selftests/pcie_bwctrl: Create selftests

Create selftests for PCIe BW control through the PCIe cooling device sysfs
interface.

First, the BW control selftest finds the PCIe Port to test with. By
default, the PCIe Port with the highest Link Speed is selected but
another PCIe Port can be provided with -d parameter.

The actual test steps the cur_state of the cooling device one-by-one
from max_state to what the cur_state was initially. The speed change
is confirmed by observing the current_link_speed for the corresponding
PCIe Port.

Link: https://lore.kernel.org/r/20241018144755.7875-10-ilpo.jarvinen@linux.intel.com
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

MAINTAINERS

@@ -17940,6 +17940,7 @@ S:	Supported
 F:	drivers/pci/pcie/bwctrl.c
 F:	drivers/thermal/pcie_cooling.c
 F:	include/linux/pci-bwctrl.h
+F:	tools/testing/selftests/pcie_bwctrl/
 
 PCIE DRIVER FOR AMAZON ANNAPURNA LABS
 M:	Jonathan Chocron <jonnyc@amazon.com>

tools/testing/selftests/Makefile

@@ -72,6 +72,7 @@ TARGETS += net/packetdrill
 TARGETS += net/rds
 TARGETS += net/tcp_ao
 TARGETS += nsfs
+TARGETS += pcie_bwctrl
 TARGETS += perf_events
 TARGETS += pidfd
 TARGETS += pid_namespace

tools/testing/selftests/pcie_bwctrl/Makefile

@@ -0,0 +1,2 @@
+TEST_PROGS = set_pcie_cooling_state.sh
+include ../lib.mk

tools/testing/selftests/pcie_bwctrl/set_pcie_cooling_state.sh

@@ -0,0 +1,122 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+SYSFS=
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+retval=0
+skipmsg="skip all tests:"
+
+PCIEPORTTYPE="PCIe_Port_Link_Speed"
+
+prerequisite()
+{
+	local ports
+
+	if [ $UID != 0 ]; then
+		echo $skipmsg must be run as root >&2
+		exit $ksft_skip
+	fi
+
+	SYSFS=`mount -t sysfs | head -1 | awk '{ print $3 }'`
+
+	if [ ! -d "$SYSFS" ]; then
+		echo $skipmsg sysfs is not mounted >&2
+		exit $ksft_skip
+	fi
+
+	if ! ls $SYSFS/class/thermal/cooling_device* > /dev/null 2>&1; then
+		echo $skipmsg thermal cooling devices missing >&2
+		exit $ksft_skip
+	fi
+
+	ports=`grep -e "^$PCIEPORTTYPE" $SYSFS/class/thermal/cooling_device*/type | wc -l`
+	if [ $ports -eq 0 ]; then
+		echo $skipmsg pcie cooling devices missing >&2
+		exit $ksft_skip
+	fi
+}
+
+testport=
+find_pcie_port()
+{
+	local patt="$1"
+	local pcieports
+	local max
+	local cur
+	local delta
+	local bestdelta=-1
+
+	pcieports=`grep -l -F -e "$patt" /sys/class/thermal/cooling_device*/type`
+	if [ -z "$pcieports" ]; then
+		return
+	fi
+	pcieports=${pcieports//\/type/}
+	# Find the port with the highest PCIe Link Speed
+	for port in $pcieports; do
+		max=`cat $port/max_state`
+		cur=`cat $port/cur_state`
+		delta=$((max-cur))
+		if [ $delta -gt $bestdelta ]; then
+			testport="$port"
+			bestdelta=$delta
+		fi
+	done
+}
+
+sysfspcidev=
+find_sysfs_pci_dev()
+{
+	local typefile="$1/type"
+	local pcidir
+
+	pcidir="$SYSFS/bus/pci/devices/`sed -e "s|^${PCIEPORTTYPE}_||g" $typefile`"
+
+	if [ -r "$pcidir/current_link_speed" ]; then
+		sysfspcidev="$pcidir/current_link_speed"
+	fi
+}
+
+usage()
+{
+	echo "Usage $0 [ -d dev ]"
+	echo -e "\t-d: PCIe port BDF string (e.g., 0000:00:04.0)"
+}
+
+pattern="$PCIEPORTTYPE"
+parse_arguments()
+{
+	while getopts d:h opt; do
+		case $opt in
+			h)
+				usage "$0"
+				exit 0
+				;;
+			d)
+				pattern="$PCIEPORTTYPE_$OPTARG"
+				;;
+			*)
+				usage "$0"
+				exit 0
+				;;
+		esac
+	done
+}
+
+parse_arguments "$@"
+prerequisite
+find_pcie_port "$pattern"
+if [ -z "$testport" ]; then
+	echo $skipmsg "pcie cooling device not found from sysfs" >&2
+	exit $ksft_skip
+fi
+find_sysfs_pci_dev "$testport"
+if [ -z "$sysfspcidev" ]; then
+	echo $skipmsg "PCIe port device not found from sysfs" >&2
+	exit $ksft_skip
+fi
+
+./set_pcie_speed.sh "$testport" "$sysfspcidev"
+retval=$?
+
+exit $retval

tools/testing/selftests/pcie_bwctrl/set_pcie_speed.sh

@@ -0,0 +1,67 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+set -e
+
+TESTNAME=set_pcie_speed
+
+declare -a PCIELINKSPEED=(
+	"2.5 GT/s PCIe"
+	"5.0 GT/s PCIe"
+	"8.0 GT/s PCIe"
+	"16.0 GT/s PCIe"
+	"32.0 GT/s PCIe"
+	"64.0 GT/s PCIe"
+)
+
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+retval=0
+
+coolingdev="$1"
+statefile="$coolingdev/cur_state"
+maxfile="$coolingdev/max_state"
+linkspeedfile="$2"
+
+oldstate=`cat $statefile`
+maxstate=`cat $maxfile`
+
+set_state()
+{
+	local state=$1
+	local linkspeed
+	local expected_linkspeed
+
+	echo $state > $statefile
+
+	sleep 1
+
+	linkspeed="`cat $linkspeedfile`"
+	expected_linkspeed=$((maxstate-state))
+	expected_str="${PCIELINKSPEED[$expected_linkspeed]}"
+	if [ ! "${expected_str}" = "${linkspeed}" ]; then
+		echo "$TESTNAME failed: expected: ${expected_str}; got ${linkspeed}"
+		retval=1
+	fi
+}
+
+cleanup_skip ()
+{
+	set_state $oldstate
+	exit $ksft_skip
+}
+
+trap cleanup_skip EXIT
+
+echo "$TESTNAME: testing states $maxstate .. $oldstate with $coolingdev"
+for i in $(seq $maxstate -1 $oldstate); do
+	set_state "$i"
+done
+
+trap EXIT
+if [ $retval -eq 0 ]; then
+	echo "$TESTNAME [PASS]"
+else
+	echo "$TESTNAME [FAIL]"
+fi
+exit $retval