firewire: core: optimize propagation of BROADCAST_CHANNEL

Cache the test result of whether a device implements BROADCAST_CHANNEL.
This minimizes traffic on the bus after each bus reset.  A majority of
devices does not implement BROADCAST_CHANNEL.

Remove busy retries; just rely on the hardware to retry requests to busy
responders.  Remove unnecessary log messages.

Rename the flag is_irm to broadcast_channel_allocated to better reflect
its meaning.  Reset the flag earlier in fw_core_handle_bus_reset.

Pass the generation down as a call parameter; that way generation can't
be newer than card->broadcast_channel_allocated and device->node_id.

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

5 files changed, 52 insertions, 90 deletions

diff --git a/drivers/firewire/fw-card.c b/drivers/firewire/fw-card.c
index d63d0ed9e048..8b8c8c22f0fc 100644
--- a/drivers/firewire/fw-card.c
+++ b/drivers/firewire/fw-card.c
@@ -181,83 +181,9 @@ void fw_core_remove_descriptor(struct fw_descriptor *desc)
         mutex_unlock(&card_mutex);
 }
 
-#define IRM_RETRIES 2
-
-/*
- * The abi is set by device_for_each_child(), even though we have no use
- * for data, nor do we have a meaningful return value.
- */
-int fw_irm_set_broadcast_channel_register(struct device *dev, void *data)
+static int set_broadcast_channel(struct device *dev, void *data)
 {
-        struct fw_device *d;
-        int rcode;
-        int node_id;
-        int max_speed;
-        int retries;
-        int generation;
-        __be32 regval;
-        struct fw_card *card;
-
-        d = fw_device(dev);
-        /* FIXME: do we need locking here? */
-        generation = d->generation;
-        smp_rmb(); /* Ensure generation is at least as old as node_id */
-        node_id = d->node_id;
-        max_speed = d->max_speed;
-        retries = IRM_RETRIES;
-        card = d->card;
-tryagain_r:
-        rcode = fw_run_transaction(card, TCODE_READ_QUADLET_REQUEST,
-                                   node_id, generation, max_speed,
-                                   CSR_REGISTER_BASE + CSR_BROADCAST_CHANNEL,
-                                   &regval, 4);
-        switch (rcode) {
-        case RCODE_BUSY:
-                if (retries--)
-                        goto tryagain_r;
-                fw_notify("node %x read broadcast channel busy\n",
-                          node_id);
-                return 0;
-
-        default:
-                fw_notify("node %x read broadcast channel failed %x\n",
-                          node_id, rcode);
-                return 0;
-
-        case RCODE_COMPLETE:
-                /*
-                 * Paranoid reporting of nonstandard broadcast channel
-                 * contents goes here
-                 */
-                if (regval != cpu_to_be32(BROADCAST_CHANNEL_INITIAL))
-                        return 0;
-                break;
-        }
-        retries = IRM_RETRIES;
-        regval = cpu_to_be32(BROADCAST_CHANNEL_INITIAL |
-                             BROADCAST_CHANNEL_VALID);
-tryagain_w:
-        rcode = fw_run_transaction(card,
-                        TCODE_WRITE_QUADLET_REQUEST, node_id,
-                        generation, max_speed,
-                        CSR_REGISTER_BASE + CSR_BROADCAST_CHANNEL,
-                        &regval, 4);
-        switch (rcode) {
-        case RCODE_BUSY:
-                if (retries--)
-                        goto tryagain_w;
-                fw_notify("node %x write broadcast channel busy\n",
-                          node_id);
-                return 0;
-
-        default:
-                fw_notify("node %x write broadcast channel failed %x\n",
-                          node_id, rcode);
-                return 0;
-
-        case RCODE_COMPLETE:
-                return 0;
-        }
+        fw_device_set_broadcast_channel(fw_device(dev), (long)data);
         return 0;
 }
 
@@ -268,9 +194,9 @@ static void allocate_broadcast_channel(struct fw_card *card, int generation)
         fw_iso_resource_manage(card, generation, 1ULL << 31,
                                &channel, &bandwidth, true);
         if (channel == 31) {
-                card->is_irm = true;
-                device_for_each_child(card->device, NULL,
-                                      fw_irm_set_broadcast_channel_register);
+                card->broadcast_channel_allocated = true;
+                device_for_each_child(card->device, (void *)(long)generation,
+                                      set_broadcast_channel);
         }
 }
 
@@ -302,7 +228,6 @@ static void fw_card_bm_work(struct work_struct *work)
         __be32 lock_data[2];
 
         spin_lock_irqsave(&card->lock, flags);
-        card->is_irm = false;
 
         if (card->local_node == NULL) {
                 spin_unlock_irqrestore(&card->lock, flags);
diff --git a/drivers/firewire/fw-device.c b/drivers/firewire/fw-device.c
index a40444e8eb20..a47e2129d83d 100644
--- a/drivers/firewire/fw-device.c
+++ b/drivers/firewire/fw-device.c
@@ -518,7 +518,7 @@ static int read_bus_info_block(struct fw_device *device, int generation)
 
         kfree(old_rom);
         ret = 0;
-        device->cmc = rom[2] & 1 << 30;
+        device->cmc = rom[2] >> 30 & 1;
  out:
         kfree(rom);
 
@@ -756,6 +756,44 @@ static int lookup_existing_device(struct device *dev, void *data)
         return match;
 }
 
+enum { BC_UNKNOWN = 0, BC_UNIMPLEMENTED, BC_IMPLEMENTED, };
+
+void fw_device_set_broadcast_channel(struct fw_device *device, int generation)
+{
+        struct fw_card *card = device->card;
+        __be32 data;
+        int rcode;
+
+        if (!card->broadcast_channel_allocated)
+                return;
+
+        if (device->bc_implemented == BC_UNKNOWN) {
+                rcode = fw_run_transaction(card, TCODE_READ_QUADLET_REQUEST,
+                                device->node_id, generation, device->max_speed,
+                                CSR_REGISTER_BASE + CSR_BROADCAST_CHANNEL,
+                                &data, 4);
+                switch (rcode) {
+                case RCODE_COMPLETE:
+                        if (data & cpu_to_be32(1 << 31)) {
+                                device->bc_implemented = BC_IMPLEMENTED;
+                                break;
+                        }
+                        /* else fall through to case address error */
+                case RCODE_ADDRESS_ERROR:
+                        device->bc_implemented = BC_UNIMPLEMENTED;
+                }
+        }
+
+        if (device->bc_implemented == BC_IMPLEMENTED) {
+                data = cpu_to_be32(BROADCAST_CHANNEL_INITIAL |
+                                   BROADCAST_CHANNEL_VALID);
+                fw_run_transaction(card, TCODE_WRITE_QUADLET_REQUEST,
+                                device->node_id, generation, device->max_speed,
+                                CSR_REGISTER_BASE + CSR_BROADCAST_CHANNEL,
+                                &data, 4);
+        }
+}
+
 static void fw_device_init(struct work_struct *work)
 {
         struct fw_device *device =
@@ -849,9 +887,8 @@ static void fw_device_init(struct work_struct *work)
                                   device->config_rom[3], device->config_rom[4],
                                   1 << device->max_speed);
                 device->config_rom_retries = 0;
-                if (device->card->is_irm)
-                        fw_irm_set_broadcast_channel_register(&device->device,
-                                                              NULL);
+
+                fw_device_set_broadcast_channel(device, device->generation);
         }
 
         /*
diff --git a/drivers/firewire/fw-device.h b/drivers/firewire/fw-device.h
index 3085a74669b5..97588937c018 100644
--- a/drivers/firewire/fw-device.h
+++ b/drivers/firewire/fw-device.h
@@ -71,7 +71,6 @@ struct fw_device {
         int node_id;
         int generation;
         unsigned max_speed;
-        bool cmc;
         struct fw_card *card;
         struct device device;
 
@@ -81,6 +80,9 @@ struct fw_device {
         u32 *config_rom;
         size_t config_rom_length;
         int config_rom_retries;
+        unsigned cmc:1;
+        unsigned bc_implemented:2;
+
         struct delayed_work work;
         struct fw_attribute_group attribute_group;
 };
@@ -109,6 +111,7 @@ static inline void fw_device_put(struct fw_device *device)
 
 struct fw_device *fw_device_get_by_devt(dev_t devt);
 int fw_device_enable_phys_dma(struct fw_device *device);
+void fw_device_set_broadcast_channel(struct fw_device *device, int generation);
 
 void fw_device_cdev_update(struct fw_device *device);
 void fw_device_cdev_remove(struct fw_device *device);
diff --git a/drivers/firewire/fw-topology.c b/drivers/firewire/fw-topology.c
index b44131cf0c62..d0deecc4de93 100644
--- a/drivers/firewire/fw-topology.c
+++ b/drivers/firewire/fw-topology.c
@@ -526,6 +526,7 @@ void fw_core_handle_bus_reset(struct fw_card *card, int node_id, int generation,
 
         spin_lock_irqsave(&card->lock, flags);
 
+        card->broadcast_channel_allocated = false;
         card->node_id = node_id;
         /*
          * Update node_id before generation to prevent anybody from using
diff --git a/drivers/firewire/fw-transaction.h b/drivers/firewire/fw-transaction.h
index d4f42cecbdfa..dfa799068f89 100644
--- a/drivers/firewire/fw-transaction.h
+++ b/drivers/firewire/fw-transaction.h
@@ -230,11 +230,6 @@ struct fw_card {
         u8 color; /* must be u8 to match the definition in struct fw_node */
         int gap_count;
         bool beta_repeaters_present;
-        /*
-         * Set if the local device is the IRM and the broadcast channel
-         * was allocated.
-         */
-        bool is_irm;
 
         int index;
 
@@ -245,6 +240,7 @@ struct fw_card {
         int bm_retries;
         int bm_generation;
 
+        bool broadcast_channel_allocated;
         u32 broadcast_channel;
         u32 topology_map[(CSR_TOPOLOGY_MAP_END - CSR_TOPOLOGY_MAP) / 4];
 };