firewire: allow explicit flushing of iso packet completions

Extend the kernel and userspace APIs to allow reporting all currently
completed isochronous packets, even if the next interrupt packet has not
yet been reached.  This is required to determine the status of the
packets at the end of a paused or stopped stream, and useful for more
precise synchronization of audio streams.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

drivers/firewire/core-card.c

@@ -650,6 +650,11 @@ static void dummy_flush_queue_iso(struct fw_iso_context *ctx)
 {
 }
 
+static int dummy_flush_iso_completions(struct fw_iso_context *ctx)
+{
+	return -ENODEV;
+}
+
 static const struct fw_card_driver dummy_driver_template = {
 	.read_phy_reg		= dummy_read_phy_reg,
 	.update_phy_reg		= dummy_update_phy_reg,
@@ -662,6 +667,7 @@ static const struct fw_card_driver dummy_driver_template = {
 	.set_iso_channels	= dummy_set_iso_channels,
 	.queue_iso		= dummy_queue_iso,
 	.flush_queue_iso	= dummy_flush_queue_iso,
+	.flush_iso_completions	= dummy_flush_iso_completions,
 };
 
 void fw_card_release(struct kref *kref)

drivers/firewire/core-cdev.c

@@ -438,6 +438,7 @@ union ioctl_arg {
 	struct fw_cdev_send_phy_packet		send_phy_packet;
 	struct fw_cdev_receive_phy_packets	receive_phy_packets;
 	struct fw_cdev_set_iso_channels		set_iso_channels;
+	struct fw_cdev_flush_iso		flush_iso;
 };
 
 static int ioctl_get_info(struct client *client, union ioctl_arg *arg)
@@ -1168,6 +1169,16 @@ static int ioctl_stop_iso(struct client *client, union ioctl_arg *arg)
 	return fw_iso_context_stop(client->iso_context);
 }
 
+static int ioctl_flush_iso(struct client *client, union ioctl_arg *arg)
+{
+	struct fw_cdev_flush_iso *a = &arg->flush_iso;
+
+	if (client->iso_context == NULL || a->handle != 0)
+		return -EINVAL;
+
+	return fw_iso_context_flush_completions(client->iso_context);
+}
+
 static int ioctl_get_cycle_timer2(struct client *client, union ioctl_arg *arg)
 {
 	struct fw_cdev_get_cycle_timer2 *a = &arg->get_cycle_timer2;
@@ -1589,6 +1600,7 @@ static int (* const ioctl_handlers[])(struct client *, union ioctl_arg *) = {
 	[0x15] = ioctl_send_phy_packet,
 	[0x16] = ioctl_receive_phy_packets,
 	[0x17] = ioctl_set_iso_channels,
+	[0x18] = ioctl_flush_iso,
 };
 
 static int dispatch_ioctl(struct client *client,

drivers/firewire/core-iso.c

@@ -191,6 +191,12 @@ void fw_iso_context_queue_flush(struct fw_iso_context *ctx)
 }
 EXPORT_SYMBOL(fw_iso_context_queue_flush);
 
+int fw_iso_context_flush_completions(struct fw_iso_context *ctx)
+{
+	return ctx->card->driver->flush_iso_completions(ctx);
+}
+EXPORT_SYMBOL(fw_iso_context_flush_completions);
+
 int fw_iso_context_stop(struct fw_iso_context *ctx)
 {
 	return ctx->card->driver->stop_iso(ctx);

drivers/firewire/core.h

@@ -106,6 +106,8 @@ struct fw_card_driver {
 
 	void (*flush_queue_iso)(struct fw_iso_context *ctx);
 
+	int (*flush_iso_completions)(struct fw_iso_context *ctx);
+
 	int (*stop_iso)(struct fw_iso_context *ctx);
 };
 

drivers/firewire/ohci.c

@@ -172,6 +172,9 @@ struct iso_context {
 	struct context context;
 	void *header;
 	size_t header_length;
+	unsigned long flushing_completions;
+	u32 mc_buffer_bus;
+	u16 mc_completed;
 	u16 last_timestamp;
 	u8 sync;
 	u8 tags;
@@ -2749,28 +2752,51 @@ static int handle_ir_buffer_fill(struct context *context,
 {
 	struct iso_context *ctx =
 		container_of(context, struct iso_context, context);
+	unsigned int req_count, res_count, completed;
 	u32 buffer_dma;
 
-	if (last->res_count != 0)
+	req_count = le16_to_cpu(last->req_count);
+	res_count = le16_to_cpu(ACCESS_ONCE(last->res_count));
+	completed = req_count - res_count;
+	buffer_dma = le32_to_cpu(last->data_address);
+
+	if (completed > 0) {
+		ctx->mc_buffer_bus = buffer_dma;
+		ctx->mc_completed = completed;
+	}
+
+	if (res_count != 0)
 		/* Descriptor(s) not done yet, stop iteration */
 		return 0;
 
-	buffer_dma = le32_to_cpu(last->data_address);
 	dma_sync_single_range_for_cpu(context->ohci->card.device,
 				      buffer_dma & PAGE_MASK,
 				      buffer_dma & ~PAGE_MASK,
-				      le16_to_cpu(last->req_count),
-				      DMA_FROM_DEVICE);
+				      completed, DMA_FROM_DEVICE);
 
-	if (last->control & cpu_to_le16(DESCRIPTOR_IRQ_ALWAYS))
+	if (last->control & cpu_to_le16(DESCRIPTOR_IRQ_ALWAYS)) {
 		ctx->base.callback.mc(&ctx->base,
-				      le32_to_cpu(last->data_address) +
-				      le16_to_cpu(last->req_count),
+				      buffer_dma + completed,
 				      ctx->base.callback_data);
+		ctx->mc_completed = 0;
+	}
 
 	return 1;
 }
 
+static void flush_ir_buffer_fill(struct iso_context *ctx)
+{
+	dma_sync_single_range_for_cpu(ctx->context.ohci->card.device,
+				      ctx->mc_buffer_bus & PAGE_MASK,
+				      ctx->mc_buffer_bus & ~PAGE_MASK,
+				      ctx->mc_completed, DMA_FROM_DEVICE);
+
+	ctx->base.callback.mc(&ctx->base,
+			      ctx->mc_buffer_bus + ctx->mc_completed,
+			      ctx->base.callback_data);
+	ctx->mc_completed = 0;
+}
+
 static inline void sync_it_packet_for_cpu(struct context *context,
 					  struct descriptor *pd)
 {
@@ -2925,8 +2951,10 @@ static struct fw_iso_context *ohci_allocate_iso_context(struct fw_card *card,
 	if (ret < 0)
 		goto out_with_header;
 
-	if (type == FW_ISO_CONTEXT_RECEIVE_MULTICHANNEL)
+	if (type == FW_ISO_CONTEXT_RECEIVE_MULTICHANNEL) {
 		set_multichannel_mask(ohci, 0);
+		ctx->mc_completed = 0;
+	}
 
 	return &ctx->base;
 
@@ -3388,6 +3416,39 @@ static void ohci_flush_queue_iso(struct fw_iso_context *base)
 	reg_write(ctx->ohci, CONTROL_SET(ctx->regs), CONTEXT_WAKE);
 }
 
+static int ohci_flush_iso_completions(struct fw_iso_context *base)
+{
+	struct iso_context *ctx = container_of(base, struct iso_context, base);
+	int ret = 0;
+
+	tasklet_disable(&ctx->context.tasklet);
+
+	if (!test_and_set_bit_lock(0, &ctx->flushing_completions)) {
+		context_tasklet((unsigned long)&ctx->context);
+
+		switch (base->type) {
+		case FW_ISO_CONTEXT_TRANSMIT:
+		case FW_ISO_CONTEXT_RECEIVE:
+			if (ctx->header_length != 0)
+				flush_iso_completions(ctx);
+			break;
+		case FW_ISO_CONTEXT_RECEIVE_MULTICHANNEL:
+			if (ctx->mc_completed != 0)
+				flush_ir_buffer_fill(ctx);
+			break;
+		default:
+			ret = -ENOSYS;
+		}
+
+		clear_bit_unlock(0, &ctx->flushing_completions);
+		smp_mb__after_clear_bit();
+	}
+
+	tasklet_enable(&ctx->context.tasklet);
+
+	return ret;
+}
+
 static const struct fw_card_driver ohci_driver = {
 	.enable			= ohci_enable,
 	.read_phy_reg		= ohci_read_phy_reg,
@@ -3405,6 +3466,7 @@ static const struct fw_card_driver ohci_driver = {
 	.set_iso_channels	= ohci_set_iso_channels,
 	.queue_iso		= ohci_queue_iso,
 	.flush_queue_iso	= ohci_flush_queue_iso,
+	.flush_iso_completions	= ohci_flush_iso_completions,
 	.start_iso		= ohci_start_iso,
 	.stop_iso		= ohci_stop_iso,
 };