wilc1000: handled extra bytes received before response header in SPI

In SPI communication, found that extra bytes were received before the
start of response header especially at lower clock speed. Added logic to
ignore extra bytes till the start of response header.

Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>

Author: ajaykathat

drivers/staging/wilc1000/spi.c

@@ -91,16 +91,15 @@ struct wilc_spi_cmd {
 } __packed;
 
 struct wilc_spi_read_rsp_data {
-	u8 rsp_cmd_type;
-	u8 status;
-	u8 resp_header;
-	u8 resp_data[4];
+	u8 header;
+	u8 data[4];
 	u8 crc[];
 } __packed;
 
 struct wilc_spi_rsp_data {
 	u8 rsp_cmd_type;
 	u8 status;
+	u8 data[];
 } __packed;
 
 struct wilc_spi_special_cmd_rsp {
@@ -480,6 +479,7 @@ static int spi_data_write(struct wilc *wilc, u8 *b, u32 sz)
  *      Spi Internal Read/Write Function
  *
  ********************************************/
+#define WILC_SPI_RSP_HDR_EXTRA_DATA (3)
 static int wilc_spi_single_read(struct wilc *wilc, u8 cmd, u32 adr, void *b,
 				u8 clockless)
 {
@@ -489,7 +489,9 @@ static int wilc_spi_single_read(struct wilc *wilc, u8 cmd, u32 adr, void *b,
 	int cmd_len, resp_len = 0;
 	u8 crc[2];
 	struct wilc_spi_cmd *c;
-	struct wilc_spi_read_rsp_data *r;
+	struct wilc_spi_rsp_data *rsp;
+	struct wilc_spi_read_rsp_data *r_data;
+	int i = 0;
 
 	memset(wb, 0x0, sizeof(wb));
 	memset(rb, 0x0, sizeof(rb));
@@ -511,7 +513,7 @@ static int wilc_spi_single_read(struct wilc *wilc, u8 cmd, u32 adr, void *b,
 	}
 
 	cmd_len = offsetof(struct wilc_spi_cmd, u.simple_cmd.crc);
-	resp_len = sizeof(*r);
+	resp_len = sizeof(*rsp) + sizeof(*r_data) + WILC_SPI_RSP_HDR_EXTRA_DATA;
 
 	if (!spi_priv->crc_off) {
 		c->u.simple_cmd.crc[0] = wilc_get_crc7(wb, cmd_len);
@@ -530,34 +532,42 @@ static int wilc_spi_single_read(struct wilc *wilc, u8 cmd, u32 adr, void *b,
 		return -EINVAL;
 	}
 
-	r = (struct wilc_spi_read_rsp_data *)&rb[cmd_len];
+	rsp = (struct wilc_spi_rsp_data *)&rb[cmd_len];
 	/*
 	 * Clockless registers operations might return unexptected responses,
 	 * even if successful.
 	 */
-	if (r->rsp_cmd_type != cmd && !clockless) {
+	if (rsp->rsp_cmd_type != cmd && !clockless) {
 		dev_err(&spi->dev,
 			"Failed cmd response, cmd (%02x), resp (%02x)\n",
-			cmd, r->rsp_cmd_type);
+			cmd, rsp->rsp_cmd_type);
 		return -EINVAL;
 	}
 
-	if (r->status != WILC_SPI_COMMAND_STAT_SUCCESS && !clockless) {
+	if (rsp->status != WILC_SPI_COMMAND_STAT_SUCCESS && !clockless) {
 		dev_err(&spi->dev, "Failed cmd state response state (%02x)\n",
-			r->status);
+			rsp->status);
 		return -EINVAL;
 	}
 
-	if (WILC_GET_RESP_HDR_START(r->resp_header) != 0xf) {
-		dev_err(&spi->dev, "Error, data read response (%02x)\n",
-			r->resp_header);
+	do {
+		if (WILC_GET_RESP_HDR_START(rsp->data[i]) == 0xf)
+			break;
+		i++;
+	} while (i < SPI_RESP_RETRY_COUNT);
+
+	if (i >= SPI_RESP_RETRY_COUNT) {
+		dev_err(&spi->dev, "Error, data read response\n");
 		return -EINVAL;
 	}
+
+	r_data = (struct wilc_spi_read_rsp_data *)&rsp->data[i];
+
 	if (b)
-		memcpy(b, r->resp_data, 4);
+		memcpy(b, r_data->data, 4);
 
 	if (!spi_priv->crc_off)
-		memcpy(crc, r->crc, 2);
+		memcpy(crc, r_data->crc, 2);
 
 	return 0;
 }