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 <eajames@linux.ibm.com>
Link: https://lore.kernel.org/r/20211019205307.36946-3-eajames@linux.ibm.comSigned-off-by: Joel Stanley <joel@jms.id.au>

drivers/fsi/fsi-occ.c

@@ -46,6 +46,9 @@ struct occ {
 	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;
@@ -208,6 +211,22 @@ static const struct file_operations occ_fops = {
 	.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)
 {
@@ -236,7 +255,7 @@ static int occ_verify_checksum(struct occ *occ, struct occ_response *resp,
 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];
@@ -271,16 +290,17 @@ static int occ_getsram(struct occ *occ, u32 offset, void *data, ssize_t len)
 		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);
@@ -296,7 +316,7 @@ static int occ_putsram(struct occ *occ, const void *data, ssize_t 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;
@@ -343,18 +363,19 @@ static int occ_putsram(struct occ *occ, const void *data, ssize_t len,
 		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]);
@@ -372,7 +393,7 @@ static int occ_putsram(struct occ *occ, const void *data, ssize_t len,
 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;
 
@@ -403,18 +424,19 @@ static int occ_trigger_attn(struct occ *occ)
 		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]);
@@ -437,6 +459,7 @@ int fsi_occ_submit(struct device *dev, const void *request, size_t req_len,
 		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;
@@ -445,11 +468,13 @@ int fsi_occ_submit(struct device *dev, const void *request, size_t req_len,
 	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;
 	}
 
@@ -459,6 +484,10 @@ int fsi_occ_submit(struct device *dev, const void *request, size_t req_len,
 
 	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
 	 * number of 0 which would pass the response check below even if the
@@ -509,7 +538,7 @@ int fsi_occ_submit(struct device *dev, const void *request, size_t req_len,
 	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;
 	}
@@ -525,10 +554,11 @@ int fsi_occ_submit(struct device *dev, const void *request, size_t req_len,
 			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;