firewire: allocate broadcast channel in hardware

On OHCI 1.1 controllers, let the hardware allocate the broadcast channel
automatically.  This removes a theoretical race condition directly after
a bus reset where it could be possible to read the channel allocation
register with channel 31 still being unallocated.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>

4 files changed, 26 insertions, 12 deletions

diff --git a/drivers/firewire/core-card.c b/drivers/firewire/core-card.c
index 7c4cf6cfa74..faf2eee473b 100644
--- a/drivers/firewire/core-card.c
+++ b/drivers/firewire/core-card.c
@@ -208,13 +208,19 @@ static void allocate_broadcast_channel(struct fw_card *card, int generation)
 {
         int channel, bandwidth = 0;
 
-        fw_iso_resource_manage(card, generation, 1ULL << 31, &channel,
-                               &bandwidth, true, card->bm_transaction_data);
-        if (channel == 31) {
+        if (!card->broadcast_channel_allocated) {
+                fw_iso_resource_manage(card, generation, 1ULL << 31,
+                                       &channel, &bandwidth, true,
+                                       card->bm_transaction_data);
+                if (channel != 31) {
+                        fw_notify("failed to allocate broadcast channel\n");
+                        return;
+                }
                 card->broadcast_channel_allocated = true;
-                device_for_each_child(card->device, (void *)(long)generation,
-                                      fw_device_set_broadcast_channel);
         }
+
+        device_for_each_child(card->device, (void *)(long)generation,
+                              fw_device_set_broadcast_channel);
 }
 
 static const char gap_count_table[] = {
diff --git a/drivers/firewire/core-topology.c b/drivers/firewire/core-topology.c
index ca3c6531816..00a556f3a58 100644
--- a/drivers/firewire/core-topology.c
+++ b/drivers/firewire/core-topology.c
@@ -543,7 +543,8 @@ 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->broadcast_channel_allocated = (card->driver->get_features(card) &
+                                             FEATURE_CHANNEL_31_ALLOCATED) != 0;
         card->node_id = node_id;
         /*
          * Update node_id before generation to prevent anybody from using
diff --git a/drivers/firewire/core.h b/drivers/firewire/core.h
index a9ace1f8dc3..3f9e39b60bc 100644
--- a/drivers/firewire/core.h
+++ b/drivers/firewire/core.h
@@ -39,6 +39,7 @@ struct fw_packet;
 #define BROADCAST_CHANNEL_VALID         (1 << 30)
 
 #define FEATURE_PRIORITY_BUDGET         0x01
+#define FEATURE_CHANNEL_31_ALLOCATED    0x02
 
 #define CSR_STATE_BIT_CMSTR     (1 << 8)
 #define CSR_STATE_BIT_ABDICATE  (1 << 10)
diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c
index 1dcc2e427eb..51a55808d88 100644
--- a/drivers/firewire/ohci.c
+++ b/drivers/firewire/ohci.c
@@ -171,6 +171,7 @@ struct fw_ohci {
         int request_generation; /* for timestamping incoming requests */
         unsigned quirks;
         unsigned int pri_req_max;
+        unsigned int features;
         u32 bus_time;
         bool is_root;
 
@@ -1694,7 +1695,7 @@ static int ohci_enable(struct fw_card *card,
 {
         struct fw_ohci *ohci = fw_ohci(card);
         struct pci_dev *dev = to_pci_dev(card->device);
-        u32 lps, seconds, irqs;
+        u32 lps, seconds, version, irqs;
         int i, ret;
 
         if (software_reset(ohci)) {
@@ -1747,10 +1748,19 @@ static int ohci_enable(struct fw_card *card,
         reg_write(ohci, OHCI1394_IsochronousCycleTimer, seconds << 25);
         ohci->bus_time = seconds & ~0x3f;
 
+        version = reg_read(ohci, OHCI1394_Version) & 0x00ff00ff;
+        if (version >= OHCI_VERSION_1_1) {
+                reg_write(ohci, OHCI1394_InitialChannelsAvailableHi,
+                          0xfffffffe);
+                ohci->features |= FEATURE_CHANNEL_31_ALLOCATED;
+        }
+
         /* Get implemented bits of the priority arbitration request counter. */
         reg_write(ohci, OHCI1394_FairnessControl, 0x3f);
         ohci->pri_req_max = reg_read(ohci, OHCI1394_FairnessControl) & 0x3f;
         reg_write(ohci, OHCI1394_FairnessControl, 0);
+        if (ohci->pri_req_max != 0)
+                ohci->features |= FEATURE_PRIORITY_BUDGET;
 
         ar_context_run(&ohci->ar_request_ctx);
         ar_context_run(&ohci->ar_response_ctx);
@@ -2124,12 +2134,8 @@ static void ohci_write_csr_reg(struct fw_card *card, int csr_offset, u32 value)
 static unsigned int ohci_get_features(struct fw_card *card)
 {
         struct fw_ohci *ohci = fw_ohci(card);
-        unsigned int features = 0;
-
-        if (ohci->pri_req_max != 0)
-                features |= FEATURE_PRIORITY_BUDGET;
 
-        return features;
+        return ohci->features;
 }
 
 static void copy_iso_headers(struct iso_context *ctx, void *p)