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Re: [PATCH v3 3/9] target/riscv: Add the lowRISC Ibex CPU

From: LIU Zhiwei
Subject: Re: [PATCH v3 3/9] target/riscv: Add the lowRISC Ibex CPU
Date: Wed, 27 May 2020 09:58:27 +0800
User-agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.8.1

On 2020/5/27 1:12, Alistair Francis wrote:
On Fri, May 22, 2020 at 12:51 AM LIU Zhiwei <address@hidden> wrote:

On 2020/5/20 5:31, Alistair Francis wrote:
Ibex is a small and efficient, 32-bit, in-order RISC-V core with
a 2-stage pipeline that implements the RV32IMC instruction set

For more details on lowRISC see here:

Signed-off-by: Alistair Francis <address@hidden>
Reviewed-by: Bin Meng <address@hidden>
   target/riscv/cpu.h |  1 +
   target/riscv/cpu.c | 10 ++++++++++
   2 files changed, 11 insertions(+)

diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index d0e7f5b9c5..8733d7467f 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -35,6 +35,7 @@
   #define TYPE_RISCV_CPU_ANY              RISCV_CPU_TYPE_NAME("any")
   #define TYPE_RISCV_CPU_BASE32           RISCV_CPU_TYPE_NAME("rv32")
   #define TYPE_RISCV_CPU_BASE64           RISCV_CPU_TYPE_NAME("rv64")
+#define TYPE_RISCV_CPU_IBEX             RISCV_CPU_TYPE_NAME("lowrisc-ibex")
   #define TYPE_RISCV_CPU_SIFIVE_E31       RISCV_CPU_TYPE_NAME("sifive-e31")
   #define TYPE_RISCV_CPU_SIFIVE_E34       RISCV_CPU_TYPE_NAME("sifive-e34")
   #define TYPE_RISCV_CPU_SIFIVE_E51       RISCV_CPU_TYPE_NAME("sifive-e51")
diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 5eb3c02735..eb2bbc87ae 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -156,6 +156,15 @@ static void rv32gcsu_priv1_10_0_cpu_init(Object *obj)
       set_feature(env, RISCV_FEATURE_PMP);

+static void rv32imcu_nommu_cpu_init(Object *obj)
+    CPURISCVState *env = &RISCV_CPU(obj)->env;
+    set_misa(env, RV32 | RVI | RVM | RVC | RVU);
+    set_priv_version(env, PRIV_VERSION_1_10_0);
+    set_resetvec(env, 0x8090);
Hi Alistair,

I see all RISC-V cpus  have an reset vector which acts as the first pc
when machine boots up.
However, the first pc is more like an attribute of a machine, not a cpu.
In general it seems to be a CPU property. I assume that some CPUs
would allow the reset vector to be selectable though, in which case it
becomes a board property.

Another reason is that the cpu names are a combination of ISA.
Then the cpus from different vendors may have same ISA, with different
reset vectors.

Do you think so?
If you are worried about CPUs with different vectors we could always
make it a property in the future and have boards override it. I don't
think we need that yet (only 1 CPU is different) but it is an easy
future change.
I think your are right. A cpu reset vector property is better. If there is a conflict in the future,
we can add the property there.

Reviewed-by: LIU Zhiwei <address@hidden>


+    set_feature(env, RISCV_FEATURE_PMP);
   static void rv32imacu_nommu_cpu_init(Object *obj)
       CPURISCVState *env = &RISCV_CPU(obj)->env;
@@ -619,6 +628,7 @@ static const TypeInfo riscv_cpu_type_infos[] = {
       DEFINE_CPU(TYPE_RISCV_CPU_ANY,              riscv_any_cpu_init),
   #if defined(TARGET_RISCV32)
       DEFINE_CPU(TYPE_RISCV_CPU_BASE32,           riscv_base32_cpu_init),
+    DEFINE_CPU(TYPE_RISCV_CPU_IBEX,             rv32imcu_nommu_cpu_init),
       DEFINE_CPU(TYPE_RISCV_CPU_SIFIVE_E31,       rv32imacu_nommu_cpu_init),
       DEFINE_CPU(TYPE_RISCV_CPU_SIFIVE_E34,       rv32imafcu_nommu_cpu_init),

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