On Wed, Jun 16, 2021 at 07:12:40PM +0530, Pratik R. Sampat wrote:

Adds a generic interface to represent the energy and frequency related
PAPR attributes on the system using the new H_CALL
"H_GET_ENERGY_SCALE_INFO".

H_GET_EM_PARMS H_CALL was previously responsible for exporting this
information in the lparcfg, however the H_GET_EM_PARMS H_CALL
will be deprecated P10 onwards.

The H_GET_ENERGY_SCALE_INFO H_CALL is of the following call format:
hcall(
  uint64 H_GET_ENERGY_SCALE_INFO,  // Get energy scale info
  uint64 flags,           // Per the flag request
  uint64 firstAttributeId,// The attribute id
  uint64 bufferAddress,   // Guest physical address of the output buffer
  uint64 bufferSize       // The size in bytes of the output buffer
);

This H_CALL can query either all the attributes at once with
firstAttributeId = 0, flags = 0 as well as query only one attribute
at a time with firstAttributeId = id

For a single attribute, the “firstAttributeId” must be set by the
caller to the attribute id to retrieve and the “singleAttribute” field
in “flags” must also be set to a 1.

If we don't set the "flags" to 1, while specifying a firstAttributeId,
the hypervisor will populate the buffer with the details pertaining to
all the attributes beginning with firstAttributeId.

The output buffer consists of the following
1. number of attributes              - 8 bytes
2. array offset to the data location - 8 bytes
3. version info                      - 1 byte
4. A data array of size num attributes, which contains the following:
  a. attribute ID              - 8 bytes
  b. attribute value in number - 8 bytes
  c. attribute name in string  - 64 bytes
  d. attribute value in string - 64 bytes

[..snip..]

+
+static ssize_t papr_show_value(struct kobject *kobj,
+				struct kobj_attribute *attr,
+				char *buf)
+{
+	struct papr_attr *pattr = container_of(attr, struct papr_attr, attr);
+	struct hv_energy_scale_buffer *t_buf;
+	struct energy_scale_attributes *t_ea;
+	int data_offset, ret = 0;
+
+	t_buf = kmalloc(sizeof(*t_buf), GFP_KERNEL);
+	if (t_buf == NULL)
+		return -ENOMEM;
+
+	ret = plpar_hcall_norets(H_GET_ENERGY_SCALE_INFO, 0,
+				 pattr->id, virt_to_phys(t_buf),
+				 sizeof(*t_buf));
+

In this case, since we are interested in only one attribute, we can
make the call

	ret = plpar_hcall_norets(H_GET_ENERGY_SCALE_INFO, 1,
				 pattr->id, virt_to_phys(t_buf),
				 sizeof(*t_buf));

setting flags=1.

Same in the function papr_show_value_desc() below

--
Thanks and Regards
gautham.

+	if (ret != H_SUCCESS) {
+		pr_warn("hcall failed: H_GET_ENERGY_SCALE_INFO");
+		goto out;
+	}
+
+	data_offset = be64_to_cpu(t_buf->array_offset) -
+			(sizeof(t_buf->num_attr) +
+			sizeof(t_buf->array_offset) +
+			sizeof(t_buf->data_header_version));
+
+	t_ea = (struct energy_scale_attributes *) &t_buf->data[data_offset];
+
+	ret = sprintf(buf, "%llu\n", be64_to_cpu(t_ea->attr_value));
+	if (ret < 0)
+		ret = -EIO;
+out:
+	kfree(t_buf);
+
+	return ret;
+}
+
+static ssize_t papr_show_value_desc(struct kobject *kobj,
+				     struct kobj_attribute *attr,
+				     char *buf)
+{
+	struct papr_attr *pattr = container_of(attr, struct papr_attr, attr);
+	struct hv_energy_scale_buffer *t_buf;
+	struct energy_scale_attributes *t_ea;
+	int data_offset, ret = 0;
+
+	t_buf = kmalloc(sizeof(*t_buf), GFP_KERNEL);
+	if (t_buf == NULL)
+		return -ENOMEM;
+
+	ret = plpar_hcall_norets(H_GET_ENERGY_SCALE_INFO, 0,
+				 pattr->id, virt_to_phys(t_buf),
+				 sizeof(*t_buf));
+
+	if (ret != H_SUCCESS) {
+		pr_warn("hcall failed: H_GET_ENERGY_SCALE_INFO");
+		goto out;
+	}
+
+	data_offset = be64_to_cpu(t_buf->array_offset) -
+			(sizeof(t_buf->num_attr) +
+			sizeof(t_buf->array_offset) +
+			sizeof(t_buf->data_header_version));
+
+	t_ea = (struct energy_scale_attributes *) &t_buf->data[data_offset];
+
+	ret = sprintf(buf, "%s\n", t_ea->attr_value_desc);
+	if (ret < 0)
+		ret = -EIO;
+out:
+	kfree(t_buf);
+
+	return ret;
+}
+
+static struct papr_ops_info {
+	const char *attr_name;
+	ssize_t (*show)(struct kobject *kobj, struct kobj_attribute *attr,
+			char *buf);
+} ops_info[] = {
+	{ "desc", papr_show_desc },
+	{ "value", papr_show_value },
+	{ "value_desc", papr_show_value_desc },
+};
+
+static void add_attr(u64 id, int index, struct papr_attr *attr)
+{
+	attr->id = id;
+	sysfs_attr_init(&attr->attr.attr);
+	attr->attr.attr.name = ops_info[index].attr_name;
+	attr->attr.attr.mode = 0444;
+	attr->attr.show = ops_info[index].show;
+}
+
+static int add_attr_group(u64 id, int len, struct papr_group *pg,
+			  bool show_val_desc)
+{
+	int i;
+
+	for (i = 0; i < len; i++) {
+		if (!strcmp(ops_info[i].attr_name, "value_desc") &&
+		    !show_val_desc) {
+			continue;
+		}
+		add_attr(id, i, &pg->pgattrs[i]);
+		pg->pg.attrs[i] = &pg->pgattrs[i].attr.attr;
+	}
+
+	return sysfs_create_group(escale_kobj, &pg->pg);
+}
+
+
+static int __init papr_init(void)
+{
+	uint64_t num_attr;
+	int ret, idx, i, data_offset;
+
+	em_buf = kmalloc(sizeof(*em_buf), GFP_KERNEL);
+	if (em_buf == NULL)
+		return -ENOMEM;
+	/*
+	 * hcall(
+	 * uint64 H_GET_ENERGY_SCALE_INFO,  // Get energy scale info
+	 * uint64 flags,            // Per the flag request
+	 * uint64 firstAttributeId, // The attribute id
+	 * uint64 bufferAddress,    // Guest physical address of the output buffer
+	 * uint64 bufferSize);      // The size in bytes of the output buffer
+	 */
+	ret = plpar_hcall_norets(H_GET_ENERGY_SCALE_INFO, 0, 0,
+				 virt_to_phys(em_buf), sizeof(*em_buf));
+
+	if (!firmware_has_feature(FW_FEATURE_LPAR) || ret != H_SUCCESS ||
+	    em_buf->data_header_version != 0x1) {
+		pr_warn("hcall failed: H_GET_ENERGY_SCALE_INFO");
+		goto out;
+	}
+
+	num_attr = be64_to_cpu(em_buf->num_attr);
+
+	/*
+	 * Typecast the energy buffer to the attribute structure at the offset
+	 * specified in the buffer
+	 */
+	data_offset = be64_to_cpu(em_buf->array_offset) -
+			(sizeof(em_buf->num_attr) +
+			sizeof(em_buf->array_offset) +
+			sizeof(em_buf->data_header_version));
+
+	ea = (struct energy_scale_attributes *) &em_buf->data[data_offset];
+
+	pgs = kcalloc(num_attr, sizeof(*pgs), GFP_KERNEL);
+	if (!pgs)
+		goto out_pgs;
+
+	papr_kobj = kobject_create_and_add("papr", firmware_kobj);
+	if (!papr_kobj) {
+		pr_warn("kobject_create_and_add papr failed\n");
+		goto out_kobj;
+	}
+
+	escale_kobj = kobject_create_and_add("energy_scale_info", papr_kobj);
+	if (!escale_kobj) {
+		pr_warn("kobject_create_and_add energy_scale_info failed\n");
+		goto out_ekobj;
+	}
+
+	for (idx = 0; idx < num_attr; idx++) {
+		char buf[4];
+		bool show_val_desc = true;
+
+		pgs[idx].pgattrs = kcalloc(MAX_ATTRS,
+					   sizeof(*pgs[idx].pgattrs),
+					   GFP_KERNEL);
+		if (!pgs[idx].pgattrs)
+			goto out_kobj;
+
+		pgs[idx].pg.attrs = kcalloc(MAX_ATTRS + 1,
+					    sizeof(*pgs[idx].pg.attrs),
+					    GFP_KERNEL);
+		if (!pgs[idx].pg.attrs) {
+			kfree(pgs[idx].pgattrs);
+			goto out_kobj;
+		}
+
+		sprintf(buf, "%lld", be64_to_cpu(ea[idx].attr_id));
+		pgs[idx].pg.name = buf;
+
+		/* Do not add the value description if it does not exist */
+		if (strlen(ea[idx].attr_value_desc) == 0)
+			show_val_desc = false;
+
+		if (add_attr_group(be64_to_cpu(ea[idx].attr_id),
+				   MAX_ATTRS, &pgs[idx], show_val_desc)) {
+			pr_warn("Failed to create papr attribute group %s\n",
+				pgs[idx].pg.name);
+			goto out_pgattrs;
+		}
+	}
+
+	return 0;
+
+out_pgattrs:
+	for (i = 0; i < MAX_ATTRS; i++) {
+		kfree(pgs[i].pgattrs);
+		kfree(pgs[i].pg.attrs);
+	}
+out_ekobj:
+	kobject_put(escale_kobj);
+out_kobj:
+	kobject_put(papr_kobj);
+out_pgs:
+	kfree(pgs);
+out:
+	kfree(em_buf);
+
+	return -ENOMEM;
+}
+
+machine_device_initcall(pseries, papr_init);
-- 
2.30.2