Initial import

2 files changed, 108 insertions, 0 deletions

diff --git a/Documentation/xtensa/atomctl.txt b/Documentation/xtensa/atomctl.txt
new file mode 100644
index 000000000..1da783ac2
--- /dev/null
+++ b/Documentation/xtensa/atomctl.txt
@@ -0,0 +1,44 @@
+We Have Atomic Operation Control (ATOMCTL) Register.
+This register determines the effect of using a S32C1I instruction
+with various combinations of:
+
+     1. With and without an Coherent Cache Controller which
+        can do Atomic Transactions to the memory internally.
+
+     2. With and without An Intelligent Memory Controller which
+        can do Atomic Transactions itself.
+
+The Core comes up with a default value of for the three types of cache ops:
+
+      0x28: (WB: Internal, WT: Internal, BY:Exception)
+
+On the FPGA Cards we typically simulate an Intelligent Memory controller
+which can implement  RCW transactions. For FPGA cards with an External
+Memory controller we let it to the atomic operations internally while
+doing a Cached (WB) transaction and use the Memory RCW for un-cached
+operations.
+
+For systems without an coherent cache controller, non-MX, we always
+use the memory controllers RCW, thought non-MX controlers likely
+support the Internal Operation.
+
+CUSTOMER-WARNING:
+   Virtually all customers buy their memory controllers from vendors that
+   don't support atomic RCW memory transactions and will likely want to
+   configure this register to not use RCW.
+
+Developers might find using RCW in Bypass mode convenient when testing
+with the cache being bypassed; for example studying cache alias problems.
+
+See Section 4.3.12.4 of ISA; Bits:
+
+                             WB     WT      BY
+                           5   4 | 3   2 | 1   0
+  2 Bit
+  Field
+  Values     WB - Write Back         WT - Write Thru         BY - Bypass
+---------    ---------------         -----------------     ----------------
+    0        Exception               Exception               Exception
+    1        RCW Transaction         RCW Transaction         RCW Transaction
+    2        Internal Operation      Internal Operation      Reserved
+    3        Reserved                Reserved                Reserved
diff --git a/Documentation/xtensa/mmu.txt b/Documentation/xtensa/mmu.txt
new file mode 100644
index 000000000..0312fe664
--- /dev/null
+++ b/Documentation/xtensa/mmu.txt
@@ -0,0 +1,64 @@
+MMUv3 initialization sequence.
+
+The code in the initialize_mmu macro sets up MMUv3 memory mapping
+identically to MMUv2 fixed memory mapping. Depending on
+CONFIG_INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX symbol this code is
+located in one of the following address ranges:
+
+    0xF0000000..0xFFFFFFFF (will keep same address in MMU v2 layout;
+    			 typically ROM)
+    0x00000000..0x07FFFFFF (system RAM; this code is actually linked
+    			 at 0xD0000000..0xD7FFFFFF [cached]
+    			 or 0xD8000000..0xDFFFFFFF [uncached];
+    			 in any case, initially runs elsewhere
+    			 than linked, so have to be careful)
+
+The code has the following assumptions:
+  This code fragment is run only on an MMU v3.
+  TLBs are in their reset state.
+  ITLBCFG and DTLBCFG are zero (reset state).
+  RASID is 0x04030201 (reset state).
+  PS.RING is zero (reset state).
+  LITBASE is zero (reset state, PC-relative literals); required to be PIC.
+
+TLB setup proceeds along the following steps.
+
+  Legend:
+    VA = virtual address (two upper nibbles of it);
+    PA = physical address (two upper nibbles of it);
+    pc = physical range that contains this code;
+
+After step 2, we jump to virtual address in 0x40000000..0x5fffffff
+that corresponds to next instruction to execute in this code.
+After step 4, we jump to intended (linked) address of this code.
+
+    Step 0     Step1     Step 2     Step3     Step 4     Step5
+ ============  =====  ============  =====  ============  =====
+   VA      PA     PA    VA      PA     PA    VA      PA     PA
+ ------    --     --  ------    --     --  ------    --     --
+ E0..FF -> E0  -> E0  E0..FF -> E0         F0..FF -> F0  -> F0
+ C0..DF -> C0  -> C0  C0..DF -> C0         E0..EF -> F0  -> F0
+ A0..BF -> A0  -> A0  A0..BF -> A0         D8..DF -> 00  -> 00
+ 80..9F -> 80  -> 80  80..9F -> 80         D0..D7 -> 00  -> 00
+ 60..7F -> 60  -> 60  60..7F -> 60
+ 40..5F -> 40         40..5F -> pc  -> pc  40..5F -> pc
+ 20..3F -> 20  -> 20  20..3F -> 20
+ 00..1F -> 00  -> 00  00..1F -> 00
+
+The default location of IO peripherals is above 0xf0000000. This may change
+using a "ranges" property in a device tree simple-bus node. See ePAPR 1.1, §6.5
+for details on the syntax and semantic of simple-bus nodes. The following
+limitations apply:
+
+1. Only top level simple-bus nodes are considered
+
+2. Only one (first) simple-bus node is considered
+
+3. Empty "ranges" properties are not supported
+
+4. Only the first triplet in the "ranges" property is considered
+
+5. The parent-bus-address value is rounded down to the nearest 256MB boundary
+
+6. The IO area covers the entire 256MB segment of parent-bus-address; the
+   "ranges" triplet length field is ignored