ArmVirtPkg: QemuFwCfgLib: read bytes from fw-cfg with DMA when available

The protocol is documented in "docs/specs/fw_cfg.txt" in the QEMU tree.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18545 6f19259b-4bc3-4df7-8a09-765794883524

2 files changed, 121 insertions, 7 deletions

diff --git a/ArmVirtPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c b/ArmVirtPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c
index c62eee3be8..303dc520c6 100644
--- a/ArmVirtPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c
+++ b/ArmVirtPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c
@@ -16,12 +16,58 @@
 

 #include <Library/BaseLib.h>

 #include <Library/BaseMemoryLib.h>

+#include <Library/DebugLib.h>

 #include <Library/IoLib.h>

 #include <Library/PcdLib.h>

 #include <Library/QemuFwCfgLib.h>

 

 STATIC UINTN mFwCfgSelectorAddress;

 STATIC UINTN mFwCfgDataAddress;

+STATIC UINTN mFwCfgDmaAddress;

+

+/**

+  Reads firmware configuration bytes into a buffer

+

+  @param[in] Size    Size in bytes to read

+  @param[in] Buffer  Buffer to store data into  (OPTIONAL if Size is 0)

+

+**/

+typedef

+VOID (EFIAPI READ_BYTES_FUNCTION) (

+  IN UINTN Size,

+  IN VOID  *Buffer OPTIONAL

+  );

+

+//

+// Forward declaration of the two implementations we have.

+//

+STATIC READ_BYTES_FUNCTION MmioReadBytes;

+STATIC READ_BYTES_FUNCTION DmaReadBytes;

+

+//

+// This points to the one we detect at runtime.

+//

+STATIC READ_BYTES_FUNCTION *InternalQemuFwCfgReadBytes = MmioReadBytes;

+

+//

+// Communication structure for DmaReadBytes(). All fields are encoded in big

+// endian.

+//

+#pragma pack (1)

+typedef struct {

+  UINT32 Control;

+  UINT32 Length;

+  UINT64 Address;

+} FW_CFG_DMA_ACCESS;

+#pragma pack ()

+

+//

+// Macros for the FW_CFG_DMA_ACCESS.Control bitmap (in native encoding).

+//

+#define FW_CFG_DMA_CTL_ERROR  BIT0

+#define FW_CFG_DMA_CTL_READ   BIT1

+#define FW_CFG_DMA_CTL_SKIP   BIT2

+#define FW_CFG_DMA_CTL_SELECT BIT3

 

 

 /**

@@ -77,7 +123,22 @@ QemuFwCfgInitialize (
 

     QemuFwCfgSelectItem (QemuFwCfgItemSignature);

     Signature = QemuFwCfgRead32 ();

-    if (Signature != SIGNATURE_32 ('Q', 'E', 'M', 'U')) {

+    if (Signature == SIGNATURE_32 ('Q', 'E', 'M', 'U')) {

+      //

+      // For DMA support, we require the DTB to advertise the register, and the

+      // feature bitmap (which we read without DMA) to confirm the feature.

+      //

+      if (PcdGet64 (PcdFwCfgDmaAddress) != 0) {

+        UINT32 Features;

+

+        QemuFwCfgSelectItem (QemuFwCfgItemInterfaceVersion);

+        Features = QemuFwCfgRead32 ();

+        if ((Features & BIT1) != 0) {

+          mFwCfgDmaAddress = PcdGet64 (PcdFwCfgDmaAddress);

+          InternalQemuFwCfgReadBytes = DmaReadBytes;

+        }

+      }

+    } else {

       mFwCfgSelectorAddress = 0;

       mFwCfgDataAddress     = 0;

     }

@@ -108,16 +169,12 @@ QemuFwCfgSelectItem (
 

 

 /**

-  Reads firmware configuration bytes into a buffer

-

-  @param[in] Size    Size in bytes to read

-  @param[in] Buffer  Buffer to store data into  (OPTIONAL if Size is 0)

-

+  Slow READ_BYTES_FUNCTION.

 **/

 STATIC

 VOID

 EFIAPI

-InternalQemuFwCfgReadBytes (

+MmioReadBytes (

   IN UINTN Size,

   IN VOID  *Buffer OPTIONAL

   )

@@ -163,6 +220,61 @@ InternalQemuFwCfgReadBytes (
 

 

 /**

+  Fast READ_BYTES_FUNCTION.

+**/

+STATIC

+VOID

+EFIAPI

+DmaReadBytes (

+  IN UINTN Size,

+  IN VOID  *Buffer OPTIONAL

+  )

+{

+  volatile FW_CFG_DMA_ACCESS Access;

+  UINT32                     Status;

+

+  if (Size == 0) {

+    return;

+  }

+

+  ASSERT (Size <= MAX_UINT32);

+

+  Access.Control = SwapBytes32 (FW_CFG_DMA_CTL_READ);

+  Access.Length  = SwapBytes32 ((UINT32)Size);

+  Access.Address = SwapBytes64 ((UINT64)(UINTN)Buffer);

+

+  //

+  // We shouldn't start the transfer before setting up Access.

+  //

+  MemoryFence ();

+

+  //

+  // This will fire off the transfer.

+  //

+#ifdef MDE_CPU_AARCH64

+  MmioWrite64 (mFwCfgDmaAddress, SwapBytes64 ((UINT64)&Access));

+#else

+  MmioWrite32 ((UINT32)(mFwCfgDmaAddress + 4), SwapBytes32 ((UINT32)&Access));

+#endif

+

+  //

+  // We shouldn't look at Access.Control before starting the transfer.

+  //

+  MemoryFence ();

+

+  do {

+    Status = SwapBytes32 (Access.Control);

+    ASSERT ((Status & FW_CFG_DMA_CTL_ERROR) == 0);

+  } while (Status != 0);

+

+  //

+  // The caller will want to access the transferred data.

+  //

+  MemoryFence ();

+}

+

+

+/**

   Reads firmware configuration bytes into a buffer

 

   If called multiple times, then the data read will continue at the offset of

diff --git a/ArmVirtPkg/Library/QemuFwCfgLib/QemuFwCfgLib.inf b/ArmVirtPkg/Library/QemuFwCfgLib/QemuFwCfgLib.inf
index 42f21f20c0..298aa6edfb 100644
--- a/ArmVirtPkg/Library/QemuFwCfgLib/QemuFwCfgLib.inf
+++ b/ArmVirtPkg/Library/QemuFwCfgLib/QemuFwCfgLib.inf
@@ -44,9 +44,11 @@
 [LibraryClasses]

   BaseLib

   BaseMemoryLib

+  DebugLib

   IoLib

   PcdLib

 

 [Pcd]

   gArmVirtTokenSpaceGuid.PcdFwCfgSelectorAddress

   gArmVirtTokenSpaceGuid.PcdFwCfgDataAddress

+  gArmVirtTokenSpaceGuid.PcdFwCfgDmaAddress