From aaff12039ffd812d0c8bbff50b87b6f1f09bec3e Mon Sep 17 00:00:00 2001 From: Stefan Richter Date: Sun, 7 Aug 2011 15:20:18 +0200 Subject: [PATCH] firewire: core: handle ack_busy when fetching the Config ROM MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Some older Panasonic made camcorders (Panasonic AG-EZ30 and NV-DX110, Grundig Scenos DLC 2000) reject requests with ack_busy_X if a request is sent immediately after they sent a response to a prior transaction. This causes firewire-core to fail probing of the camcorder with "giving up on config rom for node id ...". Consequently, programs like kino or dvgrab are unaware of the presence of a camcorder. Such transaction failures happen also with the ieee1394 driver stack (of the 2.4...2.6 kernel series until 2.6.36 inclusive) but with a lower likelihood, such that kino or dvgrab are generally able to use these camcorders via the older driver stack. The cause for firewire-ohci's or firewire-core's worse behavior is not yet known. Gap count optimization in firewire-core is not the cause. Perhaps the slightly higher latency of transaction completion in the older stack plays a role. (ieee1394: AR-resp DMA context tasklet -> packet completion ktread -> user process; firewire-core: tasklet -> user process.) This change introduces retries and delays after ack_busy_X into firewire-core's Config ROM reader, such that at least firewire-core's probing and /dev/fw* creation are successful. This still leaves the problem that userland processes are facing transaction failures. gscanbus's built-in retry routines deal with them successfully, but neither kino's nor dvgrab's do ever succeed. But at least DV capture with "dvgrab -noavc -card 0" works now. Live video preview in kino works too, but not actual capture. One way to prevent Configuration ROM reading failures in application programs is to modify libraw1394 to synthesize read responses by means of firewire-core's Configuration ROM cache. This would only leave CMP and FCP transaction failures as a potential problem source for applications. Reported-and-tested-by: Thomas Seilund Reported-and-tested-by: René Fritz Signed-off-by: Stefan Richter --- drivers/firewire/core-device.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/drivers/firewire/core-device.c b/drivers/firewire/core-device.c index 95a471401892..9f661e069318 100644 --- a/drivers/firewire/core-device.c +++ b/drivers/firewire/core-device.c @@ -455,15 +455,20 @@ static struct device_attribute fw_device_attributes[] = { static int read_rom(struct fw_device *device, int generation, int index, u32 *data) { - int rcode; + u64 offset = (CSR_REGISTER_BASE | CSR_CONFIG_ROM) + index * 4; + int i, rcode; /* device->node_id, accessed below, must not be older than generation */ smp_rmb(); - rcode = fw_run_transaction(device->card, TCODE_READ_QUADLET_REQUEST, - device->node_id, generation, device->max_speed, - (CSR_REGISTER_BASE | CSR_CONFIG_ROM) + index * 4, - data, 4); + for (i = 10; i < 100; i += 10) { + rcode = fw_run_transaction(device->card, + TCODE_READ_QUADLET_REQUEST, device->node_id, + generation, device->max_speed, offset, data, 4); + if (rcode != RCODE_BUSY) + break; + msleep(i); + } be32_to_cpus(data); return rcode; -- 2.39.2