powerpc/perf: Adds support for programming of Thresholding in P10

Thresholding, a performance monitoring unit feature, can be
used to identify marked instructions which take more than
expected cycles between start event and end event.
Threshold compare (thresh_cmp) bits are programmed in MMCRA
register. In Power9, thresh_cmp bits were part of the
event code. But in case of P10, thresh_cmp are not part of
event code due to inclusion of MMCR3 bits.

Patch here adds an option to use attr.config1 variable
to be used to pass thresh_cmp value to be programmed in
MMCRA register. A new ppmu flag called PPMU_HAS_ATTR_CONFIG1
has been added and this flag is used to notify the use of
attr.config1 variable.

Patch has extended the parameter list of 'compute_mmcr',
to include power_pmu's 'flags' element and parameter list of
get_constraint to include attr.config1 value. It also extend
parameter list of power_check_constraints inorder to pass
perf_event list.

As stated by commit ef0e3b650f8d ("powerpc/perf: Fix Threshold
Event Counter Multiplier width for P10"), constraint bits for
thresh_cmp is also needed to be increased to 11 bits, which is
handled as part of this patch. We added bit number 53 as part
of constraint bits of thresh_cmp for power10 to make it an
11 bit field.

Updated layout for p10:

/*
 * Layout of constraint bits:
 *
 *        60        56        52        48        44        40        36        32
 * | - - - - | - - - - | - - - - | - - - - | - - - - | - - - - | - - - - | - - - - |
 *   [   fab_match   ]         [       thresh_cmp      ] [   thresh_ctl    ] [   ]
 *                                          |                                  |
 *                           [  thresh_cmp bits for p10]           thresh_sel -*
 *
 *        28        24        20        16        12         8         4         0
 * | - - - - | - - - - | - - - - | - - - - | - - - - | - - - - | - - - - | - - - - |
 *               [ ] |   [ ] |  [  sample ]   [     ]   [6] [5]   [4] [3]   [2] [1]
 *                |  |    |  |                  |
 *      BHRB IFM -*  |    |  |*radix_scope      |      Count of events for each PMC.
 *              EBB -*    |                     |        p1, p2, p3, p4, p5, p6.
 *      L1 I/D qualifier -*                     |
 *                     nc - number of counters -*
 *
 * The PMC fields P1..P6, and NC, are adder fields. As we accumulate constraints
 * we want the low bit of each field to be added to any existing value.
 *
 * Everything else is a value field.
 */

Result:
command#: cat /sys/devices/cpu/format/thresh_cmp
config1:0-17

ex. usage:

command#: perf record -I --weight -d  -e
	 cpu/event=0x67340101EC,thresh_cmp=500/ ./ebizzy -S 2 -t 1 -s 4096
1826636 records/s
real  2.00 s
user  2.00 s
sys   0.00 s
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.038 MB perf.data (61 samples) ]

Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210209095234.837356-1-kjain@linux.ibm.com

1 files changed, 59 insertions, 8 deletions

diff --git a/arch/powerpc/perf/isa207-common.c b/arch/powerpc/perf/isa207-common.c
index 6ab5b272090a..e4f577da33d8 100644
--- a/arch/powerpc/perf/isa207-common.c
+++ b/arch/powerpc/perf/isa207-common.c
@@ -108,12 +108,57 @@ static void mmcra_sdar_mode(u64 event, unsigned long *mmcra)
 		*mmcra |= MMCRA_SDAR_MODE_TLB;
 }
 
+static u64 p10_thresh_cmp_val(u64 value)
+{
+	int exp = 0;
+	u64 result = value;
+
+	if (!value)
+		return value;
+
+	/*
+	 * Incase of P10, thresh_cmp value is not part of raw event code
+	 * and provided via attr.config1 parameter. To program threshold in MMCRA,
+	 * take a 18 bit number N and shift right 2 places and increment
+	 * the exponent E by 1 until the upper 10 bits of N are zero.
+	 * Write E to the threshold exponent and write the lower 8 bits of N
+	 * to the threshold mantissa.
+	 * The max threshold that can be written is 261120.
+	 */
+	if (cpu_has_feature(CPU_FTR_ARCH_31)) {
+		if (value > 261120)
+			value = 261120;
+		while ((64 - __builtin_clzl(value)) > 8) {
+			exp++;
+			value >>= 2;
+		}
+
+		/*
+		 * Note that it is invalid to write a mantissa with the
+		 * upper 2 bits of mantissa being zero, unless the
+		 * exponent is also zero.
+		 */
+		if (!(value & 0xC0) && exp)
+			result = 0;
+		else
+			result = (exp << 8) | value;
+	}
+	return result;
+}
+
 static u64 thresh_cmp_val(u64 value)
 {
+	if (cpu_has_feature(CPU_FTR_ARCH_31))
+		value = p10_thresh_cmp_val(value);
+
+	/*
+	 * Since location of threshold compare bits in MMCRA
+	 * is different for p8, using different shift value.
+	 */
 	if (cpu_has_feature(CPU_FTR_ARCH_300))
 		return value << p9_MMCRA_THR_CMP_SHIFT;
-
-	return value << MMCRA_THR_CMP_SHIFT;
+	else
+		return value << MMCRA_THR_CMP_SHIFT;
 }
 
 static unsigned long combine_from_event(u64 event)
@@ -141,13 +186,13 @@ static bool is_thresh_cmp_valid(u64 event)
 {
 	unsigned int cmp, exp;
 
+	if (cpu_has_feature(CPU_FTR_ARCH_31))
+		return p10_thresh_cmp_val(event) != 0;
+
 	/*
 	 * Check the mantissa upper two bits are not zero, unless the
 	 * exponent is also zero. See the THRESH_CMP_MANTISSA doc.
-	 * Power10: thresh_cmp is replaced by l2_l3 event select.
 	 */
-	if (cpu_has_feature(CPU_FTR_ARCH_31))
-		return false;
 
 	cmp = (event >> EVENT_THR_CMP_SHIFT) & EVENT_THR_CMP_MASK;
 	exp = cmp >> 7;
@@ -256,7 +301,7 @@ void isa207_get_mem_weight(u64 *weight)
 		*weight = mantissa << (2 * exp);
 }
 
-int isa207_get_constraint(u64 event, unsigned long *maskp, unsigned long *valp)
+int isa207_get_constraint(u64 event, unsigned long *maskp, unsigned long *valp, u64 event_config1)
 {
 	unsigned int unit, pmc, cache, ebb;
 	unsigned long mask, value;
@@ -355,9 +400,11 @@ int isa207_get_constraint(u64 event, unsigned long *maskp, unsigned long *valp)
 	}
 
 	if (cpu_has_feature(CPU_FTR_ARCH_31)) {
-		if (event_is_threshold(event)) {
+		if (event_is_threshold(event) && is_thresh_cmp_valid(event_config1)) {
 			mask  |= CNST_THRESH_CTL_SEL_MASK;
 			value |= CNST_THRESH_CTL_SEL_VAL(event >> EVENT_THRESH_SHIFT);
+			mask  |= p10_CNST_THRESH_CMP_MASK;
+			value |= p10_CNST_THRESH_CMP_VAL(p10_thresh_cmp_val(event_config1));
 		}
 	} else if (cpu_has_feature(CPU_FTR_ARCH_300))  {
 		if (event_is_threshold(event) && is_thresh_cmp_valid(event)) {
@@ -411,7 +458,7 @@ ebb_bhrb:
 
 int isa207_compute_mmcr(u64 event[], int n_ev,
 			       unsigned int hwc[], struct mmcr_regs *mmcr,
-			       struct perf_event *pevents[])
+			       struct perf_event *pevents[], u32 flags)
 {
 	unsigned long mmcra, mmcr1, mmcr2, unit, combine, psel, cache, val;
 	unsigned long mmcr3;
@@ -504,6 +551,10 @@ int isa207_compute_mmcr(u64 event[], int n_ev,
 				val = (event[i] >> EVENT_THR_CMP_SHIFT) &
 					EVENT_THR_CMP_MASK;
 				mmcra |= thresh_cmp_val(val);
+			} else if (flags & PPMU_HAS_ATTR_CONFIG1) {
+				val = (pevents[i]->attr.config1 >> p10_EVENT_THR_CMP_SHIFT) &
+					p10_EVENT_THR_CMP_MASK;
+				mmcra |= thresh_cmp_val(val);
 			}
 		}