Greg Kroah-Hartman
598cf27219
Link: https://lore.kernel.org/r/20260217200002.683975158@linuxfoundation.org Tested-by: Florian Fainelli <florian.fainelli@broadcom.com> Tested-by: Takeshi Ogasawara <takeshi.ogasawara@futuring-girl.com> Tested-by: Peter Schneider <pschneider1968@googlemail.com> Tested-by: Jon Hunter <jonathanh@nvidia.com> Tested-by: Salvatore Bonaccorso <carnil@debian.org> Tested-by: Brett A C Sheffield <bacs@librecast.net> Tested-by: Mark Brown <broonie@kernel.org> Tested-by: Luna Jernberg <droidbittin@gmail.com> Tested-by: Ronald Warsow <rwarsow@gmx.de> Tested-by: Justin M. Forbes <jforbes@fedoraproject.org> Tested-by: Ron Economos <re@w6rz.net> Tested-by: Miguel Ojeda <ojeda@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
52 lines
2.2 KiB
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52 lines
2.2 KiB
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===========================================
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Atomic Operation Control (ATOMCTL) Register
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===========================================
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We Have Atomic Operation Control (ATOMCTL) Register.
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This register determines the effect of using a S32C1I instruction
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with various combinations of:
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1. With and without an Coherent Cache Controller which
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can do Atomic Transactions to the memory internally.
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2. With and without An Intelligent Memory Controller which
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can do Atomic Transactions itself.
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The Core comes up with a default value of for the three types of cache ops::
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0x28: (WB: Internal, WT: Internal, BY:Exception)
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On the FPGA Cards we typically simulate an Intelligent Memory controller
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which can implement RCW transactions. For FPGA cards with an External
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Memory controller we let it to the atomic operations internally while
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doing a Cached (WB) transaction and use the Memory RCW for un-cached
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operations.
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For systems without an coherent cache controller, non-MX, we always
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use the memory controllers RCW, though non-MX controllers likely
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support the Internal Operation.
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CUSTOMER-WARNING:
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Virtually all customers buy their memory controllers from vendors that
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don't support atomic RCW memory transactions and will likely want to
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configure this register to not use RCW.
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Developers might find using RCW in Bypass mode convenient when testing
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with the cache being bypassed; for example studying cache alias problems.
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See Section 4.3.12.4 of ISA; Bits::
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WB WT BY
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5 4 | 3 2 | 1 0
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========= ================== ================== ===============
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2 Bit
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Field
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Values WB - Write Back WT - Write Thru BY - Bypass
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========= ================== ================== ===============
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0 Exception Exception Exception
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1 RCW Transaction RCW Transaction RCW Transaction
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2 Internal Operation Internal Operation Reserved
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3 Reserved Reserved Reserved
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========= ================== ================== ===============
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