *card, unsigned long delay);

diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c
index 3930fdd561552cf6add7ffa4a5233c909fd3883d..50627b8fc38f7c1284b3b1c1f2f78b5cad3be598 100644 (file)
--- a/drivers/firewire/ohci.c
+++ b/drivers/firewire/ohci.c
@@ -3827,7 +3827,7 @@ static int pci_probe(struct pci_dev *dev,
                goto fail_msi;
        }
 
-       err = fw_card_add(&ohci->card, max_receive, link_speed, guid);
+       err = fw_card_add(&ohci->card, max_receive, link_speed, guid, ohci->n_it + ohci->n_ir);
        if (err)
                goto fail_irq;
 

diff --git a/include/linux/firewire.h b/include/linux/firewire.h
index 1cca14cf56527be1d1e4f45d8ccfae8a86c66a7a..10e135d6082412a6c7e82309f5fb09d3bf9a26ac 100644 (file)
--- a/include/linux/firewire.h
+++ b/include/linux/firewire.h
@@ -134,6 +134,8 @@ struct fw_card {
        __be32 topology_map[(CSR_TOPOLOGY_MAP_END - CSR_TOPOLOGY_MAP) / 4];
 
        __be32 maint_utility_register;
+
+       struct workqueue_struct *isoc_wq;
 };
 
 static inline struct fw_card *fw_card_get(struct fw_card *card)