wl1271: Handle large SPI transfers

The HW supports up to 4095 bytes transfers via SPI. The SPI read & write
operations do not handle larger transfers, causing the HW to stall in such
cases.

Fix this by fragmenting large transfers into smaller chunks, and
transferring each one separately.
Signed-off-by: Ido Yariv <ido@wizery.com>
Tested-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>

drivers/net/wireless/wl12xx/wl1271_spi.c

@@ -63,6 +63,11 @@
 		((WL1271_BUSY_WORD_LEN - 4) / sizeof(u32))
 #define HW_ACCESS_WSPI_INIT_CMD_MASK  0
 
+/* HW limitation: maximum possible chunk size is 4095 bytes */
+#define WSPI_MAX_CHUNK_SIZE    4092
+
+#define WSPI_MAX_NUM_OF_CHUNKS (WL1271_AGGR_BUFFER_SIZE / WSPI_MAX_CHUNK_SIZE)
+
 static inline struct spi_device *wl_to_spi(struct wl1271 *wl)
 {
 	return wl->if_priv;
@@ -202,17 +207,22 @@ static int wl1271_spi_read_busy(struct wl1271 *wl)
 static void wl1271_spi_raw_read(struct wl1271 *wl, int addr, void *buf,
 				size_t len, bool fixed)
 {
-	struct spi_transfer t[3];
+	struct spi_transfer t[2];
 	struct spi_message m;
 	u32 *busy_buf;
 	u32 *cmd;
+	u32 chunk_len;
+
+	while (len > 0) {
+		chunk_len = min((size_t)WSPI_MAX_CHUNK_SIZE, len);
 
 		cmd = &wl->buffer_cmd;
 		busy_buf = wl->buffer_busyword;
 
 		*cmd = 0;
 		*cmd |= WSPI_CMD_READ;
-	*cmd |= (len << WSPI_CMD_BYTE_LENGTH_OFFSET) & WSPI_CMD_BYTE_LENGTH;
+		*cmd |= (chunk_len << WSPI_CMD_BYTE_LENGTH_OFFSET) &
+			WSPI_CMD_BYTE_LENGTH;
 		*cmd |= addr & WSPI_CMD_BYTE_ADDR;
 
 		if (fixed)
@@ -236,7 +246,7 @@ static void wl1271_spi_raw_read(struct wl1271 *wl, int addr, void *buf,
 
 		if (!(busy_buf[WL1271_BUSY_WORD_CNT - 1] & 0x1) &&
 		    wl1271_spi_read_busy(wl)) {
-		memset(buf, 0, len);
+			memset(buf, 0, chunk_len);
 			return;
 		}
 
@@ -244,48 +254,70 @@ static void wl1271_spi_raw_read(struct wl1271 *wl, int addr, void *buf,
 		memset(t, 0, sizeof(t));
 
 		t[0].rx_buf = buf;
-	t[0].len = len;
+		t[0].len = chunk_len;
 		t[0].cs_change = true;
 		spi_message_add_tail(&t[0], &m);
 
 		spi_sync(wl_to_spi(wl), &m);
 
 		wl1271_dump(DEBUG_SPI, "spi_read cmd -> ", cmd, sizeof(*cmd));
-	wl1271_dump(DEBUG_SPI, "spi_read buf <- ", buf, len);
+		wl1271_dump(DEBUG_SPI, "spi_read buf <- ", buf, chunk_len);
+
+		if (!fixed)
+			addr += chunk_len;
+		buf += chunk_len;
+		len -= chunk_len;
+	}
 }
 
 static void wl1271_spi_raw_write(struct wl1271 *wl, int addr, void *buf,
 			  size_t len, bool fixed)
 {
-	struct spi_transfer t[2];
+	struct spi_transfer t[2 * WSPI_MAX_NUM_OF_CHUNKS];
 	struct spi_message m;
+	u32 commands[WSPI_MAX_NUM_OF_CHUNKS];
 	u32 *cmd;
+	u32 chunk_len;
+	int i;
 
-	cmd = &wl->buffer_cmd;
+	WARN_ON(len > WL1271_AGGR_BUFFER_SIZE);
+
+	spi_message_init(&m);
+	memset(t, 0, sizeof(t));
+
+	cmd = &commands[0];
+	i = 0;
+	while (len > 0) {
+		chunk_len = min((size_t)WSPI_MAX_CHUNK_SIZE, len);
 
 		*cmd = 0;
 		*cmd |= WSPI_CMD_WRITE;
-	*cmd |= (len << WSPI_CMD_BYTE_LENGTH_OFFSET) & WSPI_CMD_BYTE_LENGTH;
+		*cmd |= (chunk_len << WSPI_CMD_BYTE_LENGTH_OFFSET) &
+			WSPI_CMD_BYTE_LENGTH;
 		*cmd |= addr & WSPI_CMD_BYTE_ADDR;
 
 		if (fixed)
 			*cmd |= WSPI_CMD_FIXED;
 
-	spi_message_init(&m);
-	memset(t, 0, sizeof(t));
+		t[i].tx_buf = cmd;
+		t[i].len = sizeof(*cmd);
+		spi_message_add_tail(&t[i++], &m);
 
-	t[0].tx_buf = cmd;
-	t[0].len = sizeof(*cmd);
-	spi_message_add_tail(&t[0], &m);
+		t[i].tx_buf = buf;
+		t[i].len = chunk_len;
+		spi_message_add_tail(&t[i++], &m);
 
-	t[1].tx_buf = buf;
-	t[1].len = len;
-	spi_message_add_tail(&t[1], &m);
+		wl1271_dump(DEBUG_SPI, "spi_write cmd -> ", cmd, sizeof(*cmd));
+		wl1271_dump(DEBUG_SPI, "spi_write buf -> ", buf, chunk_len);
 
-	spi_sync(wl_to_spi(wl), &m);
+		if (!fixed)
+			addr += chunk_len;
+		buf += chunk_len;
+		len -= chunk_len;
+		cmd++;
+	}
 
-	wl1271_dump(DEBUG_SPI, "spi_write cmd -> ", cmd, sizeof(*cmd));
-	wl1271_dump(DEBUG_SPI, "spi_write buf -> ", buf, len);
+	spi_sync(wl_to_spi(wl), &m);
 }
 
 static irqreturn_t wl1271_irq(int irq, void *cookie)