s390/cio: export CHPID operating speed

JIRA: https://issues.redhat.com/browse/RHEL-50790

commit 0f987e6
Author: Peter Oberparleiter <oberpar@linux.ibm.com>
Date:   Tue Mar 26 17:03:24 2024 +0100

    s390/cio: export CHPID operating speed

    Add a per-CHPID sysfs attribute named "speed_bps" that provides the
    operating speed of the associated channel path in bits per second,
    or 0 if the operating speed is not available.

    Example:

    $ cat /sys/devices/css0/chp0.32/speed_bps
    32G

    Reviewed-by: Vineeth Vijayan <vneethv@linux.ibm.com>
    Acked-by: Heiko Carstens <hca@linux.ibm.com>
    Signed-off-by: Peter Oberparleiter <oberpar@linux.ibm.com>
    Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

Signed-off-by: Mete Durlu <mdurlu@redhat.com>

Author: Mete Durlu

drivers/s390/cio/chp.c

@@ -392,6 +392,35 @@ static ssize_t chp_esc_show(struct device *dev,
 }
 static DEVICE_ATTR(esc, 0444, chp_esc_show, NULL);
 
+static char apply_max_suffix(unsigned long *value, unsigned long base)
+{
+	static char suffixes[] = { 0, 'K', 'M', 'G', 'T' };
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(suffixes) - 1; i++) {
+		if (*value < base || *value % base != 0)
+			break;
+		*value /= base;
+	}
+
+	return suffixes[i];
+}
+
+static ssize_t speed_bps_show(struct device *dev,
+			      struct device_attribute *attr, char *buf)
+{
+	struct channel_path *chp = to_channelpath(dev);
+	unsigned long speed = chp->speed;
+	char suffix;
+
+	suffix = apply_max_suffix(&speed, 1000);
+
+	return suffix ? sysfs_emit(buf, "%lu%c\n", speed, suffix) :
+			sysfs_emit(buf, "%lu\n", speed);
+}
+
+static DEVICE_ATTR_RO(speed_bps);
+
 static ssize_t util_string_read(struct file *filp, struct kobject *kobj,
 				struct bin_attribute *attr, char *buf,
 				loff_t off, size_t count)
@@ -423,6 +452,7 @@ static struct attribute *chp_attrs[] = {
 	&dev_attr_chid.attr,
 	&dev_attr_chid_external.attr,
 	&dev_attr_esc.attr,
+	&dev_attr_speed_bps.attr,
 	NULL,
 };
 static struct attribute_group chp_attr_group = {

drivers/s390/cio/chp.h

@@ -52,6 +52,7 @@ struct channel_path {
 	int cmg;
 	int shared;
 	int extended;
+	unsigned long speed;
 	struct cmg_chars cmg_chars;
 };
 

drivers/s390/cio/chsc.c

@@ -1052,6 +1052,18 @@ chsc_initialize_cmg_chars(struct channel_path *chp, u8 cmcv,
 	}
 }
 
+static unsigned long scmc_get_speed(u32 s, u32 p)
+{
+	unsigned long speed = s;
+
+	if (!p)
+		p = 8;
+	while (p--)
+		speed *= 10;
+
+	return speed;
+}
+
 int chsc_get_channel_measurement_chars(struct channel_path *chp)
 {
 	unsigned long flags;
@@ -1072,16 +1084,19 @@ int chsc_get_channel_measurement_chars(struct channel_path *chp)
 		u32 : 21;
 		u32 chpid : 8;
 		u32 cmcv : 5;
-		u32 : 11;
+		u32 : 7;
+		u32 cmgp : 4;
 		u32 cmgq : 8;
 		u32 cmg : 8;
-		u32 zeroes3;
+		u32 : 16;
+		u32 cmgs : 16;
 		u32 data[NR_MEASUREMENT_CHARS];
 	} *scmc_area;
 
 	chp->shared = -1;
 	chp->cmg = -1;
 	chp->extended = 0;
+	chp->speed = 0;
 
 	if (!css_chsc_characteristics.scmc || !css_chsc_characteristics.secm)
 		return -EINVAL;
@@ -1112,6 +1127,7 @@ int chsc_get_channel_measurement_chars(struct channel_path *chp)
 	chp->cmg = scmc_area->cmg;
 	chp->shared = scmc_area->shared;
 	chp->extended = scmc_area->extended;
+	chp->speed = scmc_get_speed(scmc_area->cmgs, scmc_area->cmgp);
 	chsc_initialize_cmg_chars(chp, scmc_area->cmcv,
 				  (struct cmg_chars *) &scmc_area->data);
 out: