[Xen-devel] [Patch 4/5] rombios/ata Remove another needless trap from the int 0x13 hotpath

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

The return value from await_ide() is always ignored, and most calls to 
await_ide()
immediately reread the status register.

Therefore, making await_ide() return the last value of the status register 
removes
a further two traps on the int 0x13 path.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: Keir Fraser <keir@xxxxxxx>
---
 tools/firmware/rombios/rombios.c |   32 +++++++++++++-------------------
 1 file changed, 13 insertions(+), 19 deletions(-)

diff --git a/tools/firmware/rombios/rombios.c b/tools/firmware/rombios/rombios.c
index f555747..057aced 100644
--- a/tools/firmware/rombios/rombios.c
+++ b/tools/firmware/rombios/rombios.c
@@ -2531,14 +2531,14 @@ void ata_init( )
 
 #define IDE_TIMEOUT 32000u //32 seconds max for IDE ops
 
-int await_ide();
-static int await_ide(when_done,base,timeout)
+Bit8u await_ide();
+static Bit8u await_ide(when_done,base,timeout)
   Bit8u when_done;
   Bit16u base;
   Bit16u timeout;
 {
   Bit32u time=0,last=0;
-  Bit16u status;
+  Bit8u status;
   Bit8u result;
   for(;;) {
     status = inb(base+ATA_CB_STAT);
@@ -2556,7 +2556,7 @@ static int await_ide(when_done,base,timeout)
     else if (when_done == TIMEOUT)
       result = 0;
 
-    if (result) return 0;
+    if (result) return status;
     if (time>>16 != last) // mod 2048 each 16 ms
     {
       last = time >>16;
@@ -2565,12 +2565,12 @@ static int await_ide(when_done,base,timeout)
     if (status & ATA_CB_STAT_ERR)
     {
       BX_DEBUG_ATA("await_ide: ERROR 
(TIMEOUT,BSY,!BSY,!BSY_DRQ,!BSY_!DRQ,!BSY_RDY) %d time= %ld timeout= 
%d\n",when_done,time>>11, timeout);
-      return -1;
+      return status;
     }
     if ((timeout == 0) || ((time>>11) > timeout)) break;
   }
   BX_INFO("IDE time out\n");
-  return -1;
+  return status;
 }
 
 // ---------------------------------------------------------------------------
@@ -3016,8 +3016,7 @@ Bit32u lba_low, lba_high;
   outb(iobase1 + ATA_CB_DH, (slave ? ATA_CB_DH_DEV1 : ATA_CB_DH_DEV0) | 
(Bit8u) head );
   outb(iobase1 + ATA_CB_CMD, command);
 
-  await_ide(NOT_BSY_DRQ, iobase1, IDE_TIMEOUT);
-  status = inb(iobase1 + ATA_CB_STAT);
+  status = await_ide(NOT_BSY_DRQ, iobase1, IDE_TIMEOUT);
 
   if (status & ATA_CB_STAT_ERR) {
     BX_DEBUG_ATA("ata_cmd_data_in : read error\n");
@@ -3077,8 +3076,7 @@ ASM_END
     current++;
     write_word(ebda_seg, &EbdaData->ata.trsfsectors,current);
     count--;
-    await_ide(NOT_BSY, iobase1, IDE_TIMEOUT);
-    status = inb(iobase1 + ATA_CB_STAT);
+    status = await_ide(NOT_BSY, iobase1, IDE_TIMEOUT);
     if (count == 0) {
       if ( (status & (ATA_CB_STAT_BSY | ATA_CB_STAT_RDY | ATA_CB_STAT_DRQ | 
ATA_CB_STAT_ERR) )
           != ATA_CB_STAT_RDY ) {
@@ -3167,8 +3165,7 @@ Bit32u lba_low, lba_high;
   outb(iobase1 + ATA_CB_DH, (slave ? ATA_CB_DH_DEV1 : ATA_CB_DH_DEV0) | 
(Bit8u) head );
   outb(iobase1 + ATA_CB_CMD, command);
 
-  await_ide(NOT_BSY_DRQ, iobase1, IDE_TIMEOUT);
-  status = inb(iobase1 + ATA_CB_STAT);
+  status = await_ide(NOT_BSY_DRQ, iobase1, IDE_TIMEOUT);
 
   if (status & ATA_CB_STAT_ERR) {
     BX_DEBUG_ATA("ata_cmd_data_out : read error\n");
@@ -3316,8 +3313,7 @@ Bit32u length;
   outb(iobase1 + ATA_CB_CMD, ATA_CMD_PACKET);
 
   // Device should ok to receive command
-  await_ide(NOT_BSY_DRQ, iobase1, IDE_TIMEOUT);
-  status = inb(iobase1 + ATA_CB_STAT);
+  status = await_ide(NOT_BSY_DRQ, iobase1, IDE_TIMEOUT);
 
   if (status & ATA_CB_STAT_ERR) {
     BX_DEBUG_ATA("ata_cmd_packet : error, status is %02x\n",status);
@@ -3353,8 +3349,7 @@ ASM_START
 ASM_END
 
   if (inout == ATA_DATA_NO) {
-    await_ide(NOT_BSY, iobase1, IDE_TIMEOUT);
-    status = inb(iobase1 + ATA_CB_STAT);
+    status = await_ide(NOT_BSY, iobase1, IDE_TIMEOUT);
     }
   else {
         Bit16u loops = 0;
@@ -3363,13 +3358,12 @@ ASM_END
 
       if (loops == 0) {//first time through
         status = inb(iobase2 + ATA_CB_ASTAT);
-        await_ide(NOT_BSY_DRQ, iobase1, IDE_TIMEOUT);
+        status = await_ide(NOT_BSY_DRQ, iobase1, IDE_TIMEOUT);
       }
       else
-        await_ide(NOT_BSY, iobase1, IDE_TIMEOUT);
+        status = await_ide(NOT_BSY, iobase1, IDE_TIMEOUT);
       loops++;
 
-      status = inb(iobase1 + ATA_CB_STAT);
       sc = inb(iobase1 + ATA_CB_SC);
 
       // Check if command completed
-- 
1.7.10.4


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