firewire: core: fix unstable I/O with Canon camcorder

commit 6044565af458e7fa6e748bff437ecc49dea88d79 upstream.

Regression since commit 10389536742c, "firewire: core: check for 1394a
compliant IRM, fix inaccessibility of Sony camcorder":

The camcorder Canon MV5i generates lots of bus resets when asynchronous
requests are sent to it (e.g. Config ROM read requests or FCP Command
write requests) if the camcorder is not root node.  This causes drop-
outs in videos or makes the camcorder entirely inaccessible.
https://bugzilla.redhat.com/show_bug.cgi?id=633260

Fix this by allowing any Canon device, even if it is a pre-1394a IRM
like MV5i are, to remain root node (if it is at least Cycle Master
capable).  With the FireWire controller cards that I tested, MV5i always
becomes root node when plugged in and left to its own devices.

Reported-by: Ralf Lange
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/firewire/core-card.c b/drivers/firewire/core-card.c
index 991447baba41b90660d0fa6015f152679f4267f6..611fe9207cf5382ffd0aae15068cad6795470c2f 100644 (file)
--- a/drivers/firewire/core-card.c
+++ b/drivers/firewire/core-card.c
@@ -75,6 +75,8 @@ static size_t config_rom_length = 1 + 4 + 1 + 1;
 #define BIB_CMC                        ((1) << 30)
 #define BIB_IMC                        ((1) << 31)
 
+#define CANON_OUI              0x000085
+
 static void generate_config_rom(struct fw_card *card, __be32 *config_rom)
 {
        struct fw_descriptor *desc;
@@ -240,6 +242,7 @@ static void fw_card_bm_work(struct work_struct *work)
        bool root_device_is_running;
        bool root_device_is_cmc;
        bool irm_is_1394_1995_only;
+       bool keep_this_irm;
 
        spin_lock_irqsave(&card->lock, flags);
 
@@ -261,6 +264,10 @@ static void fw_card_bm_work(struct work_struct *work)
        irm_is_1394_1995_only = irm_device && irm_device->config_rom &&
                        (irm_device->config_rom[2] & 0x000000f0) == 0;
 
+       /* Canon MV5i works unreliably if it is not root node. */
+       keep_this_irm = irm_device && irm_device->config_rom &&
+                       irm_device->config_rom[3] >> 8 == CANON_OUI;
+
        root_id  = root_node->node_id;
        irm_id   = card->irm_node->node_id;
        local_id = card->local_node->node_id;
@@ -288,7 +295,7 @@ static void fw_card_bm_work(struct work_struct *work)
                        goto pick_me;
                }
 
-               if (irm_is_1394_1995_only) {
+               if (irm_is_1394_1995_only && !keep_this_irm) {
                        new_root_id = local_id;
                        fw_notify("%s, making local node (%02x) root.\n",
                                  "IRM is not 1394a compliant", new_root_id);
@@ -322,7 +329,7 @@ static void fw_card_bm_work(struct work_struct *work)
 
                spin_lock_irqsave(&card->lock, flags);
 
-               if (rcode != RCODE_COMPLETE) {
+               if (rcode != RCODE_COMPLETE && !keep_this_irm) {
                        /*
                         * The lock request failed, maybe the IRM
                         * isn't really IRM capable after all. Let's