[PATCH] MdeModulePkg SataControllerDxe: Calculate ChannelCount based on PI value

[Star Zeng <star.zeng@intel.com>]

Current code calculates ChannelCount based on CAP(NP) value.
It only works when the ports implemented number are <= CAP(NP),
for example, platform has CAP(NP) = 5 (means 6 ports) and ports
implemented are 0, 1, 2, 3, 4 and 5.

But we have some platform that has CAP(NP) = 1 (means 2 ports) and
ports implemented are 1 and 2, and has no port 0 implemented, then
current code does not work.

This patch updates the code to calculate ChannelCount based on PI value.

Cc: Amy Chan <amy.chan@intel.com>
Cc: Hong-chihX Hsueh <hong-chihx.hsueh@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Sami Mujawar <sami.mujawar@arm.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Hao Wu <hao.a.wu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Star Zeng <star.zeng@intel.com>
---
 .../Bus/Pci/SataControllerDxe/SataController.c     | 28 ++++++++++++++++++----
 .../Bus/Pci/SataControllerDxe/SataController.h     |  1 +
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/MdeModulePkg/Bus/Pci/SataControllerDxe/SataController.c b/MdeModulePkg/Bus/Pci/SataControllerDxe/SataController.c
index 7dc40f82e819..d47e918f5757 100644
--- a/MdeModulePkg/Bus/Pci/SataControllerDxe/SataController.c
+++ b/MdeModulePkg/Bus/Pci/SataControllerDxe/SataController.c
@@ -366,6 +366,7 @@ SataControllerStart (
   UINT32                            Data32;
   UINTN                             TotalCount;
   UINT64                            Supports;
+  UINT8                             MaxPortNumber;
 
   DEBUG ((EFI_D_INFO, "SataControllerStart start\n"));
 
@@ -472,12 +473,31 @@ SataControllerStart (
     Private->DeviceCount          = IDE_MAX_DEVICES;
   } else if (IS_PCI_SATADPA (&PciData)) {
     //
-    // Read Host Capability Register(CAP) to get Number of Ports(NPS) and Supports Port Multiplier(SPM)
-    //   NPS is 0's based value indicating the maximum number of ports supported by the HBA silicon.
-    //   A maximum of 32 ports can be supported. A value of '0h', indicating one port, is the minimum requirement.
+    // Read Ports Implemented(PI) to calculate max port number (0 based).
+    //
+    Data32 = AhciReadReg (PciIo, R_AHCI_PI);
+    DEBUG ((DEBUG_INFO, "Ports Implemented(PI) = 0x%x\n", Data32));
+    if (Data32 == 0) {
+      Status = EFI_UNSUPPORTED;
+      goto Done;
+    }
+    MaxPortNumber = 31;
+    while (MaxPortNumber > 0) {
+      if (Data32 & (1 << MaxPortNumber)) {
+        break;
+      }
+      MaxPortNumber--;
+    }
+    //
+    // Make the ChannelCount equal to the max port number (0 based) plus 1.
+    //
+    Private->IdeInit.ChannelCount = MaxPortNumber + 1;
+
+    //
+    // Read HBA Capabilities(CAP) to get Supports Port Multiplier(SPM).
     //
     Data32 = AhciReadReg (PciIo, R_AHCI_CAP);
-    Private->IdeInit.ChannelCount = (UINT8) ((Data32 & B_AHCI_CAP_NPS) + 1);
+    DEBUG ((DEBUG_INFO, "HBA Capabilities(CAP) = 0x%x\n", Data32));
     Private->DeviceCount          = AHCI_MAX_DEVICES;
     if ((Data32 & B_AHCI_CAP_SPM) == B_AHCI_CAP_SPM) {
       Private->DeviceCount = AHCI_MULTI_MAX_DEVICES;
diff --git a/MdeModulePkg/Bus/Pci/SataControllerDxe/SataController.h b/MdeModulePkg/Bus/Pci/SataControllerDxe/SataController.h
index 436eff2dc673..7ffd3e218a61 100644
--- a/MdeModulePkg/Bus/Pci/SataControllerDxe/SataController.h
+++ b/MdeModulePkg/Bus/Pci/SataControllerDxe/SataController.h
@@ -44,6 +44,7 @@ extern EFI_COMPONENT_NAME2_PROTOCOL gSataControllerComponentName2;
 #define R_AHCI_CAP 0x0
 #define   B_AHCI_CAP_NPS (BIT4 | BIT3 | BIT2 | BIT1 | BIT0) // Number of Ports
 #define   B_AHCI_CAP_SPM BIT17                              // Supports Port Multiplier
+#define R_AHCI_PI  0xC
 
 ///
 /// AHCI each channel can have up to 1 device
-- 
2.7.0.windows.1