Digi NS9215 - Manual (Page 101)

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W O R K I N G W I T H T H E C P U
R10:TLB Lockdown register
www.digiembedded.com 101
8
Write <CRm>==0 to Cache Lockdown register (R9), setting L==1 for bit i and
restoring all other bits to the values they had before the lockdown routine was
started.
Cache unlock
procedure
To unlock the locked down portion of the cache, write to Cache Lockdown register
(R9) setting
L==0 for the appropriate bit. The following sequence, for example, sets
the L bit to 0 for way 0 of the ICache, unlocking way 0:
MRC p15, 0, Rn, c9, c0, 1;
BIC Rn, Rn, 0x01;
MCR p15, 0, Rn, c9, c0, 1;
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R 1 0 : T L B L o c k d o w n r e g i s t e r
The TLB Lockdown register controls where hardware page table walks place the TLB
entry — in the set associative region or the lockdown region of the TLB. If the TLB
entry is put in the lockdown region, the register indicates which entry is written.
The TLB lockdown region contains eight entries (see the discussion of the TLB
structure in "TLB structure," beginning on page 126, for more information).
Register format
P bit
When writing the TLB Lockdown register, the value in the P bit (D0) determines in
which region the TLB entry is placed:
Invalidate
operation
TLB entries in the lockdown region are preserved so invalidate-TLB operations only
invalidate the unpreserved entries in the TLB; that is, those entries in the set-
associative region. Invalidate-TLB single entry operations invalidate any TLB entry
corresponding to the modified virtual address given in
Rd , regardless of the entry’s
preserved state; that is, whether they are in lockdown or set-associative TLB
regions. See “R8:TLB Operations register” on page 97 for a description of the TLB-
invalidate operations.
Victim SBZ/UNP
31 28 25 29 26 0
SBZ P
P=0 Subsequent hardware page table walks place the TLNB entry in the set associative region
of the TLB.
P=1 Subsequent hardware page table walks place the TLB entry in the lockdown region at the
entry specified by the victim, in the range 0–7.