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Date: Tue, 17 May 2022 09:55:10 +0900
From: Stafford Horne <shorne@...il.com>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Openrisc <openrisc@...ts.librecores.org>,
Stafford Horne <shorne@...il.com>,
Jonas Bonn <jonas@...thpole.se>,
Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
Randy Dunlap <rdunlap@...radead.org>
Subject: [PATCH v2 13/13] openrisc: Remove unused IMMU tlb workardound
This looks to be some historical code that was used to convert TLB
misses on branches from l.bf, l.jal, l.j etc all to a trampoline
using l.jr (jump register). I don't see this being used and I don't
know the history of it so remove it.
Signed-off-by: Stafford Horne <shorne@...il.com>
---
arch/openrisc/kernel/head.S | 209 ------------------------------------
1 file changed, 209 deletions(-)
diff --git a/arch/openrisc/kernel/head.S b/arch/openrisc/kernel/head.S
index 21db50563f97..9b59d0ca665c 100644
--- a/arch/openrisc/kernel/head.S
+++ b/arch/openrisc/kernel/head.S
@@ -1325,215 +1325,6 @@ i_pte_not_present:
/* =================================================[ debugging aids ]=== */
- .align 64
-_immu_trampoline:
- .space 64
-_immu_trampoline_top:
-
-#define TRAMP_SLOT_0 (0x0)
-#define TRAMP_SLOT_1 (0x4)
-#define TRAMP_SLOT_2 (0x8)
-#define TRAMP_SLOT_3 (0xc)
-#define TRAMP_SLOT_4 (0x10)
-#define TRAMP_SLOT_5 (0x14)
-#define TRAMP_FRAME_SIZE (0x18)
-
-ENTRY(_immu_trampoline_workaround)
- // r2 EEA
- // r6 is physical EEA
- tophys(r6,r2)
-
- LOAD_SYMBOL_2_GPR(r5,_immu_trampoline)
- tophys (r3,r5) // r3 is trampoline (physical)
-
- LOAD_SYMBOL_2_GPR(r4,0x15000000)
- l.sw TRAMP_SLOT_0(r3),r4
- l.sw TRAMP_SLOT_1(r3),r4
- l.sw TRAMP_SLOT_4(r3),r4
- l.sw TRAMP_SLOT_5(r3),r4
-
- // EPC = EEA - 0x4
- l.lwz r4,0x0(r6) // load op @ EEA + 0x0 (fc address)
- l.sw TRAMP_SLOT_3(r3),r4 // store it to _immu_trampoline_data
- l.lwz r4,-0x4(r6) // load op @ EEA - 0x4 (f8 address)
- l.sw TRAMP_SLOT_2(r3),r4 // store it to _immu_trampoline_data
-
- l.srli r5,r4,26 // check opcode for write access
- l.sfeqi r5,0 // l.j
- l.bf 0f
- l.sfeqi r5,0x11 // l.jr
- l.bf 1f
- l.sfeqi r5,1 // l.jal
- l.bf 2f
- l.sfeqi r5,0x12 // l.jalr
- l.bf 3f
- l.sfeqi r5,3 // l.bnf
- l.bf 4f
- l.sfeqi r5,4 // l.bf
- l.bf 5f
-99:
- l.nop
- l.j 99b // should never happen
- l.nop 1
-
- // r2 is EEA
- // r3 is trampoline address (physical)
- // r4 is instruction
- // r6 is physical(EEA)
- //
- // r5
-
-2: // l.jal
-
- /* 19 20 aa aa l.movhi r9,0xaaaa
- * a9 29 bb bb l.ori r9,0xbbbb
- *
- * where 0xaaaabbbb is EEA + 0x4 shifted right 2
- */
-
- l.addi r6,r2,0x4 // this is 0xaaaabbbb
-
- // l.movhi r9,0xaaaa
- l.ori r5,r0,0x1920 // 0x1920 == l.movhi r9
- l.sh (TRAMP_SLOT_0+0x0)(r3),r5
- l.srli r5,r6,16
- l.sh (TRAMP_SLOT_0+0x2)(r3),r5
-
- // l.ori r9,0xbbbb
- l.ori r5,r0,0xa929 // 0xa929 == l.ori r9
- l.sh (TRAMP_SLOT_1+0x0)(r3),r5
- l.andi r5,r6,0xffff
- l.sh (TRAMP_SLOT_1+0x2)(r3),r5
-
- /* falthrough, need to set up new jump offset */
-
-
-0: // l.j
- l.slli r6,r4,6 // original offset shifted left 6 - 2
-// l.srli r6,r6,6 // original offset shifted right 2
-
- l.slli r4,r2,4 // old jump position: EEA shifted left 4
-// l.srli r4,r4,6 // old jump position: shifted right 2
-
- l.addi r5,r3,0xc // new jump position (physical)
- l.slli r5,r5,4 // new jump position: shifted left 4
-
- // calculate new jump offset
- // new_off = old_off + (old_jump - new_jump)
-
- l.sub r5,r4,r5 // old_jump - new_jump
- l.add r5,r6,r5 // orig_off + (old_jump - new_jump)
- l.srli r5,r5,6 // new offset shifted right 2
-
- // r5 is new jump offset
- // l.j has opcode 0x0...
- l.sw TRAMP_SLOT_2(r3),r5 // write it back
-
- l.j trampoline_out
- l.nop
-
-/* ----------------------------- */
-
-3: // l.jalr
-
- /* 19 20 aa aa l.movhi r9,0xaaaa
- * a9 29 bb bb l.ori r9,0xbbbb
- *
- * where 0xaaaabbbb is EEA + 0x4 shifted right 2
- */
-
- l.addi r6,r2,0x4 // this is 0xaaaabbbb
-
- // l.movhi r9,0xaaaa
- l.ori r5,r0,0x1920 // 0x1920 == l.movhi r9
- l.sh (TRAMP_SLOT_0+0x0)(r3),r5
- l.srli r5,r6,16
- l.sh (TRAMP_SLOT_0+0x2)(r3),r5
-
- // l.ori r9,0xbbbb
- l.ori r5,r0,0xa929 // 0xa929 == l.ori r9
- l.sh (TRAMP_SLOT_1+0x0)(r3),r5
- l.andi r5,r6,0xffff
- l.sh (TRAMP_SLOT_1+0x2)(r3),r5
-
- l.lhz r5,(TRAMP_SLOT_2+0x0)(r3) // load hi part of jump instruction
- l.andi r5,r5,0x3ff // clear out opcode part
- l.ori r5,r5,0x4400 // opcode changed from l.jalr -> l.jr
- l.sh (TRAMP_SLOT_2+0x0)(r3),r5 // write it back
-
- /* falthrough */
-
-1: // l.jr
- l.j trampoline_out
- l.nop
-
-/* ----------------------------- */
-
-4: // l.bnf
-5: // l.bf
- l.slli r6,r4,6 // original offset shifted left 6 - 2
-// l.srli r6,r6,6 // original offset shifted right 2
-
- l.slli r4,r2,4 // old jump position: EEA shifted left 4
-// l.srli r4,r4,6 // old jump position: shifted right 2
-
- l.addi r5,r3,0xc // new jump position (physical)
- l.slli r5,r5,4 // new jump position: shifted left 4
-
- // calculate new jump offset
- // new_off = old_off + (old_jump - new_jump)
-
- l.add r6,r6,r4 // (orig_off + old_jump)
- l.sub r6,r6,r5 // (orig_off + old_jump) - new_jump
- l.srli r6,r6,6 // new offset shifted right 2
-
- // r6 is new jump offset
- l.lwz r4,(TRAMP_SLOT_2+0x0)(r3) // load jump instruction
- l.srli r4,r4,16
- l.andi r4,r4,0xfc00 // get opcode part
- l.slli r4,r4,16
- l.or r6,r4,r6 // l.b(n)f new offset
- l.sw TRAMP_SLOT_2(r3),r6 // write it back
-
- /* we need to add l.j to EEA + 0x8 */
- tophys (r4,r2) // may not be needed (due to shifts down_
- l.addi r4,r4,(0x8 - 0x8) // jump target = r2 + 0x8 (compensate for 0x8)
- // jump position = r5 + 0x8 (0x8 compensated)
- l.sub r4,r4,r5 // jump offset = target - new_position + 0x8
-
- l.slli r4,r4,4 // the amount of info in imediate of jump
- l.srli r4,r4,6 // jump instruction with offset
- l.sw TRAMP_SLOT_4(r3),r4 // write it to 4th slot
-
- /* fallthrough */
-
-trampoline_out:
- // set up new EPC to point to our trampoline code
- LOAD_SYMBOL_2_GPR(r5,_immu_trampoline)
- l.mtspr r0,r5,SPR_EPCR_BASE
-
- // immu_trampoline is (4x) CACHE_LINE aligned
- // and only 6 instructions long,
- // so we need to invalidate only 2 lines
-
- /* Establish cache block size
- If BS=0, 16;
- If BS=1, 32;
- r14 contain block size
- */
- l.mfspr r21,r0,SPR_ICCFGR
- l.andi r21,r21,SPR_ICCFGR_CBS
- l.srli r21,r21,7
- l.ori r23,r0,16
- l.sll r14,r23,r21
-
- l.mtspr r0,r5,SPR_ICBIR
- l.add r5,r5,r14
- l.mtspr r0,r5,SPR_ICBIR
-
- l.jr r9
- l.nop
-
/*
* DESC: Prints ASCII character stored in r7
*
--
2.31.1
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