rombios: add support for special CHS layout (spt=32)

[DuanZhenzhong <zhenzhong.duan@oracle.com>]

When booting up windows VM which converted by dd scsi disk, it fails with
"Error Loading Operating System", root cause is rombios doesn't simulate disk's
logical CHS properly. Real bios uses spt=32 here.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
--- a/tools/firmware/rombios/rombios.c	2011-12-09 00:50:28.000000000 +0800
+++ b/tools/firmware/rombios/rombios.c	2012-11-20 09:42:50.000000000 +0800
@@ -2674,6 +2674,8 @@ void ata_detect( )
       Bit32u sectors_low, sectors_high;
       Bit16u cylinders, heads, spt, blksize;
       Bit8u  translation, removable, mode;
+      Bit8u i;
+      Bit8u *p;
 
       // default mode to PIO16
       mode = ATA_MODE_PIO16;
@@ -2738,14 +2740,32 @@ void ata_detect( )
         case ATA_TRANSLATION_NONE:
           break;
         case ATA_TRANSLATION_LBA:
-          spt = 63;
-          sectors_low /= 63;
-          heads = sectors_low / 1024;
-          if (heads>128) heads = 255;
-          else if (heads>64) heads = 128;
-          else if (heads>32) heads = 64;
-          else if (heads>16) heads = 32;
-          else heads=16;
+          spt = heads = 0;
+          if (ata_cmd_data_in(device,ATA_CMD_READ_SECTORS, 1, 0, 0, 1, 0L, 0L, get_SS(),buffer) !=0 )
+            BX_PANIC("ata-detect: Failed to read first sector\n");
+          for(i=0; i<4; i++) {
+            p = buffer + 0x1be + i * 16;
+            if (read_dword(get_SS(), p+12) && read_byte(get_SS(), p+5)) {
+              /* We make the assumption that the partition terminates on
+                 a cylinder boundary */
+              heads = read_byte(get_SS(), p+5) + 1;
+              spt = read_byte(get_SS(), p+6) & 63;
+              if (spt != 0)
+                break;
+            }
+          }
+          if (spt == 32) {
+            sectors_low /= spt;
+          } else {
+            spt = 63;
+            sectors_low /= 63;
+            heads = sectors_low / 1024;
+            if (heads>128) heads = 255;
+            else if (heads>64) heads = 128;
+            else if (heads>32) heads = 64;
+            else if (heads>16) heads = 32;
+            else heads=16;
+          }
           cylinders = sectors_low / heads;
           break;
         case ATA_TRANSLATION_RECHS: