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Feature/privil mode spec update (#96)

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* [rtl] Clear mprv on mret to non M-mode

This is specification change between the v1.11 and v1.12 privileged
architectures. Previously mprv wasn't altered on mret. Now if returning
to a privilege level other than M mode mprv must be cleared.

* [rtl, dv] Add new CSRs for latest priviledged spec

This adds the following CSRs to support the v1.12 priviledged spec.

 - MSTATUSH
 - MCONFIGPTR
 - MENVCFG
 - MENVCFGH

MCONFIGPTR is read only and has its value provided by a ibex_pkg
parameter CSR_MCONFIGPTR_VALUE which is set to 0. Implementors can alter
this value if needed.

All the other CSRs ignore writes and read as 0.

---------

Co-authored-by: Greg Chadwick <gac@lowrisc.org>
This commit is contained in:
christian-herber-nxp 2023-03-03 17:18:30 +01:00 • committed by GitHub
parent 823f596047
commit 685f1f6ee7
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GPG key ID: 4AEE18F83AFDEB23
2 changed files with 28 additions and 4 deletions
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13
rtl/cve2_cs_registers.sv
View file

@ -279,6 +279,8 @@ module cve2_cs_registers #(
CSR_MIMPID: csr_rdata_int = CSR_MIMPID_VALUE;
// mhartid: unique hardware thread id
CSR_MHARTID: csr_rdata_int = hart_id_i;
// mconfigptr: pointer to configuration data structre
CSR_MCONFIGPTR: csr_rdata_int = CSR_MCONFIGPTR_VALUE;
// mstatus: always M-mode, contains IE bit
CSR_MSTATUS: begin
@ -290,6 +292,13 @@ module cve2_cs_registers #(
csr_rdata_int[CSR_MSTATUS_TW_BIT] = mstatus_q.tw;
end
// mstatush: All zeros for Ibex (fixed little endian and all other bits reserved)
CSR_MSTATUSH: csr_rdata_int = '0;
// menvcfg: machine environment configuration, all zeros for Ibex (none of the relevant
// features are implemented)
CSR_MENVCFG, CSR_MENVCFGH: csr_rdata_int = '0;
// misa
CSR_MISA: csr_rdata_int = MISA_VALUE;
@ -663,6 +672,10 @@ module cve2_cs_registers #(
mstatus_en = 1'b1;
mstatus_d.mie = mstatus_q.mpie; // re-enable interrupts
if (mstatus_q.mpp != PRIV_LVL_M) begin
mstatus_d.mprv = 1'b0;
end
// SEC_CM: EXCEPTION.CTRL_FLOW.LOCAL_ESC
// SEC_CM: EXCEPTION.CTRL_FLOW.GLOBAL_ESC

19
rtl/cve2_pkg.sv
View file

@ -364,10 +364,11 @@ package cve2_pkg;
// CSRs
typedef enum logic[11:0] {
// Machine information
CSR_MVENDORID = 12'hF11,
CSR_MARCHID = 12'hF12,
CSR_MIMPID = 12'hF13,
CSR_MHARTID = 12'hF14,
CSR_MVENDORID = 12'hF11,
CSR_MARCHID = 12'hF12,
CSR_MIMPID = 12'hF13,
CSR_MHARTID = 12'hF14,
CSR_MCONFIGPTR = 12'hF15,
// Machine trap setup
CSR_MSTATUS = 12'h300,
@ -375,6 +376,10 @@ package cve2_pkg;
CSR_MIE = 12'h304,
CSR_MTVEC = 12'h305,
CSR_MCOUNTEREN= 12'h306,
CSR_MSTATUSH = 12'h310,
CSR_MENVCFG = 12'h30A,
CSR_MENVCFGH = 12'h31A,
// Machine trap handling
CSR_MSCRATCH = 12'h340,
@ -565,5 +570,11 @@ package cve2_pkg;
// version here using their own unique encoding (e.g. 32 bits of the git hash of the implemented
// commit).
localparam logic [31:0] CSR_MIMPID_VALUE = 32'b0;
// Machine Configuration Pointer
// 0 indicates the configuration data structure does not eixst. Ibex implementors may wish to
// alter this to point to their system specific configuration data structure.
localparam logic [31:0] CSR_MCONFIGPTR_VALUE = 32'b0;
endpackage