Commit 5d0fa28f authored by Zeng Heng's avatar Zeng Heng
Browse files

arm64/mpam: Improve conversion accuracy between percent and fixed-point fraction 

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IAKAKN



--------------------------------

According to the bit width of the fixed-point fraction implemented by
hardware, the maximum supported precision is calculated to reduce the
conversion granularity as much as possible, so that improving conversion
accuracy between percent and fixed-point fraction.

Fixes: 58db5c68 ("untested: arm_mpam: resctrl: Add support for MB resource")
Signed-off-by: default avatarZeng Heng <zengheng4@huawei.com>
parent dbb48097

drivers/platform/mpam/mpam_resctrl.c

+26 −14
Original line number Diff line number Diff line
@@ -536,21 +536,31 @@ static u32 mbw_pbm_to_percent(unsigned long mbw_pbm, struct mpam_props *cprops) 
	return result;

}



static u32 mbw_max_to_percent(u16 mbw_max, struct mpam_props *cprops)

static int get_wd_precision(u8 wd)

{

	int ret = (1 << wd) / MAX_MBA_BW;



	if (!ret)

		return 1;



	return ret;

}



static u32 mbw_max_to_percent(u16 mbw_max, u8 wd)

{

	u8 bit;

	u32 divisor = 2, value = 0;

	u32 divisor = 2, value = 0, precision = get_wd_precision(wd);



	for (bit = 15; bit; bit--) {

		if (mbw_max & BIT(bit))

			value += MAX_MBA_BW / divisor;

			value += MAX_MBA_BW * precision / divisor;

		divisor <<= 1;

	}



	return value;

	return DIV_ROUND_UP(value, precision);

}



static u32 percent_to_mbw_pbm(u8 pc, struct mpam_props *cprops)

static u32 percent_to_mbw_pbm(u32 pc, struct mpam_props *cprops)

{

	u32 granularity = get_mba_granularity(cprops);

	u8 num_bits = pc / granularity;
@@ -562,26 +572,28 @@ static u32 percent_to_mbw_pbm(u8 pc, struct mpam_props *cprops) 
	return (1 << num_bits) - 1;

}



static u16 percent_to_mbw_max(u8 pc, struct mpam_props *cprops)

static u16 percent_to_mbw_max(u32 pc, u8 wd)

{

	u8 bit;

	u32 divisor = 2, value = 0;

	u32 divisor = 2, value = 0, precision = get_wd_precision(wd);



	if (WARN_ON_ONCE(cprops->bwa_wd > 15))

	if (WARN_ON_ONCE(wd > 15))

		return MAX_MBA_BW;



	pc *= precision;



	for (bit = 15; bit; bit--) {

		if (pc >= MAX_MBA_BW / divisor) {

			pc -= MAX_MBA_BW / divisor;

		if (pc >= MAX_MBA_BW * precision / divisor) {

			pc -= MAX_MBA_BW * precision / divisor;

			value |= BIT(bit);

		}

		divisor <<= 1;



		if (!pc || !(MAX_MBA_BW / divisor))

		if (!pc || !(MAX_MBA_BW * precision / divisor))

			break;

	}



	value &= GENMASK(15, 15 - cprops->bwa_wd + 1);

	value &= GENMASK(15, 15 - wd + 1);



	return value;

}
@@ -947,7 +959,7 @@ u32 resctrl_arch_get_config(struct rdt_resource *r, struct rdt_domain *d, 
		/* TODO: Scaling is not yet supported */

		return mbw_pbm_to_percent(cfg->mbw_pbm, cprops);

	case mpam_feat_mbw_max:

		return mbw_max_to_percent(cfg->mbw_max, cprops);

		return mbw_max_to_percent(cfg->mbw_max, cprops->bwa_wd);

	default:

		return -EINVAL;

	}
@@ -989,7 +1001,7 @@ int resctrl_arch_update_one(struct rdt_resource *r, struct rdt_domain *d, 
			mpam_set_feature(mpam_feat_mbw_part, &cfg);

			break;

		} else if (mpam_has_feature(mpam_feat_mbw_max, cprops)) {

			cfg.mbw_max = percent_to_mbw_max(cfg_val, cprops);

			cfg.mbw_max = percent_to_mbw_max(cfg_val, cprops->bwa_wd);

			mpam_set_feature(mpam_feat_mbw_max, &cfg);

			break;

		}