Re: [PATCH] hw: timer: ibex_timer: Fixup reading w/o register

[Alistair Francis]

On Mon, Jan 10, 2022 at 3:16 PM Alistair Francis
<alistair.francis@opensource.wdc.com> wrote:
>
> From: Wilfred Mallawa <wilfred.mallawa@wdc.com>
>
> This change fixes a bug where a write only register is read.
> As per https://docs.opentitan.org/hw/ip/rv_timer/doc/#register-table
> the 'INTR_TEST0' register is write only.
>
> Signed-off-by: Wilfred Mallawa <wilfred.mallawa@wdc.com>

Thanks for the patch!

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

Alistair

> ---
>  hw/timer/ibex_timer.c         | 14 +++++---------
>  include/hw/timer/ibex_timer.h |  1 -
>  2 files changed, 5 insertions(+), 10 deletions(-)
>
> diff --git a/hw/timer/ibex_timer.c b/hw/timer/ibex_timer.c
> index 66e1f8e48c..826c38b653 100644
> --- a/hw/timer/ibex_timer.c
> +++ b/hw/timer/ibex_timer.c
> @@ -130,7 +130,6 @@ static void ibex_timer_reset(DeviceState *dev)
>      s->timer_compare_upper0 = 0xFFFFFFFF;
>      s->timer_intr_enable = 0x00000000;
>      s->timer_intr_state = 0x00000000;
> -    s->timer_intr_test = 0x00000000;
>
>      ibex_timer_update_irqs(s);
>  }
> @@ -168,7 +167,8 @@ static uint64_t ibex_timer_read(void *opaque, hwaddr addr,
>          retvalue = s->timer_intr_state;
>          break;
>      case R_INTR_TEST:
> -        retvalue = s->timer_intr_test;
> +        qemu_log_mask(LOG_GUEST_ERROR,
> +                      "Attempted to read INTR_TEST, a write only register");
>          break;
>      default:
>          qemu_log_mask(LOG_GUEST_ERROR,
> @@ -215,10 +215,7 @@ static void ibex_timer_write(void *opaque, hwaddr addr,
>          s->timer_intr_state &= ~val;
>          break;
>      case R_INTR_TEST:
> -        s->timer_intr_test = val;
> -        if (s->timer_intr_enable &
> -            s->timer_intr_test &
> -            R_INTR_ENABLE_IE_0_MASK) {
> +        if (s->timer_intr_enable & val & R_INTR_ENABLE_IE_0_MASK) {
>              s->timer_intr_state |= R_INTR_STATE_IS_0_MASK;
>              qemu_set_irq(s->irq, true);
>          }
> @@ -247,8 +244,8 @@ static int ibex_timer_post_load(void *opaque, int 
> version_id)
>
>  static const VMStateDescription vmstate_ibex_timer = {
>      .name = TYPE_IBEX_TIMER,
> -    .version_id = 1,
> -    .minimum_version_id = 1,
> +    .version_id = 2,
> +    .minimum_version_id = 2,
>      .post_load = ibex_timer_post_load,
>      .fields = (VMStateField[]) {
>          VMSTATE_UINT32(timer_ctrl, IbexTimerState),
> @@ -257,7 +254,6 @@ static const VMStateDescription vmstate_ibex_timer = {
>          VMSTATE_UINT32(timer_compare_upper0, IbexTimerState),
>          VMSTATE_UINT32(timer_intr_enable, IbexTimerState),
>          VMSTATE_UINT32(timer_intr_state, IbexTimerState),
> -        VMSTATE_UINT32(timer_intr_test, IbexTimerState),
>          VMSTATE_END_OF_LIST()
>      }
>  };
> diff --git a/include/hw/timer/ibex_timer.h b/include/hw/timer/ibex_timer.h
> index b6f69b38ee..1a0a28d5fa 100644
> --- a/include/hw/timer/ibex_timer.h
> +++ b/include/hw/timer/ibex_timer.h
> @@ -43,7 +43,6 @@ struct IbexTimerState {
>      uint32_t timer_compare_upper0;
>      uint32_t timer_intr_enable;
>      uint32_t timer_intr_state;
> -    uint32_t timer_intr_test;
>
>      uint32_t timebase_freq;
>
> --
> 2.34.1
>