I think you are right

Reviewed-by: Feng Tian <[email protected]>

-----Original Message-----
From: edk2-devel [mailto:[email protected]] On Behalf Of Cinnamon 
Shia
Sent: Monday, June 6, 2016 12:08 PM
To: [email protected]
Cc: Wu, Hao A <[email protected]>; [email protected]; Tian, Feng 
<[email protected]>; Zeng, Star <[email protected]>
Subject: [edk2] [PATCH] MdeModulePkg/AtaBusDxe: Fix some ATA hard drives cannot 
be discovered

If there is no multiplier, the DEV bit of the ATA device register would always 
be set. It causes that some ATA hard drives don't response the ATA identity 
command sent to them.

Below is the description about DEV bit in ATA spec:
A device is selected when the DEV bit of the Device register is equal to the 
device number assigned to the device by means of a Device 0/Device 1 jumper or 
switch, or use of the CSEL signal.

Below is the description about DEV bit in SATA spec:
When the DEV bit in the Device register is set to one, selecting the 
non-existent Device 1, the host adapter shall respond to register reads and 
writes as specified for a Device 0 with no Device 1 present, as defined in the 
ATA/ATAPI-5 standard.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Cinnamon Shia <[email protected]>
---
 MdeModulePkg/Bus/Ata/AtaBusDxe/AtaPassThruExecute.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/MdeModulePkg/Bus/Ata/AtaBusDxe/AtaPassThruExecute.c 
b/MdeModulePkg/Bus/Ata/AtaBusDxe/AtaPassThruExecute.c
index a3008f9..a3739fc 100644
--- a/MdeModulePkg/Bus/Ata/AtaBusDxe/AtaPassThruExecute.c
+++ b/MdeModulePkg/Bus/Ata/AtaBusDxe/AtaPassThruExecute.c
@@ -11,6 +11,7 @@
   Cylinder register.
 
   Copyright (c) 2009 - 2013, Intel Corporation. All rights reserved.<BR>
+  (C) Copyright 2016 Hewlett Packard Enterprise Development LP<BR>
   This program and the accompanying materials
   are licensed and made available under the terms and conditions of the BSD 
License
   which accompanies this distribution.  The full text of the license may be 
found at @@ -413,7 +414,7 @@ DiscoverAtaDevice (
   //
   Acb = ZeroMem (&AtaDevice->Acb, sizeof (EFI_ATA_COMMAND_BLOCK));
   Acb->AtaCommand = ATA_CMD_IDENTIFY_DRIVE;
-  Acb->AtaDeviceHead = (UINT8) (BIT7 | BIT6 | BIT5 | 
(AtaDevice->PortMultiplierPort << 4));
+  Acb->AtaDeviceHead = (UINT8) (BIT7 | BIT6 | BIT5 | 
+ (AtaDevice->PortMultiplierPort == 0xFFFF ? 0 : 
+ (AtaDevice->PortMultiplierPort << 4)));
 
   //
   // Prepare for ATA pass through packet.
--
2.8.1.windows.1

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