iwlwifi: document Rx registers

Document Rx registers

Document Tx circular buffer base registers
Signed-off-by: Ben Cahill <ben.m.cahill@intel.com>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-4965-hw.h

@@ -1286,7 +1286,7 @@ enum {
 /* Flow Handler Definitions */
 /****************************/
 
-/*
+/**
  * This I/O area is directly read/writable by driver (e.g. Linux uses writel())
  * Addresses are offsets from device's PCI hardware base address.
  */
@@ -1313,35 +1313,193 @@ enum {
 #define IWL_FH_KW_MEM_ADDR_REG		     (FH_MEM_LOWER_BOUND + 0x97C)
 
 
-/* CBBC Area - Circular buffers base address cache pointers table */
+/**
+ * TFD Circular Buffers Base (CBBC) addresses
+ *
+ * 4965 has 16 base pointer registers, one for each of 16 host-DRAM-resident
+ * circular buffers (CBs/queues) containing Transmit Frame Descriptors (TFDs)
+ * (see struct iwl_tfd_frame).  These 16 pointer registers are offset by 0x04
+ * bytes from one another.  Each TFD circular buffer in DRAM must be 256-byte
+ * aligned (address bits 0-7 must be 0).
+ *
+ * Bit fields in each pointer register:
+ *  27-0: TFD CB physical base address [35:8], must be 256-byte aligned
+ */
 #define FH_MEM_CBBC_LOWER_BOUND              (FH_MEM_LOWER_BOUND + 0x9D0)
 #define FH_MEM_CBBC_UPPER_BOUND              (FH_MEM_LOWER_BOUND + 0xA10)
-/* queues 0 - 15 */
+
+/* Find TFD CB base pointer for given queue (range 0-15). */
 #define FH_MEM_CBBC_QUEUE(x)  (FH_MEM_CBBC_LOWER_BOUND + (x) * 0x4)
 
-/* RSCSR Area */
+
+/**
+ * Rx SRAM Control and Status Registers (RSCSR)
+ *
+ * These registers provide handshake between driver and 4965 for the Rx queue
+ * (this queue handles *all* command responses, notifications, Rx data, etc.
+ * sent from 4965 uCode to host driver).  Unlike Tx, there is only one Rx
+ * queue, and only one Rx DMA/FIFO channel.  Also unlike Tx, which can
+ * concatenate up to 20 DRAM buffers to form a Tx frame, each Receive Buffer
+ * Descriptor (RBD) points to only one Rx Buffer (RB); there is a 1:1
+ * mapping between RBDs and RBs.
+ *
+ * Driver must allocate host DRAM memory for the following, and set the
+ * physical address of each into 4965 registers:
+ *
+ * 1)  Receive Buffer Descriptor (RBD) circular buffer (CB), typically with 256
+ *     entries (although any power of 2, up to 4096, is selectable by driver).
+ *     Each entry (1 dword) points to a receive buffer (RB) of consistent size
+ *     (typically 4K, although 8K or 16K are also selectable by driver).
+ *     Driver sets up RB size and number of RBDs in the CB via Rx config
+ *     register FH_MEM_RCSR_CHNL0_CONFIG_REG.
+ *
+ *     Bit fields within one RBD:
+ *     27-0:  Receive Buffer physical address bits [35:8], 256-byte aligned
+ *
+ *     Driver sets physical address [35:8] of base of RBD circular buffer
+ *     into FH_RSCSR_CHNL0_RBDCB_BASE_REG [27:0].
+ *
+ * 2)  Rx status buffer, 8 bytes, in which 4965 indicates which Rx Buffers
+ *     (RBs) have been filled, via a "write pointer", actually the index of
+ *     the RB's corresponding RBD within the circular buffer.  Driver sets
+ *     physical address [35:4] into FH_RSCSR_CHNL0_STTS_WPTR_REG [31:0].
+ *
+ *     Bit fields in lower dword of Rx status buffer (upper dword not used
+ *     by driver; see struct iwl4965_shared, val0):
+ *     31-12:  Not used by driver
+ *     11- 0:  Index of last filled Rx buffer descriptor
+ *             (4965 writes, driver reads this value)
+ *
+ * As the driver prepares Receive Buffers (RBs) for 4965 to fill, driver must
+ * enter pointers to these RBs into contiguous RBD circular buffer entries,
+ * and update the 4965's "write" index register, FH_RSCSR_CHNL0_RBDCB_WPTR_REG.
+ *
+ * This "write" index corresponds to the *next* RBD that the driver will make
+ * available, i.e. one RBD past the tail of the ready-to-fill RBDs within
+ * the circular buffer.  This value should initially be 0 (before preparing any
+ * RBs), should be 8 after preparing the first 8 RBs (for example), and must
+ * wrap back to 0 at the end of the circular buffer (but don't wrap before
+ * "read" index has advanced past 1!  See below).
+ * NOTE:  4965 EXPECTS THE WRITE INDEX TO BE INCREMENTED IN MULTIPLES OF 8.
+ *
+ * As the 4965 fills RBs (referenced from contiguous RBDs within the circular
+ * buffer), it updates the Rx status buffer in host DRAM, 2) described above,
+ * to tell the driver the index of the latest filled RBD.  The driver must
+ * read this "read" index from DRAM after receiving an Rx interrupt from 4965.
+ *
+ * The driver must also internally keep track of a third index, which is the
+ * next RBD to process.  When receiving an Rx interrupt, driver should process
+ * all filled but unprocessed RBs up to, but not including, the RB
+ * corresponding to the "read" index.  For example, if "read" index becomes "1",
+ * driver may process the RB pointed to by RBD 0.  Depending on volume of
+ * traffic, there may be many RBs to process.
+ *
+ * If read index == write index, 4965 thinks there is no room to put new data.
+ * Due to this, the maximum number of filled RBs is 255, instead of 256.  To
+ * be safe, make sure that there is a gap of at least 2 RBDs between "write"
+ * and "read" indexes; that is, make sure that there are no more than 254
+ * buffers waiting to be filled.
+ */
 #define FH_MEM_RSCSR_LOWER_BOUND	(FH_MEM_LOWER_BOUND + 0xBC0)
 #define FH_MEM_RSCSR_UPPER_BOUND	(FH_MEM_LOWER_BOUND + 0xC00)
 #define FH_MEM_RSCSR_CHNL0		(FH_MEM_RSCSR_LOWER_BOUND)
 
+/**
+ * Physical base address of 8-byte Rx Status buffer.
+ * Bit fields:
+ *  31-0: Rx status buffer physical base address [35:4], must 16-byte aligned.
+ */
 #define FH_RSCSR_CHNL0_STTS_WPTR_REG		(FH_MEM_RSCSR_CHNL0)
+
+/**
+ * Physical base address of Rx Buffer Descriptor Circular Buffer.
+ * Bit fields:
+ *  27-0:  RBD CD physical base address [35:8], must be 256-byte aligned.
+ */
 #define FH_RSCSR_CHNL0_RBDCB_BASE_REG		(FH_MEM_RSCSR_CHNL0 + 0x004)
+
+/**
+ * Rx write pointer (index, really!).
+ * Bit fields:
+ *  11-0:  Index of driver's most recent prepared-to-be-filled RBD, + 1.
+ *         NOTE:  For 256-entry circular buffer, use only bits [7:0].
+ */
 #define FH_RSCSR_CHNL0_RBDCB_WPTR_REG		(FH_MEM_RSCSR_CHNL0 + 0x008)
 
-/* RCSR Area - Registers address map */
+
+/**
+ * Rx Config/Status Registers (RCSR)
+ * Rx Config Reg for channel 0 (only channel used)
+ *
+ * Driver must initialize FH_MEM_RCSR_CHNL0_CONFIG_REG as follows for
+ * normal operation (see bit fields).
+ *
+ * Clearing FH_MEM_RCSR_CHNL0_CONFIG_REG to 0 turns off Rx DMA.
+ * Driver should poll FH_MEM_RSSR_RX_STATUS_REG	for
+ * FH_RSSR_CHNL0_RX_STATUS_CHNL_IDLE (bit 24) before continuing.
+ *
+ * Bit fields:
+ * 31-30: Rx DMA channel enable: '00' off/pause, '01' pause at end of frame,
+ *        '10' operate normally
+ * 29-24: reserved
+ * 23-20: # RBDs in circular buffer = 2^value; use "8" for 256 RBDs (normal),
+ *        min "5" for 32 RBDs, max "12" for 4096 RBDs.
+ * 19-18: reserved
+ * 17-16: size of each receive buffer; '00' 4K (normal), '01' 8K,
+ *        '10' 12K, '11' 16K.
+ * 15-14: reserved
+ * 13-12: IRQ destination; '00' none, '01' host driver (normal operation)
+ * 11- 4: timeout for closing Rx buffer and interrupting host (units 32 usec)
+ *        typical value 0x10 (about 1/2 msec)
+ *  3- 0: reserved
+ */
 #define FH_MEM_RCSR_LOWER_BOUND      (FH_MEM_LOWER_BOUND + 0xC00)
 #define FH_MEM_RCSR_UPPER_BOUND      (FH_MEM_LOWER_BOUND + 0xCC0)
 #define FH_MEM_RCSR_CHNL0            (FH_MEM_RCSR_LOWER_BOUND)
 
 #define FH_MEM_RCSR_CHNL0_CONFIG_REG	(FH_MEM_RCSR_CHNL0)
 
-/* RSSR Area - Rx shared ctrl & status registers */
+#define FH_RCSR_CHNL0_RX_CONFIG_RB_TIMEOUT_MASK   (0x00000FF0) /* bit 4-11 */
+#define FH_RCSR_CHNL0_RX_CONFIG_IRQ_DEST_MASK     (0x00001000) /* bit 12 */
+#define FH_RCSR_CHNL0_RX_CONFIG_SINGLE_FRAME_MASK (0x00008000) /* bit 15 */
+#define FH_RCSR_CHNL0_RX_CONFIG_RB_SIZE_MASK	  (0x00030000) /* bits 16-17 */
+#define FH_RCSR_CHNL0_RX_CONFIG_RBDBC_SIZE_MASK   (0x00F00000) /* bits 20-23 */
+#define FH_RCSR_CHNL0_RX_CONFIG_DMA_CHNL_EN_MASK  (0xC0000000) /* bits 30-31 */
+
+#define FH_RCSR_RX_CONFIG_RBDCB_SIZE_BITSHIFT	(20)
+#define FH_RCSR_RX_CONFIG_RB_SIZE_BITSHIFT	(16)
+
+#define FH_RCSR_RX_CONFIG_CHNL_EN_PAUSE_VAL         (0x00000000)
+#define FH_RCSR_RX_CONFIG_CHNL_EN_PAUSE_EOF_VAL     (0x40000000)
+#define FH_RCSR_RX_CONFIG_CHNL_EN_ENABLE_VAL        (0x80000000)
+
+#define IWL_FH_RCSR_RX_CONFIG_REG_VAL_RB_SIZE_4K    (0x00000000)
+
+#define FH_RCSR_CHNL0_RX_CONFIG_IRQ_DEST_NO_INT_VAL       (0x00000000)
+#define FH_RCSR_CHNL0_RX_CONFIG_IRQ_DEST_INT_HOST_VAL     (0x00001000)
+
+
+/**
+ * Rx Shared Status Registers (RSSR)
+ *
+ * After stopping Rx DMA channel (writing 0 to FH_MEM_RCSR_CHNL0_CONFIG_REG),
+ * driver must poll FH_MEM_RSSR_RX_STATUS_REG until Rx channel is idle.
+ *
+ * Bit fields:
+ *  24:  1 = Channel 0 is idle
+ *
+ * FH_MEM_RSSR_SHARED_CTRL_REG and FH_MEM_RSSR_RX_ENABLE_ERR_IRQ2DRV contain
+ * default values that should not be altered by the driver.
+ */
 #define FH_MEM_RSSR_LOWER_BOUND                	(FH_MEM_LOWER_BOUND + 0xC40)
 #define FH_MEM_RSSR_UPPER_BOUND               	(FH_MEM_LOWER_BOUND + 0xD00)
+
 #define FH_MEM_RSSR_SHARED_CTRL_REG           	(FH_MEM_RSSR_LOWER_BOUND)
 #define FH_MEM_RSSR_RX_STATUS_REG	(FH_MEM_RSSR_LOWER_BOUND + 0x004)
 #define FH_MEM_RSSR_RX_ENABLE_ERR_IRQ2DRV  (FH_MEM_RSSR_LOWER_BOUND + 0x008)
 
+#define FH_RSSR_CHNL0_RX_STATUS_CHNL_IDLE	(0x01000000)
+
 /* TCSR */
 #define IWL_FH_TCSR_LOWER_BOUND  (FH_MEM_LOWER_BOUND + 0xD00)
 #define IWL_FH_TCSR_UPPER_BOUND  (FH_MEM_LOWER_BOUND + 0xE60)
@@ -1369,17 +1527,6 @@ enum {
 
 #define IWL_FH_TCSR_TX_CONFIG_REG_VAL_DMA_CHNL_ENABLE           (0x80000000)
 
-/* RCSR:  channel 0 rx_config register defines */
-
-#define FH_RCSR_RX_CONFIG_RBDCB_SIZE_BITSHIFT       (20)
-
-#define FH_RCSR_RX_CONFIG_CHNL_EN_ENABLE_VAL        (0x80000000)
-
-#define IWL_FH_RCSR_RX_CONFIG_REG_VAL_RB_SIZE_4K    (0x00000000)
-
-/* RCSR channel 0 config register values */
-#define FH_RCSR_CHNL0_RX_CONFIG_IRQ_DEST_INT_HOST_VAL     (0x00001000)
-
 #define SCD_WIN_SIZE				64
 #define SCD_FRAME_LIMIT				64