firewire: core: move workqueue handler from 1394 OHCI driver to core function

In current implementation, the work item for isochronous context executes
the same procedure of fw_iso_context_flush_completions() internally. There
is a space to refactor the implementation.

This commit calls fw_iso_context_flush_completions() in the work item. It
obsoletes fw_iso_context_init_work(). It also obsoletes a pair of
disable_work_sync() and enable_work() since the usage of
test_and_set_bit_lock() mediates concurrent call already.

Link: https://lore.kernel.org/r/20240909140018.65289-2-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>

drivers/firewire/core-iso.c

@@ -131,6 +131,13 @@ size_t fw_iso_buffer_lookup(struct fw_iso_buffer *buffer, dma_addr_t completed)
 	return 0;
 }
 
+static void flush_completions_work(struct work_struct *work)
+{
+	struct fw_iso_context *ctx = container_of(work, struct fw_iso_context, work);
+
+	fw_iso_context_flush_completions(ctx);
+}
+
 struct fw_iso_context *fw_iso_context_create(struct fw_card *card,
 		int type, int channel, int speed, size_t header_size,
 		fw_iso_callback_t callback, void *callback_data)
@@ -149,6 +156,7 @@ struct fw_iso_context *fw_iso_context_create(struct fw_card *card,
 	ctx->header_size = header_size;
 	ctx->callback.sc = callback;
 	ctx->callback_data = callback_data;
+	INIT_WORK(&ctx->work, flush_completions_work);
 
 	trace_isoc_outbound_allocate(ctx, channel, speed);
 	trace_isoc_inbound_single_allocate(ctx, channel, header_size);
@@ -218,29 +226,15 @@ EXPORT_SYMBOL(fw_iso_context_queue_flush);
  * to process the context asynchronously, fw_iso_context_schedule_flush_completions() is available
  * instead.
  *
- * Context: Process context. May sleep due to disable_work_sync().
+ * Context: Process context.
  */
 int fw_iso_context_flush_completions(struct fw_iso_context *ctx)
 {
-	int err;
-
 	trace_isoc_outbound_flush_completions(ctx);
 	trace_isoc_inbound_single_flush_completions(ctx);
 	trace_isoc_inbound_multiple_flush_completions(ctx);
 
-	might_sleep();
+	return ctx->card->driver->flush_iso_completions(ctx);
-
-	// Avoid dead lock due to programming mistake.
-	if (WARN_ON_ONCE(current_work() == &ctx->work))
-		return 0;
-
-	disable_work_sync(&ctx->work);
-
-	err = ctx->card->driver->flush_iso_completions(ctx);
-
-	enable_work(&ctx->work);
-
-	return err;
 }
 EXPORT_SYMBOL(fw_iso_context_flush_completions);
 

drivers/firewire/core.h

@@ -159,11 +159,6 @@ int fw_iso_buffer_alloc(struct fw_iso_buffer *buffer, int page_count);
 int fw_iso_buffer_map_dma(struct fw_iso_buffer *buffer, struct fw_card *card,
 			  enum dma_data_direction direction);
 
-static inline void fw_iso_context_init_work(struct fw_iso_context *ctx, work_func_t func)
-{
-	INIT_WORK(&ctx->work, func);
-}
-
 
 /* -topology */
 

drivers/firewire/ohci.c

@@ -1182,47 +1182,6 @@ static void context_tasklet(unsigned long data)
 	}
 }
 
-static void ohci_isoc_context_work(struct work_struct *work)
-{
-	struct fw_iso_context *base = container_of(work, struct fw_iso_context, work);
-	struct iso_context *isoc_ctx = container_of(base, struct iso_context, base);
-	struct context *ctx = &isoc_ctx->context;
-	struct descriptor *d, *last;
-	u32 address;
-	int z;
-	struct descriptor_buffer *desc;
-
-	desc = list_entry(ctx->buffer_list.next, struct descriptor_buffer, list);
-	last = ctx->last;
-	while (last->branch_address != 0) {
-		struct descriptor_buffer *old_desc = desc;
-
-		address = le32_to_cpu(last->branch_address);
-		z = address & 0xf;
-		address &= ~0xf;
-		ctx->current_bus = address;
-
-		// If the branch address points to a buffer outside of the current buffer, advance
-		// to the next buffer.
-		if (address < desc->buffer_bus || address >= desc->buffer_bus + desc->used)
-			desc = list_entry(desc->list.next, struct descriptor_buffer, list);
-		d = desc->buffer + (address - desc->buffer_bus) / sizeof(*d);
-		last = find_branch_descriptor(d, z);
-
-		if (!ctx->callback(ctx, d, last))
-			break;
-
-		if (old_desc != desc) {
-			// If we've advanced to the next buffer, move the previous buffer to the
-			// free list.
-			old_desc->used = 0;
-			guard(spinlock_irqsave)(&ctx->ohci->lock);
-			list_move_tail(&old_desc->list, &ctx->buffer_list);
-		}
-		ctx->last = last;
-	}
-}
-
 /*
  * Allocate a new buffer and add it to the list of free buffers for this
  * context.  Must be called with ohci->lock held.
@@ -3169,7 +3128,6 @@ static struct fw_iso_context *ohci_allocate_iso_context(struct fw_card *card,
 	ret = context_init(&ctx->context, ohci, regs, callback);
 	if (ret < 0)
 		goto out_with_header;
-	fw_iso_context_init_work(&ctx->base, ohci_isoc_context_work);
 
 	if (type == FW_ISO_CONTEXT_RECEIVE_MULTICHANNEL) {
 		set_multichannel_mask(ohci, 0);
@@ -3624,7 +3582,8 @@ static int ohci_flush_iso_completions(struct fw_iso_context *base)
 	int ret = 0;
 
 	if (!test_and_set_bit_lock(0, &ctx->flushing_completions)) {
-		ohci_isoc_context_work(&base->work);
+		// Note that tasklet softIRQ is not used to process isochronous context anymore.
+		context_tasklet((unsigned long)&ctx->context);
 
 		switch (base->type) {
 		case FW_ISO_CONTEXT_TRANSMIT: