[Xen-devel] [Patch 2/5] rombios/ata: Do not wait for BSY to be set

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

After issuing a reset, the BSY bit is expected to be set.  This is not the
case for Qemu.

In SeaBIOS.git: 580e33293244fee4556e56ecc67b8bd877f3c496

this check was even replaced with a udelay(5), as enough real hardware ignored
the BSY bit as well.

As rombios does not have an equivalent udelay(), replace the wait with a write
to port 0x80 which is whitelisted by Xen for 'a small delay'.

This causes 42k fewer IO traps to Qemu.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: Keir Fraser <keir@xxxxxxx>
---
 tools/firmware/rombios/rombios.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/firmware/rombios/rombios.c b/tools/firmware/rombios/rombios.c
index e364759..a3efc61 100644
--- a/tools/firmware/rombios/rombios.c
+++ b/tools/firmware/rombios/rombios.c
@@ -2914,8 +2914,8 @@ Bit16u device;
 // 8.2.1 (a) -- set SRST in DC
   outb(iobase2+ATA_CB_DC, ATA_CB_DC_HD15 | ATA_CB_DC_NIEN | ATA_CB_DC_SRST);
 
-// 8.2.1 (b) -- wait for BSY
-  await_ide(BSY, iobase1, 20);
+// 8.2.1 (b) -- wait
+  outb(0x80, 0x00);
 
 // 8.2.1 (f) -- clear SRST
   outb(iobase2+ATA_CB_DC, ATA_CB_DC_HD15 | ATA_CB_DC_NIEN);
-- 
1.7.10.4


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel