Re: [PATCH v2] MdeModulePkg/AtaAtapiPassThru: Ensure GHC.AE bit is always set in Ahci

["Tian, Feng" <feng.tian@intel.com>]

Reviewed-by: Feng Tian <feng.tian@intel.com>

Do you want me to push it into EDKII trunk?

Thanks
Feng

-----Original Message-----
From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Marcin Wojtas
Sent: Thursday, November 24, 2016 3:55 PM
To: edk2-devel@lists.01.org
Cc: Tian, Feng <feng.tian@intel.com>; ard.biesheuvel@linaro.org; leif.lindholm@linaro.org; Gao, Liming <liming.gao@intel.com>; Kinney, Michael D <michael.d.kinney@intel.com>
Subject: [edk2] [PATCH v2] MdeModulePkg/AtaAtapiPassThru: Ensure GHC.AE bit is always set in Ahci

According to AHCI Spec 1.3 GHC.AE bit description:
"The implementation of this bit is dependent upon the value of the CAP.SAM bit. If CAP.SAM is '0', then GHC.AE shall be read-write and shall have a reset value of '0'. If CAP.SAM is '1', then AE shall be read-only and shall have a reset value of '1'."

Being in AhciMode, for proper operation it is required, that GHC.AE bit is always set, before any other AHCI registers are written to. Current AhciMode implementation, both in AhciReset() and AhciModeInitialization() functions, set GHC.AE bit only depending on 'CAP.SAM == 0' condition, assuming (according to the AHCI spec), that otherwise it has to be set anyway. It may however happen, that even if 'CAP.SAM == 1', GHC.AE requires updating by software.

This patch enables in AhciMode setting GHC.AE in case its initial value is '0'. It fixes AHCI support for Marvell Armada 70x0 and 80x0 SoC families. The change is transparent to all other platforms.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Marcin Wojtas <mw@semihalf.com>
Signed-off-by: Jan Dabros <jsd@semihalf.com>

---
Changelog:
v1 -> v2

* Instead of doing it uncoditionally, enable setting GHC.AE bit only in
  case its initial value is '0'

---
 MdeModulePkg/Bus/Ata/AtaAtapiPassThru/AhciMode.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/MdeModulePkg/Bus/Ata/AtaAtapiPassThru/AhciMode.c b/MdeModulePkg/Bus/Ata/AtaAtapiPassThru/AhciMode.c
index 533d201..4d01c1d 100644
--- a/MdeModulePkg/Bus/Ata/AtaAtapiPassThru/AhciMode.c
+++ b/MdeModulePkg/Bus/Ata/AtaAtapiPassThru/AhciMode.c
@@ -1451,17 +1451,13 @@ AhciReset (
 {
   UINT64                 Delay;
   UINT32                 Value;
-  UINT32                 Capability;
 
   //
-  // Collect AHCI controller information
-  //
-  Capability = AhciReadReg (PciIo, EFI_AHCI_CAPABILITY_OFFSET);
-
-  //
-  // Enable AE before accessing any AHCI registers if Supports AHCI Mode Only is not set
+  // Make sure that GHC.AE bit is set before accessing any AHCI registers.
   //
-  if ((Capability & EFI_AHCI_CAP_SAM) == 0) {
+  Value = AhciReadReg(PciIo, EFI_AHCI_GHC_OFFSET);
+
+  if ((Value & EFI_AHCI_GHC_ENABLE) == 0) {
     AhciOrReg (PciIo, EFI_AHCI_GHC_OFFSET, EFI_AHCI_GHC_ENABLE);
   }
 
@@ -2252,6 +2248,7 @@ AhciModeInitialization (
   EFI_ATA_COLLECTIVE_MODE          *SupportedModes;
   EFI_ATA_TRANSFER_MODE            TransferMode;
   UINT32                           PhyDetectDelay;
+  UINT32                           Value;
 
   if (Instance == NULL) {
     return EFI_INVALID_PARAMETER;
@@ -2270,11 +2267,13 @@ AhciModeInitialization (
   // Collect AHCI controller information
   //
   Capability = AhciReadReg (PciIo, EFI_AHCI_CAPABILITY_OFFSET);
-  
+
   //
-  // Enable AE before accessing any AHCI registers if Supports AHCI Mode Only is not set
+  // Make sure that GHC.AE bit is set before accessing any AHCI registers.
   //
-  if ((Capability & EFI_AHCI_CAP_SAM) == 0) {
+  Value = AhciReadReg(PciIo, EFI_AHCI_GHC_OFFSET);
+
+  if ((Value & EFI_AHCI_GHC_ENABLE) == 0) {
     AhciOrReg (PciIo, EFI_AHCI_GHC_OFFSET, EFI_AHCI_GHC_ENABLE);
   }
 
--
1.8.3.1

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