[PATCH v3 04/16] arm_mpam: propagate MSC read errors for mpam_msc_read_mbwu_l()

[Andre Przywara <andre.przywara@arm.com>]

Allow the mpam_msc_read_mbwu_l() function to return an error, and
propagate read errors from the lower level up.
So far we were using a special value to indicate the "unstable read"
condition, replace that with the actual Linux error code, since it's now
easy to do.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
---
 drivers/resctrl/mpam_devices.c | 54 +++++++++++++++++++++++++---------
 1 file changed, 40 insertions(+), 14 deletions(-)

diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index b1bd047da203..3b6f9e552a9f 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -1112,8 +1112,9 @@ static bool mpam_ris_has_mbwu_long_counter(struct mpam_msc_ris *ris)
 		mpam_has_feature(mpam_feat_msmon_mbwu_44counter, &ris->props));
 }
 
-static u64 mpam_msc_read_mbwu_l(struct mpam_msc *msc)
+static int mpam_msc_read_mbwu_l(struct mpam_msc *msc, u64 *res)
 {
+	int ret;
 	int retry = 3;
 	u32 mbwu_l_low;
 	u32 mbwu_l_high1, mbwu_l_high2;
@@ -1123,20 +1124,30 @@ static u64 mpam_msc_read_mbwu_l(struct mpam_msc *msc)
 	WARN_ON_ONCE((MSMON_MBWU_L + sizeof(u64)) > msc->mapped_hwpage_sz);
 	WARN_ON_ONCE(!cpumask_test_cpu(smp_processor_id(), &msc->accessibility));
 
-	__mpam_read_reg(msc, MSMON_MBWU_L + 4, &mbwu_l_high2);
+	ret = __mpam_read_reg(msc, MSMON_MBWU_L + 4, &mbwu_l_high2);
+	if (ret)
+		return ret;
+
 	do {
 		mbwu_l_high1 = mbwu_l_high2;
-		__mpam_read_reg(msc, MSMON_MBWU_L, &mbwu_l_low);
-		__mpam_read_reg(msc, MSMON_MBWU_L + 4, &mbwu_l_high2);
+		ret = __mpam_read_reg(msc, MSMON_MBWU_L, &mbwu_l_low);
+		if (ret)
+			return ret;
+		ret = __mpam_read_reg(msc, MSMON_MBWU_L + 4, &mbwu_l_high2);
+		if (ret)
+			return ret;
 
 		retry--;
 	} while (mbwu_l_high1 != mbwu_l_high2 && retry > 0);
 
-	if (mbwu_l_high1 == mbwu_l_high2)
-		return ((u64)mbwu_l_high1 << 32) | mbwu_l_low;
+	if (mbwu_l_high1 == mbwu_l_high2) {
+		*res = ((u64)mbwu_l_high1 << 32) | mbwu_l_low;
+	} else {
+		pr_warn("Failed to read a stable value\n");
+		ret = -EBUSY;
+	}
 
-	pr_warn("Failed to read a stable value\n");
-	return MSMON___L_NRDY;
+	return ret;
 }
 
 static void mpam_msc_zero_mbwu_l(struct mpam_msc *msc)
@@ -1283,6 +1294,7 @@ static u64 mpam_msmon_overflow_val(enum mpam_device_features type,
 static void __ris_msmon_read(void *arg)
 {
 	u64 now;
+	int ret;
 	u32 now32;
 	bool nrdy = false;
 	bool config_mismatch;
@@ -1358,8 +1370,9 @@ static void __ris_msmon_read(void *arg)
 	case mpam_feat_msmon_mbwu_44counter:
 	case mpam_feat_msmon_mbwu_63counter:
 		if (m->type != mpam_feat_msmon_mbwu_31counter) {
-			now = mpam_msc_read_mbwu_l(msc);
-			nrdy = now & MSMON___L_NRDY;
+			ret = mpam_msc_read_mbwu_l(msc, &now);
+			if (ret)
+				goto out_unlock;
 
 			if (m->type == mpam_feat_msmon_mbwu_63counter)
 				now = FIELD_GET(MSMON___LWD_VALUE, now);
@@ -1397,10 +1410,15 @@ static void __ris_msmon_read(void *arg)
 	if (nrdy)
 		m->err = -EBUSY;
 
-	if (m->err)
-		return;
+	if (!m->err)
+		*m->val += now;
+
+	return;
+
+out_unlock:
+	mpam_mon_sel_unlock(msc);
 
-	*m->val += now;
+	m->err = ret;
 }
 
 static int _msmon_read(struct mpam_component *comp, struct mon_read *arg)
@@ -1747,6 +1765,7 @@ static int mpam_save_mbwu_state(void *arg)
 {
 	int i;
 	u64 val;
+	int ret = 0;
 	struct mon_cfg *cfg;
 	u32 cur_flt, cur_ctl, mon_sel;
 	struct mpam_msc_ris *ris = arg;
@@ -1768,7 +1787,9 @@ static int mpam_save_mbwu_state(void *arg)
 		mpam_write_monsel_reg(msc, CFG_MBWU_CTL, 0);
 
 		if (mpam_ris_has_mbwu_long_counter(ris)) {
-			val = mpam_msc_read_mbwu_l(msc);
+			ret = mpam_msc_read_mbwu_l(msc, &val);
+			if (ret)
+				goto out_unlock;
 			mpam_msc_zero_mbwu_l(msc);
 		} else {
 			u32 val32;
@@ -1788,6 +1809,11 @@ static int mpam_save_mbwu_state(void *arg)
 	}
 
 	return 0;
+
+out_unlock:
+	mpam_mon_sel_unlock(msc);
+
+	return ret;
 }
 
 /*
-- 
2.43.0