MdeModulePkg/PciBusDxe: Improve the flow of testing support attributes

https://bugzilla.tianocore.org/show_bug.cgi?id=3635

Currently, in order to test the supported attributes,
the PciTestSupportedAttribute() will set the command register
to 0x27 (EFI_PCI_COMMAND_IO_SPACE, EFI_PCI_COMMAND_MEMORY_SPACE,
EFI_PCI_COMMAND_BUS_MASTER, EFI_PCI_COMMAND_VGA_PALETTE_SNOOP) firstly,
and then read back to check whether these attributes are
set successfully in the device.
This will cause the other enabled bits
 (other than EFI_PCI_COMMAND_IO_SPACE,EFI_PCI_COMMAND_MEMORY_SPACE,
 EFI_PCI_COMMAND_BUS_MASTER,EFI_PCI_COMMAND_VGA_PALETTE_SNOOP)
 be cleared for a short of time
 This patch fixes this issue by keeping the origina
 enabled bits when setting 0x27.

Signed-off-by: xueshengfeng <xueshengfeng@byosoft.com.cn>
Reviewed-by: Ray <ray.ni@intel.com>

diff --git a/MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumeratorSupport.c b/MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumeratorSupport.c
index db1b35f8ef4858b0b8a457bc7da49a82d97b3807..3a238d4e46ab4d2b3b9616790f03a94dea8d3f75 100644 (file)
--- a/MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumeratorSupport.c
+++ b/MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumeratorSupport.c
@@ -933,6 +933,7 @@ PciTestSupportedAttribute (
   )\r
 {\r
   EFI_TPL OldTpl;\r
+  UINT16  CommandValue;\r
 \r
   //\r
   // Preserve the original value\r
@@ -943,10 +944,12 @@ PciTestSupportedAttribute (
   // Raise TPL to high level to disable timer interrupt while the BAR is probed\r
   //\r
   OldTpl = gBS->RaiseTPL (TPL_HIGH_LEVEL);\r
+  CommandValue = *Command | *OldCommand;\r
 \r
-  PCI_SET_COMMAND_REGISTER (PciIoDevice, *Command);\r
-  PCI_READ_COMMAND_REGISTER (PciIoDevice, Command);\r
+  PCI_SET_COMMAND_REGISTER (PciIoDevice, CommandValue);\r
+  PCI_READ_COMMAND_REGISTER (PciIoDevice, &CommandValue);\r
 \r
+  *Command = *Command & CommandValue;\r
   //\r
   // Write back the original value\r
   //\r