firewire: add CSR PRIORITY_BUDGET support

If supported by the OHCI controller, implement the PRIORITY_BUDGET
register, which is required for nodes that can use asynchronous
priority arbitration.

To allow the core to determine what features the lowlevel device
supports, add a new card driver callback.

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

3 files changed, 45 insertions, 0 deletions

diff --git a/drivers/firewire/core-transaction.c b/drivers/firewire/core-transaction.c
index 8146133818dc..a61eb3fb9573 100644
--- a/drivers/firewire/core-transaction.c
+++ b/drivers/firewire/core-transaction.c
@@ -1126,6 +1126,20 @@ static void handle_registers(struct fw_card *card, struct fw_request *request,
                         rcode = RCODE_TYPE_ERROR;
                 break;
 
+        case CSR_PRIORITY_BUDGET:
+                if (!(card->driver->get_features(card) &
+                                                FEATURE_PRIORITY_BUDGET))
+                        rcode = RCODE_ADDRESS_ERROR;
+                else if (tcode == TCODE_READ_QUADLET_REQUEST)
+                        *data = cpu_to_be32(card->driver->
+                                read_csr_reg(card, CSR_PRIORITY_BUDGET));
+                else if (tcode == TCODE_WRITE_QUADLET_REQUEST)
+                        card->driver->write_csr_reg(card, CSR_PRIORITY_BUDGET,
+                                                    be32_to_cpu(*data));
+                else
+                        rcode = RCODE_TYPE_ERROR;
+                break;
+
         case CSR_BROADCAST_CHANNEL:
                 if (tcode == TCODE_READ_QUADLET_REQUEST)
                         *data = cpu_to_be32(card->broadcast_channel);
diff --git a/drivers/firewire/core.h b/drivers/firewire/core.h
index efcdeb2e31e6..3b8c0f042f49 100644
--- a/drivers/firewire/core.h
+++ b/drivers/firewire/core.h
@@ -38,6 +38,8 @@ struct fw_packet;
 #define BROADCAST_CHANNEL_INITIAL       (1 << 31 | 31)
 #define BROADCAST_CHANNEL_VALID         (1 << 30)
 
+#define FEATURE_PRIORITY_BUDGET         0x01
+
 struct fw_card_driver {
         /*
          * Enable the given card with the given initial config rom.
@@ -78,6 +80,8 @@ struct fw_card_driver {
         u32 (*read_csr_reg)(struct fw_card *card, int csr_offset);
         void (*write_csr_reg)(struct fw_card *card, int csr_offset, u32 value);
 
+        unsigned int (*get_features)(struct fw_card *card);
+
         struct fw_iso_context *
         (*allocate_iso_context)(struct fw_card *card,
                                 int type, int channel, size_t header_size);
diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c
index 9c588fd01250..0e5413531785 100644
--- a/drivers/firewire/ohci.c
+++ b/drivers/firewire/ohci.c
@@ -170,6 +170,7 @@ struct fw_ohci {
         int generation;
         int request_generation; /* for timestamping incoming requests */
         unsigned quirks;
+        unsigned int pri_req_max;
         u32 bus_time;
 
         /*
@@ -1738,6 +1739,11 @@ static int ohci_enable(struct fw_card *card,
         reg_write(ohci, OHCI1394_IsochronousCycleTimer, seconds << 25);
         ohci->bus_time = seconds & ~0x3f;
 
+        /* 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);
+
         ar_context_run(&ohci->ar_request_ctx);
         ar_context_run(&ohci->ar_response_ctx);
 
@@ -2028,6 +2034,10 @@ static u32 ohci_read_csr_reg(struct fw_card *card, int csr_offset)
                 value = reg_read(ohci, OHCI1394_ATRetries);
                 return (value >> 4) & 0x0ffff00f;
 
+        case CSR_PRIORITY_BUDGET:
+                return (reg_read(ohci, OHCI1394_FairnessControl) & 0x3f) |
+                        (ohci->pri_req_max << 8);
+
         default:
                 WARN_ON(1);
                 return 0;
@@ -2065,12 +2075,28 @@ static void ohci_write_csr_reg(struct fw_card *card, int csr_offset, u32 value)
                 flush_writes(ohci);
                 break;
 
+        case CSR_PRIORITY_BUDGET:
+                reg_write(ohci, OHCI1394_FairnessControl, value & 0x3f);
+                flush_writes(ohci);
+                break;
+
         default:
                 WARN_ON(1);
                 break;
         }
 }
 
+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;
+}
+
 static void copy_iso_headers(struct iso_context *ctx, void *p)
 {
         int i = ctx->header_length;
@@ -2510,6 +2536,7 @@ static const struct fw_card_driver ohci_driver = {
         .enable_phys_dma        = ohci_enable_phys_dma,
         .read_csr_reg           = ohci_read_csr_reg,
         .write_csr_reg          = ohci_write_csr_reg,
+        .get_features           = ohci_get_features,
 
         .allocate_iso_context   = ohci_allocate_iso_context,
         .free_iso_context       = ohci_free_iso_context,