libertas: document register meanings

Signed-off-by: Holger Schurig <hs4233@mail.mn-solutions.de>
Acked-by: Dan Williams <dcbw@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/libertas/if_cs.c

@@ -159,7 +159,9 @@ static int if_cs_poll_while_fw_download(struct if_cs_card *card, uint addr, u8 r
 
 
 
-/* First the bitmasks for the host/card interrupt/status registers: */
+/*
+ * First the bitmasks for the host/card interrupt/status registers:
+ */
 #define IF_CS_BIT_TX			0x0001
 #define IF_CS_BIT_RX			0x0002
 #define IF_CS_BIT_COMMAND		0x0004
@@ -167,35 +169,104 @@ static int if_cs_poll_while_fw_download(struct if_cs_card *card, uint addr, u8 r
 #define IF_CS_BIT_EVENT			0x0010
 #define	IF_CS_BIT_MASK			0x001f
 
-/* And now the individual registers and assorted masks */
+
+
+/*
+ * It's not really clear to me what the host status register is for. It
+ * needs to be set almost in union with "host int cause". The following
+ * bits from above are used:
+ *
+ *   IF_CS_BIT_TX         driver downloaded a data packet
+ *   IF_CS_BIT_RX         driver got a data packet
+ *   IF_CS_BIT_COMMAND    driver downloaded a command
+ *   IF_CS_BIT_RESP       not used (has some meaning with powerdown)
+ *   IF_CS_BIT_EVENT      driver read a host event
+ */
 #define IF_CS_HOST_STATUS		0x00000000
 
+/*
+ * With the host int cause register can the host (that is, Linux) cause
+ * an interrupt in the firmware, to tell the firmware about those events:
+ *
+ *   IF_CS_BIT_TX         a data packet has been downloaded
+ *   IF_CS_BIT_RX         a received data packet has retrieved
+ *   IF_CS_BIT_COMMAND    a firmware block or a command has been downloaded
+ *   IF_CS_BIT_RESP       not used (has some meaning with powerdown)
+ *   IF_CS_BIT_EVENT      a host event (link lost etc) has been retrieved
+ */
 #define IF_CS_HOST_INT_CAUSE		0x00000002
 
+/*
+ * The host int mask register is used to enable/disable interrupt.  However,
+ * I have the suspicion that disabled interrupts are lost.
+ */
 #define IF_CS_HOST_INT_MASK		0x00000004
 
+/*
+ * Used to send or receive data packets:
+ */
 #define IF_CS_HOST_WRITE		0x00000016
 #define IF_CS_HOST_WRITE_LEN		0x00000014
-
-#define IF_CS_HOST_CMD			0x0000001A
-#define IF_CS_HOST_CMD_LEN		0x00000018
-
 #define IF_CS_READ			0x00000010
 #define IF_CS_READ_LEN			0x00000024
 
+/*
+ * Used to send commands (and to send firmware block) and to
+ * receive command responses:
+ */
+#define IF_CS_HOST_CMD			0x0000001A
+#define IF_CS_HOST_CMD_LEN		0x00000018
 #define IF_CS_CARD_CMD			0x00000012
 #define IF_CS_CARD_CMD_LEN		0x00000030
 
+/*
+ * The card status registers shows what the card/firmware actually
+ * accepts:
+ *
+ *   IF_CS_BIT_TX        you may send a data packet
+ *   IF_CS_BIT_RX        you may retrieve a data packet
+ *   IF_CS_BIT_COMMAND   you may send a command
+ *   IF_CS_BIT_RESP      you may retrieve a command response
+ *   IF_CS_BIT_EVENT     the card has a event for use (link lost, snr low etc)
+ *
+ * When reading this register several times, you will get back the same
+ * results --- with one exception: the IF_CS_BIT_EVENT clear itself
+ * automatically.
+ *
+ * Not that we don't rely on BIT_RX,_BIT_RESP or BIT_EVENT because
+ * we handle this via the card int cause register.
+ */
 #define IF_CS_CARD_STATUS		0x00000020
 #define IF_CS_CARD_STATUS_MASK		0x7f00
 
+/*
+ * The card int cause register is used by the card/firmware to notify us
+ * about the following events:
+ *
+ *   IF_CS_BIT_TX        a data packet has successfully been sentx
+ *   IF_CS_BIT_RX        a data packet has been received and can be retrieved
+ *   IF_CS_BIT_COMMAND   not used
+ *   IF_CS_BIT_RESP      the firmware has a command response for us
+ *   IF_CS_BIT_EVENT     the card has a event for use (link lost, snr low etc)
+ */
 #define IF_CS_CARD_INT_CAUSE		0x00000022
 
+/*
+ * This is used to for handshaking with the card's bootloader/helper image
+ * to synchronize downloading of firmware blocks.
+ */
 #define IF_CS_CARD_SQ_READ_LOW		0x00000028
 #define IF_CS_CARD_SQ_HELPER_OK		0x10
 
+/*
+ * The scratch register tells us ...
+ *
+ * IF_CS_SCRATCH_BOOT_OK     the bootloader runs
+ * IF_CS_SCRATCH_HELPER_OK   the helper firmware already runs
+ */
 #define IF_CS_SCRATCH			0x0000003F
-
+#define IF_CS_SCRATCH_BOOT_OK		0x00
+#define IF_CS_SCRATCH_HELPER_OK		0x5a
 
 
 /********************************************************************/
@@ -465,11 +536,11 @@ static int if_cs_prog_helper(struct if_cs_card *card)
 	/* "If the value is 0x5a, the firmware is already
 	 * downloaded successfully"
 	 */
-	if (scratch == 0x5a)
+	if (scratch == IF_CS_SCRATCH_HELPER_OK)
 		goto done;
 
 	/* "If the value is != 00, it is invalid value of register */
-	if (scratch != 0x00) {
+	if (scratch != IF_CS_SCRATCH_BOOT_OK) {
 		ret = -ENODEV;
 		goto done;
 	}