[SCSI] wd33c93: Fast SCSI with WD33C93B

Attached are patches, which help to utilize more of the WD33C93B SCSI
controller's capabilities.

1) Added/changed all the necessary code to enable Burst Mode DMA. Only
   Single Byte DMA was used before.

2) Added/changed all the necessary code to enable Fast-10 SCSI transfers.

3) The original driver inadvertently used a transfer period of 1000-800ns
   (the lowest possible transfer rate) for asynchronous data transfers,
   instead of the (configurable) default period intended for this purpose,
   if the target responded to a SDTR not with a Reject-message, but with
   a zero-SDTR. This issue was fixed.
   Moreover, in case of a Reject the driver used the default-period's
   initialization-value instead of its (maybe smaller) current value. The
   missing assignment was added.

4) The driver's commandline- and proc-file-interface was augmented to
   handle the new options properly.

The WD33C93 manual, found at
http://www.datasheet.in/datasheet-html/W/D/3/WD33C93B_WesternDigital.pdf.html,
was very helpful.

Signed-off-by: peter fuerst <post@pfrst.de>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/wd33c93.h

@@ -155,6 +155,9 @@
 #define WD33C93_FS_12_15 OWNID_FS_12
 #define WD33C93_FS_16_20 OWNID_FS_16
 
+   /* pass input-clock explicitely. accepted mhz values are 8-10,12-20 */
+#define WD33C93_FS_MHZ(mhz) (mhz)
+
    /* Control register */
 #define CTRL_HSP     0x01
 #define CTRL_HA      0x02
@@ -253,6 +256,9 @@ struct WD33C93_hostdata {
     uchar            sync_stat[8];     /* status of sync negotiation per target */
     uchar            no_sync;          /* bitmask: don't do sync on these targets */
     uchar            no_dma;           /* set this flag to disable DMA */
+    uchar            dma_mode;         /* DMA Burst Mode or Single Byte DMA */
+    uchar            fast;             /* set this flag to enable Fast SCSI */
+    struct sx_period sx_table[9];      /* transfer periods for actual DTC-setting */
 #ifdef PROC_INTERFACE
     uchar            proc;             /* bitmask: what's in proc output */
 #ifdef PROC_STATISTICS