fsi: occ: Store the SBEFIFO FFDC in the user response buffer

If the SBEFIFO response indicates an error, store the response in the
user buffer and return an error. Previously, the user had no way of
obtaining the SBEFIFO FFDC.

The user's buffer now contains data in the event of a failure. No change
in the event of a successful transfer.

Signed-off-by: Eddie James <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Joel Stanley <[e-mail]>

drivers/fsi/fsi-occ.c

···
 	int idx;
 	u8 sequence_number;
 	void *buffer;
+	void *client_buffer;
+	size_t client_buffer_size;
+	size_t client_response_size;
 	enum versions version;
 	struct miscdevice mdev;
 	struct mutex occ_lock;
···
 	.release = occ_release,
 };
 
+static void occ_save_ffdc(struct occ *occ, __be32 *resp, size_t parsed_len,
+			  size_t resp_len)
+{
+	if (resp_len > parsed_len) {
+		size_t dh = resp_len - parsed_len;
+		size_t ffdc_len = (dh - 1) * 4; /* SBE words are four bytes */
+		__be32 *ffdc = &resp[parsed_len];
+
+		if (ffdc_len > occ->client_buffer_size)
+			ffdc_len = occ->client_buffer_size;
+
+		memcpy(occ->client_buffer, ffdc, ffdc_len);
+		occ->client_response_size = ffdc_len;
+	}
+}
+
 static int occ_verify_checksum(struct occ *occ, struct occ_response *resp,
 			       u16 data_length)
 {
···
 static int occ_getsram(struct occ *occ, u32 offset, void *data, ssize_t len)
 {
 	u32 data_len = ((len + 7) / 8) * 8;	/* must be multiples of 8 B */
-	size_t cmd_len, resp_data_len;
+	size_t cmd_len, parsed_len, resp_data_len;
 	size_t resp_len = OCC_MAX_RESP_WORDS;
 	__be32 *resp = occ->buffer;
 	__be32 cmd[6];
···
 		return rc;
 
 	rc = sbefifo_parse_status(occ->sbefifo, SBEFIFO_CMD_GET_OCC_SRAM,
-				  resp, resp_len, &resp_len);
+				  resp, resp_len, &parsed_len);
 	if (rc > 0) {
 		dev_err(occ->dev, "SRAM read returned failure status: %08x\n",
 			rc);
-		return -EBADMSG;
+		occ_save_ffdc(occ, resp, parsed_len, resp_len);
+		return -ECOMM;
 	} else if (rc) {
 		return rc;
 	}
 
-	resp_data_len = be32_to_cpu(resp[resp_len - 1]);
+	resp_data_len = be32_to_cpu(resp[parsed_len - 1]);
 	if (resp_data_len != data_len) {
 		dev_err(occ->dev, "SRAM read expected %d bytes got %zd\n",
 			data_len, resp_data_len);
···
 		       u8 seq_no, u16 checksum)
 {
 	u32 data_len = ((len + 7) / 8) * 8;	/* must be multiples of 8 B */
-	size_t cmd_len, resp_data_len;
+	size_t cmd_len, parsed_len, resp_data_len;
 	size_t resp_len = OCC_MAX_RESP_WORDS;
 	__be32 *buf = occ->buffer;
 	u8 *byte_buf;
···
 		return rc;
 
 	rc = sbefifo_parse_status(occ->sbefifo, SBEFIFO_CMD_PUT_OCC_SRAM,
-				  buf, resp_len, &resp_len);
+				  buf, resp_len, &parsed_len);
 	if (rc > 0) {
 		dev_err(occ->dev, "SRAM write returned failure status: %08x\n",
 			rc);
-		return -EBADMSG;
+		occ_save_ffdc(occ, buf, parsed_len, resp_len);
+		return -ECOMM;
 	} else if (rc) {
 		return rc;
 	}
 
-	if (resp_len != 1) {
+	if (parsed_len != 1) {
 		dev_err(occ->dev, "SRAM write response length invalid: %zd\n",
-			resp_len);
+			parsed_len);
 		rc = -EBADMSG;
 	} else {
 		resp_data_len = be32_to_cpu(buf[0]);
···
 static int occ_trigger_attn(struct occ *occ)
 {
 	__be32 *buf = occ->buffer;
-	size_t cmd_len, resp_data_len;
+	size_t cmd_len, parsed_len, resp_data_len;
 	size_t resp_len = OCC_MAX_RESP_WORDS;
 	int idx = 0, rc;
 
···
 		return rc;
 
 	rc = sbefifo_parse_status(occ->sbefifo, SBEFIFO_CMD_PUT_OCC_SRAM,
-				  buf, resp_len, &resp_len);
+				  buf, resp_len, &parsed_len);
 	if (rc > 0) {
 		dev_err(occ->dev, "SRAM attn returned failure status: %08x\n",
 			rc);
-		return -EBADMSG;
+		occ_save_ffdc(occ, buf, parsed_len, resp_len);
+		return -ECOMM;
 	} else if (rc) {
 		return rc;
 	}
 
-	if (resp_len != 1) {
+	if (parsed_len != 1) {
 		dev_err(occ->dev, "SRAM attn response length invalid: %zd\n",
-			resp_len);
+			parsed_len);
 		rc = -EBADMSG;
 	} else {
 		resp_data_len = be32_to_cpu(buf[0]);
···
 		msecs_to_jiffies(OCC_CMD_IN_PRG_WAIT_MS);
 	struct occ *occ = dev_get_drvdata(dev);
 	struct occ_response *resp = response;
+	size_t user_resp_len = *resp_len;
 	u8 seq_no;
 	u16 checksum = 0;
 	u16 resp_data_length;
···
 	int rc;
 	size_t i;
 
+	*resp_len = 0;
+
 	if (!occ)
 		return -ENODEV;
 
-	if (*resp_len < 7) {
-		dev_dbg(dev, "Bad resplen %zd\n", *resp_len);
+	if (user_resp_len < 7) {
+		dev_dbg(dev, "Bad resplen %zd\n", user_resp_len);
 		return -EINVAL;
 	}
 
···
 		checksum += byte_request[i];
 
 	mutex_lock(&occ->occ_lock);
+
+	occ->client_buffer = response;
+	occ->client_buffer_size = user_resp_len;
+	occ->client_response_size = 0;
 
 	/*
 	 * Get a sequence number and update the counter. Avoid a sequence
···
 	resp_data_length = get_unaligned_be16(&resp->data_length);
 
 	/* Message size is data length + 5 bytes header + 2 bytes checksum */
-	if ((resp_data_length + 7) > *resp_len) {
+	if ((resp_data_length + 7) > user_resp_len) {
 		rc = -EMSGSIZE;
 		goto done;
 	}
···
 			goto done;
 	}
 
-	*resp_len = resp_data_length + 7;
+	occ->client_response_size = resp_data_length + 7;
 	rc = occ_verify_checksum(occ, resp, resp_data_length);
 
  done:
+	*resp_len = occ->client_response_size;
 	mutex_unlock(&occ->occ_lock);
 
 	return rc;