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Make mcycle/minstret inhibited by default

This commit is contained in:
Luke Wren 2021-12-12 13:55:33 +00:00
parent 2bbc3637a2
commit 8a003dbbed
4 changed files with 476 additions and 453 deletions
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908
doc/hazard3.pdf
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File diff suppressed because it is too large Load Diff

4
doc/sections/csr.adoc
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@ -310,8 +310,8 @@ Counter inhibit. Read-write. The table below lists the fields which are _not_ ha
[cols="10h,20h,~", options="header"] [cols="10h,20h,~", options="header"]
|=== |===
| Bits | Name | Description | Bits | Name | Description
| 2 | `ir` | When 1, inhibit counting of `minstret`/`minstreth` | 2 | `ir` | When 1, inhibit counting of `minstret`/`minstreth`. Resets to 1.
| 0 | `cy` | When 1, inhibit counting of `mcycle`/`mcycleh` | 0 | `cy` | When 1, inhibit counting of `mcycle`/`mcycleh`. Resets to 1.
|=== |===
==== mhpmevent3...31 ==== mhpmevent3...31

4
hdl/hazard3_csr.v
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@ -440,8 +440,8 @@ always @ (posedge clk or negedge rst_n) begin
minstreth <= X0; minstreth <= X0;
minstret <= X0; minstret <= X0;
// Counters inhibited by default to save energy // Counters inhibited by default to save energy
mcountinhibit_cy <= 1'b0; mcountinhibit_cy <= 1'b1;
mcountinhibit_ir <= 1'b0; mcountinhibit_ir <= 1'b1;
end else if (CSR_COUNTER) begin end else if (CSR_COUNTER) begin
// Optionally hold the top (2 * XLEN - W_COUNTER) bits constant to // Optionally hold the top (2 * XLEN - W_COUNTER) bits constant to
// save gates (noncompliant if enabled) // save gates (noncompliant if enabled)

13
test/sim/common/init.S
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@ -54,11 +54,20 @@ j \name
.reset_handler: .reset_handler:
la sp, __stack_top // Set counters running, as they are off by default. This may trap if counters
// mtvec LSB enables vectoring // are unimplemented, so catch the trap and continue.
la a0, 1f
csrw mtvec, a0
csrci mcountinhibit, 0x5
.p2align 2
1:
// Set up trap vector table. mtvec LSB enables vectoring
la t0, .vector_table + 1 la t0, .vector_table + 1
csrw mtvec, t0 csrw mtvec, t0
// Set up stack pointer before doing anything else
la sp, __stack_top
// newlib _start expects argc, argv on the stack. Leave stack 16-byte aligned. // newlib _start expects argc, argv on the stack. Leave stack 16-byte aligned.
addi sp, sp, -16 addi sp, sp, -16
li a0, 1 li a0, 1