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AXI locked access

Note: This was originally posted on 29th May 2008 at http://forums.arm.com

Does a locked request on either the read or write channel cause both channels to be locked? For example, one master request a locked write transaction to a slave, the read channel also will be locked? if both channels have been locked, whether a read unlock  access also can complete the whole locked sequence?
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  • Note: This was originally posted on 30th May 2008 at http://forums.arm.com

    Hello spark,

    > Does a locked request on either the read or write channel cause both channels to be locked?

    It would have to, otherwise another master could access the "locked" slave on the other data channel, and thus mean the slave is not completely locked.

    The AXI spec states in section 6.3 "...the interconnect must ensure that only that master is allowed access to the slave region...", so it doesn't state read or write access, just any access.

    > For example, one master request a locked write transaction to a slave, the read channel also will be locked?

    Yes, once all pending read or write transfers the slave has accepted have been completed.

    > if both channels have been locked, whether a read unlock  access also can complete the whole locked sequence?

    It would have to as you can't have the slave WRITE locked but READ unlocked.

    JD
Reply
  • Note: This was originally posted on 30th May 2008 at http://forums.arm.com

    Hello spark,

    > Does a locked request on either the read or write channel cause both channels to be locked?

    It would have to, otherwise another master could access the "locked" slave on the other data channel, and thus mean the slave is not completely locked.

    The AXI spec states in section 6.3 "...the interconnect must ensure that only that master is allowed access to the slave region...", so it doesn't state read or write access, just any access.

    > For example, one master request a locked write transaction to a slave, the read channel also will be locked?

    Yes, once all pending read or write transfers the slave has accepted have been completed.

    > if both channels have been locked, whether a read unlock  access also can complete the whole locked sequence?

    It would have to as you can't have the slave WRITE locked but READ unlocked.

    JD
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