On 01/18/2018 05:48 AM, Alexey Brodkin wrote:
> HS48 core starts with dual-issue enabled but in some cases like
> debugging as well as benchmarking it might be useful to disable
> dual-issue for a particular run.
>
> Note:
> 1. To disable dual-issue user has to change a value of a global variable
> in target's memory right before start of Linu kernel execution
> (most probably via JTAG)
>
> 2. Disabling happens very early on boot and to get it back enabled it's
> required to restart Linux kernel. I.e. with this change we don't allow
> toggling dual-issue state in random moments of run-time
But we need access to a debugger anyways to change this global variable.
If you already have that won't it be better to change the aux register itself from
the debugger itself.
I don't really see how the global variable way of toggle adds any value here ?
>
> Signed-off-by: Alexey Brodkin <abrodkin at synopsys.com>
> ---
> arch/arc/kernel/setup.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/arch/arc/kernel/setup.c b/arch/arc/kernel/setup.c
> index 9d27331fe69a..cf97f7d88934 100644
> --- a/arch/arc/kernel/setup.c
> +++ b/arch/arc/kernel/setup.c
> @@ -31,6 +31,8 @@
>
> #define FIX_PTR(x) __asm__ __volatile__(";" : "+r"(x))
>
> +int dual_issue_enable = 1;
> +
> unsigned int intr_to_DE_cnt;
>
> /* Part of U-boot ABI: see head.S */
> @@ -198,6 +200,17 @@ static void read_arc_build_cfg_regs(void)
> if (cpu->core.family >= 0x54) {
> unsigned int exec_ctrl;
>
> + if (!dual_issue_enable) {
> + /*
> + * Note:
> + * 1) Reset value in AUX_EXEC_CTRL is 0
> + * 2) Reverse logic is used,
> + * i.e. by default (AUX_EXEC_CTRL=0)
> + * dual-issue is enabled.
> + */
> + write_aux_reg(AUX_EXEC_CTRL, 1);
> + }
> +
> READ_BCR(AUX_EXEC_CTRL, exec_ctrl);
> cpu->extn.dual_enb = !(exec_ctrl & 1);
>
