Unverified Commit 747a43e8 authored by Alistair Francis's avatar Alistair Francis Committed by Palmer Dabbelt
Browse files

target/riscv: Add the mcountinhibit CSR 



1.11 defines mcountinhibit, which has the same numeric CSR value as
mucounteren from 1.09.1 but has different semantics.  This patch enables
the CSR for 1.11-based targets, which is trivial to implement because
the counters in QEMU never tick (legal according to the spec).

Signed-off-by: default avatarAlistair Francis <alistair.francis@wdc.com>
[Palmer: Fix counter access semantics, change commit message to indicate
the behavior is fully emulated.]
Reviewed-by: default avatarPalmer Dabbelt <palmer@sifive.com>
Signed-off-by: default avatarPalmer Dabbelt <palmer@sifive.com>
parent 6729dbbd

target/riscv/cpu_bits.h

+1 −0
Original line number Diff line number Diff line
@@ -136,6 +136,7 @@ 
#define CSR_MCOUNTEREN      0x306



/* Legacy Counter Setup (priv v1.9.1) */

/* Update to #define CSR_MCOUNTINHIBIT 0x320 for 1.11.0 */

#define CSR_MUCOUNTEREN     0x320

#define CSR_MSCOUNTEREN     0x321

#define CSR_MHCOUNTEREN     0x322

target/riscv/csr.c

+15 −2
Original line number Diff line number Diff line
@@ -56,6 +56,15 @@ static int fs(CPURISCVState *env, int csrno) 
static int ctr(CPURISCVState *env, int csrno)

{

#if !defined(CONFIG_USER_ONLY)

    /*

     * The counters are always enabled on newer priv specs, as the CSR has

     * changed from controlling that the counters can be read to controlling

     * that the counters increment.

     */

    if (env->priv_ver > PRIV_VERSION_1_09_1) {

        return 0;

    }



    uint32_t ctr_en = ~0u;



    if (env->priv < PRV_M) {
@@ -461,18 +470,22 @@ static int write_mcounteren(CPURISCVState *env, int csrno, target_ulong val) 
    return 0;

}



/* This regiser is replaced with CSR_MCOUNTINHIBIT in 1.11.0 */

static int read_mscounteren(CPURISCVState *env, int csrno, target_ulong *val)

{

    if (env->priv_ver > PRIV_VERSION_1_09_1) {

    if (env->priv_ver > PRIV_VERSION_1_09_1

        && env->priv_ver < PRIV_VERSION_1_11_0) {

        return -1;

    }

    *val = env->mcounteren;

    return 0;

}



/* This regiser is replaced with CSR_MCOUNTINHIBIT in 1.11.0 */

static int write_mscounteren(CPURISCVState *env, int csrno, target_ulong val)

{

    if (env->priv_ver > PRIV_VERSION_1_09_1) {

    if (env->priv_ver > PRIV_VERSION_1_09_1

        && env->priv_ver < PRIV_VERSION_1_11_0) {

        return -1;

    }

    env->mcounteren = val;