powerpc/nvdimm: Add support for multibyte read/write for metadata

SCM_READ/WRITE_MEATADATA hcall supports multibyte read/write. This patch
updates the metadata read/write to use 1, 2, 4 or 8 byte read/write as
mentioned in PAPR document.

READ/WRITE_METADATA hcall supports the 1, 2, 4, or 8 bytes read/write.
For other values hcall results H_P3.

Hypervisor stores the metadata contents in big-endian format and in-order
to enable read/write in different granularity, we need to switch the contents
to big-endian before calling HCALL.

Based on an patch from Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/platforms/pseries/papr_scm.c

@@ -100,39 +100,99 @@ static int papr_scm_meta_get(struct papr_scm_priv *p,
 			     struct nd_cmd_get_config_data_hdr *hdr)
 {
 	unsigned long data[PLPAR_HCALL_BUFSIZE];
+	unsigned long offset, data_offset;
+	int len, read;
 	int64_t ret;
 
-	if (hdr->in_offset >= p->metadata_size || hdr->in_length != 1)
+	if ((hdr->in_offset + hdr->in_length) >= p->metadata_size)
 		return -EINVAL;
 
+	for (len = hdr->in_length; len; len -= read) {
+
+		data_offset = hdr->in_length - len;
+		offset = hdr->in_offset + data_offset;
+
+		if (len >= 8)
+			read = 8;
+		else if (len >= 4)
+			read = 4;
+		else if (len >= 2)
+			read = 2;
+		else
+			read = 1;
+
 		ret = plpar_hcall(H_SCM_READ_METADATA, data, p->drc_index,
-			hdr->in_offset, 1);
+				  offset, read);
 
 		if (ret == H_PARAMETER) /* bad DRC index */
 			return -ENODEV;
 		if (ret)
 			return -EINVAL; /* other invalid parameter */
 
-	hdr->out_buf[0] = data[0] & 0xff;
+		switch (read) {
+		case 8:
+			*(uint64_t *)(hdr->out_buf + data_offset) = be64_to_cpu(data[0]);
+			break;
+		case 4:
+			*(uint32_t *)(hdr->out_buf + data_offset) = be32_to_cpu(data[0] & 0xffffffff);
+			break;
 
+		case 2:
+			*(uint16_t *)(hdr->out_buf + data_offset) = be16_to_cpu(data[0] & 0xffff);
+			break;
+
+		case 1:
+			*(uint8_t *)(hdr->out_buf + data_offset) = (data[0] & 0xff);
+			break;
+		}
+	}
 	return 0;
 }
 
 static int papr_scm_meta_set(struct papr_scm_priv *p,
 			     struct nd_cmd_set_config_hdr *hdr)
 {
+	unsigned long offset, data_offset;
+	int len, wrote;
+	unsigned long data;
+	__be64 data_be;
 	int64_t ret;
 
-	if (hdr->in_offset >= p->metadata_size || hdr->in_length != 1)
+	if ((hdr->in_offset + hdr->in_length) >= p->metadata_size)
 		return -EINVAL;
 
-	ret = plpar_hcall_norets(H_SCM_WRITE_METADATA,
-			p->drc_index, hdr->in_offset, hdr->in_buf[0], 1);
+	for (len = hdr->in_length; len; len -= wrote) {
+
+		data_offset = hdr->in_length - len;
+		offset = hdr->in_offset + data_offset;
+
+		if (len >= 8) {
+			data = *(uint64_t *)(hdr->in_buf + data_offset);
+			data_be = cpu_to_be64(data);
+			wrote = 8;
+		} else if (len >= 4) {
+			data = *(uint32_t *)(hdr->in_buf + data_offset);
+			data &= 0xffffffff;
+			data_be = cpu_to_be32(data);
+			wrote = 4;
+		} else if (len >= 2) {
+			data = *(uint16_t *)(hdr->in_buf + data_offset);
+			data &= 0xffff;
+			data_be = cpu_to_be16(data);
+			wrote = 2;
+		} else {
+			data_be = *(uint8_t *)(hdr->in_buf + data_offset);
+			data_be &= 0xff;
+			wrote = 1;
+		}
 
+		ret = plpar_hcall_norets(H_SCM_WRITE_METADATA, p->drc_index,
+					 offset, data_be, wrote);
 		if (ret == H_PARAMETER) /* bad DRC index */
 			return -ENODEV;
 		if (ret)
 			return -EINVAL; /* other invalid parameter */
+	}
 
 	return 0;
 }
@@ -154,7 +214,7 @@ int papr_scm_ndctl(struct nvdimm_bus_descriptor *nd_desc, struct nvdimm *nvdimm,
 		get_size_hdr = buf;
 
 		get_size_hdr->status = 0;
-		get_size_hdr->max_xfer = 1;
+		get_size_hdr->max_xfer = 8;
 		get_size_hdr->config_size = p->metadata_size;
 		*cmd_rc = 0;
 		break;