[PATCH] libata: implement ata_wait_register()

As waiting for some register bits to change seems to be a common
operation shared by some controllers, implement helper function
ata_wait_register().  This function also takes care of register write
flushing.

Note that the condition is inverted, the wait is over when the masked
value does NOT match @val.  As we're waiting for bits to change, this
test is more powerful and allows the function to be used in more
places.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 47 insertions, 0 deletions

diff --git a/drivers/scsi/libata-core.c b/drivers/scsi/libata-core.c
index 2d76ce23728f..0075fe7404d5 100644
--- a/drivers/scsi/libata-core.c
+++ b/drivers/scsi/libata-core.c
@@ -5029,6 +5029,52 @@ int ata_ratelimit(void)
         return rc;
 }
 
+/**
+ *      ata_wait_register - wait until register value changes
+ *      @reg: IO-mapped register
+ *      @mask: Mask to apply to read register value
+ *      @val: Wait condition
+ *      @interval_msec: polling interval in milliseconds
+ *      @timeout_msec: timeout in milliseconds
+ *
+ *      Waiting for some bits of register to change is a common
+ *      operation for ATA controllers.  This function reads 32bit LE
+ *      IO-mapped register @reg and tests for the following condition.
+ *
+ *      (*@reg & mask) != val
+ *
+ *      If the condition is met, it returns; otherwise, the process is
+ *      repeated after @interval_msec until timeout.
+ *
+ *      LOCKING:
+ *      Kernel thread context (may sleep)
+ *
+ *      RETURNS:
+ *      The final register value.
+ */
+u32 ata_wait_register(void __iomem *reg, u32 mask, u32 val,
+                      unsigned long interval_msec,
+                      unsigned long timeout_msec)
+{
+        unsigned long timeout;
+        u32 tmp;
+
+        tmp = ioread32(reg);
+
+        /* Calculate timeout _after_ the first read to make sure
+         * preceding writes reach the controller before starting to
+         * eat away the timeout.
+         */
+        timeout = jiffies + (timeout_msec * HZ) / 1000;
+
+        while ((tmp & mask) == val && time_before(jiffies, timeout)) {
+                msleep(interval_msec);
+                tmp = ioread32(reg);
+        }
+
+        return tmp;
+}
+
 /*
  * libata is essentially a library of internal helper functions for
  * low-level ATA host controller drivers.  As such, the API/ABI is
@@ -5079,6 +5125,7 @@ EXPORT_SYMBOL_GPL(ata_dev_classify);
 EXPORT_SYMBOL_GPL(ata_dev_pair);
 EXPORT_SYMBOL_GPL(ata_port_disable);
 EXPORT_SYMBOL_GPL(ata_ratelimit);
+EXPORT_SYMBOL_GPL(ata_wait_register);
 EXPORT_SYMBOL_GPL(ata_busy_sleep);
 EXPORT_SYMBOL_GPL(ata_port_queue_task);
 EXPORT_SYMBOL_GPL(ata_scsi_ioctl);