[v3,07/11] ARC: [plat-eznps] new command line argument for HW scheduler at MTM

From: Noam Camus <noamca@mellanox.com>

We add ability for all cores at NPS SoC to control the number of cycles
HW thread can execute before it is replace with another eligible
HW thread within the same core. The replacement is done by the
HW scheduler.

Signed-off-by: Noam Camus <noamca@mellanox.com>
---
 Documentation/admin-guide/kernel-parameters.txt |    9 ++++
 arch/arc/plat-eznps/mtm.c                       |   46 ++++++++++++++++++++++-
 2 files changed, 53 insertions(+), 2 deletions(-)

On 06/15/2017 01:43 AM, Noam Camus wrote:
> From: Noam Camus <noamca@mellanox.com>
> 
> We add ability for all cores at NPS SoC to control the number of cycles
> HW thread can execute before it is replace with another eligible
> HW thread within the same core. The replacement is done by the
> HW scheduler.
> 
> Signed-off-by: Noam Camus <noamca@mellanox.com>
> ---
>   Documentation/admin-guide/kernel-parameters.txt |    9 ++++
>   arch/arc/plat-eznps/mtm.c                       |   46 ++++++++++++++++++++++-
>   2 files changed, 53 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 15f79c2..5b551f7 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2693,6 +2693,15 @@
>   			If the dependencies are under your control, you can
>   			turn on cpu0_hotplug.
>   
> +	nps_mtm_hs_ctr= [KNL,ARC]
> +			This parameter sets the maximum duration, in
> +			cycles, each HW thread of the CTOP can run
> +			without interruptions, before HW switches it.
> +			The actual maximum duration is 16 times this
> +			parameter's value.
> +			Format: integer between 1 and 255
> +			Default: 255
> +
>   	nptcg=		[IA-64] Override max number of concurrent global TLB
>   			purges which is reported from either PAL_VM_SUMMARY or
>   			SAL PALO.
> diff --git a/arch/arc/plat-eznps/mtm.c b/arch/arc/plat-eznps/mtm.c
> index dcbf8f6..9c78ad6 100644
> --- a/arch/arc/plat-eznps/mtm.c
> +++ b/arch/arc/plat-eznps/mtm.c
> @@ -21,10 +21,13 @@
>   #include <plat/mtm.h>
>   #include <plat/smp.h>
>   
> -#define MT_CTRL_HS_CNT		0xFF
> +#define MT_HS_CNT_MIN		0x01
> +#define MT_HS_CNT_MAX		0xFF
>   #define MT_CTRL_ST_CNT		0xF
>   #define NPS_NUM_HW_THREADS	0x10
>   
> +static int mtm_hs_ctr = MT_HS_CNT_MAX;
> +
>   #ifdef CONFIG_EZNPS_MEM_ERROR_ALIGN
>   int do_memory_error(unsigned long address, struct pt_regs *regs)
>   {
> @@ -127,7 +130,7 @@ void mtm_enable_core(unsigned int cpu)
>   	/* Enable HW schedule, stall counter, mtm */
>   	mt_ctrl.value = 0;
>   	mt_ctrl.hsen = 1;
> -	mt_ctrl.hs_cnt = MT_CTRL_HS_CNT;
> +	mt_ctrl.hs_cnt = mtm_hs_ctr;
>   	mt_ctrl.mten = 1;
>   	write_aux_reg(CTOP_AUX_MT_CTRL, mt_ctrl.value);
>   
> @@ -138,3 +141,42 @@ void mtm_enable_core(unsigned int cpu)
>   	 */
>   	cpu_relax();
>   }
> +
> +/* Handle an out of bounds mtm hs counter value */
> +static void __init handle_mtm_hs_ctr_out_of_bounds_error(uint8_t val)
> +{
> +	pr_err("** The value must be in range [%d,%d] (inclusive)\n",
> +		MT_HS_CNT_MIN, MT_HS_CNT_MAX);
> +
> +	mtm_hs_ctr = val;


This error handling doesn't make sense to me - if the value is not in range, why 
bother setting it at all. I'll fix it up locally.


> +}
> +
> +/* Verify and set the value of the mtm hs counter */
> +static int __init set_mtm_hs_ctr(char *ctr_str)
> +{
> +	int ret;
> +	long hs_ctr;
> +
> +	ret = kstrtol(ctr_str, 0, &hs_ctr);
> +	if (ret) {
> +		pr_err("** Out of range mtm_hs_ctr, using default value %d\n",
> +			MT_HS_CNT_MAX);
> +		mtm_hs_ctr = MT_HS_CNT_MAX;
> +		return -EINVAL;
> +	}
> +
> +	if (hs_ctr > MT_HS_CNT_MAX) {
> +		handle_mtm_hs_ctr_out_of_bounds_error(MT_HS_CNT_MAX);
> +		return -EDOM;
> +	}
> +
> +	if (hs_ctr < MT_HS_CNT_MIN) {
> +		handle_mtm_hs_ctr_out_of_bounds_error(MT_HS_CNT_MIN);
> +		return -EDOM;
> +	}
> +
> +	mtm_hs_ctr = hs_ctr;
> +
> +	return 0;
> +}
> +early_param("nps_mtm_hs_ctr", set_mtm_hs_ctr);
>

>From: Vineet Gupta [mailto:Vineet.Gupta1@synopsys.com] 
>Sent: Monday, August 21, 2017 20:04 PM
....
>> +
>> +/* Handle an out of bounds mtm hs counter value */ static void __init 
>> +handle_mtm_hs_ctr_out_of_bounds_error(uint8_t val) {
>> +	pr_err("** The value must be in range [%d,%d] (inclusive)\n",
>> +		MT_HS_CNT_MIN, MT_HS_CNT_MAX);
>> +
>> +	mtm_hs_ctr = val;


>This error handling doesn't make sense to me - if the value is not in range, why bother setting it at all. I'll fix it up locally.
Just look what we provide handle_mtm_hs_ctr_out_of_bounds_error() as parameter and it will be sensible to you :)

Noam