firewire: core: integrate software-forced bus resets with bus management

Bus resets which are triggered
  - by the kernel drivers after updates of the local nodes' config ROM,
  - by userspace software via ioctl
shall be deferred until after >=2 seconds after the last bus reset.

If multiple modifications of the local nodes' config ROM happen in a row,
only a single bus reset should happen after them.

When the local node's link goes from inactive to active or vice versa,
and at the two occasions of bus resets mentioned above --- and if the
current gap count differs from 63 --- the bus reset should be preceded
by a PHY configuration packet that reaffirms the gap count.  Otherwise a
bus manager would have to reset the bus again right after that.

This is necessary to promote bus stability, e.g. leave grace periods for
allocations and reallocations of isochronous channels and bandwidth,
SBP-2 reconnections etc.; see IEEE 1394 clause 8.2.1.

This change implements all of the above by moving bus reset initiation
into a delayed work (except for bus resets which are triggered by the
bus manager workqueue job and are performed there immediately).  It
comes with a necessary addition to the card driver methods that allows
to get the current gap count from PHY registers.

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

1 files changed, 38 insertions, 15 deletions

diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c
index a4bbf3dadf58..bb6a92bc9e6a 100644
--- a/drivers/firewire/ohci.c
+++ b/drivers/firewire/ohci.c
@@ -34,6 +34,7 @@
 #include <linux/mm.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
+#include <linux/mutex.h>
 #include <linux/pci.h>
 #include <linux/pci_ids.h>
 #include <linux/spinlock.h>
@@ -182,6 +183,8 @@ struct fw_ohci {
          */
         spinlock_t lock;
 
+        struct mutex phy_reg_mutex;
+
         struct ar_context ar_request_ctx;
         struct ar_context ar_response_ctx;
         struct context at_request_ctx;
@@ -517,13 +520,10 @@ static int write_phy_reg(const struct fw_ohci *ohci, int addr, u32 val)
         return -EBUSY;
 }
 
-static int ohci_update_phy_reg(struct fw_card *card, int addr,
-                               int clear_bits, int set_bits)
+static int update_phy_reg(struct fw_ohci *ohci, int addr,
+                          int clear_bits, int set_bits)
 {
-        struct fw_ohci *ohci = fw_ohci(card);
-        int ret;
-
-        ret = read_phy_reg(ohci, addr);
+        int ret = read_phy_reg(ohci, addr);
         if (ret < 0)
                 return ret;
 
@@ -541,13 +541,38 @@ static int read_paged_phy_reg(struct fw_ohci *ohci, int page, int addr)
 {
         int ret;
 
-        ret = ohci_update_phy_reg(&ohci->card, 7, PHY_PAGE_SELECT, page << 5);
+        ret = update_phy_reg(ohci, 7, PHY_PAGE_SELECT, page << 5);
         if (ret < 0)
                 return ret;
 
         return read_phy_reg(ohci, addr);
 }
 
+static int ohci_read_phy_reg(struct fw_card *card, int addr)
+{
+        struct fw_ohci *ohci = fw_ohci(card);
+        int ret;
+
+        mutex_lock(&ohci->phy_reg_mutex);
+        ret = read_phy_reg(ohci, addr);
+        mutex_unlock(&ohci->phy_reg_mutex);
+
+        return ret;
+}
+
+static int ohci_update_phy_reg(struct fw_card *card, int addr,
+                               int clear_bits, int set_bits)
+{
+        struct fw_ohci *ohci = fw_ohci(card);
+        int ret;
+
+        mutex_lock(&ohci->phy_reg_mutex);
+        ret = update_phy_reg(ohci, addr, clear_bits, set_bits);
+        mutex_unlock(&ohci->phy_reg_mutex);
+
+        return ret;
+}
+
 static int ar_context_add_page(struct ar_context *ctx)
 {
         struct device *dev = ctx->ohci->card.device;
@@ -1676,7 +1701,7 @@ static int configure_1394a_enhancements(struct fw_ohci *ohci)
                 clear = PHY_ENABLE_ACCEL | PHY_ENABLE_MULTI;
                 set = 0;
         }
-        ret = ohci_update_phy_reg(&ohci->card, 5, clear, set);
+        ret = update_phy_reg(ohci, 5, clear, set);
         if (ret < 0)
                 return ret;
 
@@ -1856,12 +1881,8 @@ static int ohci_enable(struct fw_card *card,
                   OHCI1394_HCControl_BIBimageValid);
         flush_writes(ohci);
 
-        /*
-         * We are ready to go, initiate bus reset to finish the
-         * initialization.
-         */
-
-        fw_core_initiate_bus_reset(&ohci->card, 1);
+        /* We are ready to go, reset bus to finish initialization. */
+        fw_schedule_bus_reset(&ohci->card, false, true);
 
         return 0;
 }
@@ -1936,7 +1957,7 @@ static int ohci_set_config_rom(struct fw_card *card,
          * takes effect.
          */
         if (ret == 0)
-                fw_core_initiate_bus_reset(&ohci->card, 1);
+                fw_schedule_bus_reset(&ohci->card, true, true);
         else
                 dma_free_coherent(ohci->card.device, CONFIG_ROM_SIZE,
                                   next_config_rom, next_config_rom_bus);
@@ -2570,6 +2591,7 @@ static int ohci_queue_iso(struct fw_iso_context *base,
 
 static const struct fw_card_driver ohci_driver = {
         .enable                 = ohci_enable,
+        .read_phy_reg           = ohci_read_phy_reg,
         .update_phy_reg         = ohci_update_phy_reg,
         .set_config_rom         = ohci_set_config_rom,
         .send_request           = ohci_send_request,
@@ -2645,6 +2667,7 @@ static int __devinit pci_probe(struct pci_dev *dev,
         pci_set_drvdata(dev, ohci);
 
         spin_lock_init(&ohci->lock);
+        mutex_init(&ohci->phy_reg_mutex);
 
         tasklet_init(&ohci->bus_reset_tasklet,
                      bus_reset_tasklet, (unsigned long)ohci);