firewire: core: use union for callback of transaction completion

In 1394 OHCI, the OUTPUT_LAST descriptor of Asynchronous Transmit (AT)
request context has timeStamp field, in which 1394 OHCI controller
record the isochronous cycle when the packet was sent for the request
subaction. Additionally, for the case of split transaction in IEEE 1394,
Asynchronous Receive (AT) request context is used for response subaction
to finish the transaction. The trailer quadlet of descriptor in the
context has timeStamp field, in which 1394 OHCI controller records the
isochronous cycle when the packet arrived.

Current implementation of 1394 OHCI controller driver stores values of
both fields to internal structure as time stamp, while Linux FireWire
subsystem provides no way to access to it. When using asynchronous
transaction service provided by the subsystem, callback function is passed
to kernel API. The prototype of callback function has the lack of argument
for the values.

This commit adds a new callback function for the purpose. It has an
additional argument to point to the constant array with two elements. For
backward compatibility to kernel space, a new union is also adds to wrap
two different prototype of callback function. The fw_transaction structure
has the union as a member and a boolean flag to express which function
callback is available.

The core function is changed to handle the two cases; with or without
time stamp. For the error path to process transaction, the isochronous
cycle is computed by current value of CYCLE_TIMER register in 1394 OHCI
controller. Especially for the case of timeout of split transaction, the
expected isochronous cycle is computed.

Link: https://lore.kernel.org/r/20230529113406.986289-6-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>

1 files changed, 15 insertions, 2 deletions

diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c
index 17c9d825188b..06386c3b7f03 100644
--- a/drivers/firewire/ohci.c
+++ b/drivers/firewire/ohci.c
@@ -1623,6 +1623,8 @@ static void handle_local_request(struct context *ctx, struct fw_packet *packet)
 	}
 }
 
+static u32 get_cycle_time(struct fw_ohci *ohci);
+
 static void at_context_transmit(struct context *ctx, struct fw_packet *packet)
 {
 	unsigned long flags;
@@ -1633,6 +1635,10 @@ static void at_context_transmit(struct context *ctx, struct fw_packet *packet)
 	if (HEADER_GET_DESTINATION(packet->header[0]) == ctx->ohci->node_id &&
 	    ctx->ohci->generation == packet->generation) {
 		spin_unlock_irqrestore(&ctx->ohci->lock, flags);
+
+		// Timestamping on behalf of the hardware.
+		packet->timestamp = cycle_time_to_ohci_tstamp(get_cycle_time(ctx->ohci));
+
 		handle_local_request(ctx, packet);
 		return;
 	}
@@ -1640,9 +1646,12 @@ static void at_context_transmit(struct context *ctx, struct fw_packet *packet)
 	ret = at_context_queue_packet(ctx, packet);
 	spin_unlock_irqrestore(&ctx->ohci->lock, flags);
 
-	if (ret < 0)
-		packet->callback(packet, &ctx->ohci->card, packet->ack);
+	if (ret < 0) {
+		// Timestamping on behalf of the hardware.
+		packet->timestamp = cycle_time_to_ohci_tstamp(get_cycle_time(ctx->ohci));
 
+		packet->callback(packet, &ctx->ohci->card, packet->ack);
+	}
 }
 
 static void detect_dead_context(struct fw_ohci *ohci,
@@ -2557,6 +2566,10 @@ static int ohci_cancel_packet(struct fw_card *card, struct fw_packet *packet)
 	log_ar_at_event(ohci, 'T', packet->speed, packet->header, 0x20);
 	driver_data->packet = NULL;
 	packet->ack = RCODE_CANCELLED;
+
+	// Timestamping on behalf of the hardware.
+	packet->timestamp = cycle_time_to_ohci_tstamp(get_cycle_time(ohci));
+
 	packet->callback(packet, &ohci->card, packet->ack);
 	ret = 0;
  out: