[PATCH edk2-platforms 4/5] Platform/RaspberryPi3: query firmware for 16550 input clock at boot

["Ard Biesheuvel" <ard.biesheuvel@arm.com>]

Query the firmware for the clock rate that is used to drive the
16550 baud clock, so that we can program the correct baud rate.

Co-authored-by: Pete Batard <pete@akeo.ie>
Co-authored-by: Andrei Warkentin <andrey.warkentin@gmail.com>
Co-authored-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
Signed-off-by: Pete Batard <pete@akeo.ie>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
---
 Platform/RaspberryPi/Library/PlatformLib/AArch64/RaspberryPiHelper.S | 25 +++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/Platform/RaspberryPi/Library/PlatformLib/AArch64/RaspberryPiHelper.S b/Platform/RaspberryPi/Library/PlatformLib/AArch64/RaspberryPiHelper.S
index 91dfe1bb981e..35580e4ed73a 100644
--- a/Platform/RaspberryPi/Library/PlatformLib/AArch64/RaspberryPiHelper.S
+++ b/Platform/RaspberryPi/Library/PlatformLib/AArch64/RaspberryPiHelper.S
@@ -3,7 +3,7 @@
  *  Copyright (c) 2020, Andrei Warkentin <andrey.warkentin@gmail.com>
  *  Copyright (c) 2019-2020, Pete Batard <pete@akeo.ie>
  *  Copyright (c) 2016, Linaro Limited. All rights reserved.
- *  Copyright (c) 2011-2013, ARM Limited. All rights reserved.
+ *  Copyright (c) 2011-2020, ARM Limited. All rights reserved.
  *
  *  SPDX-License-Identifier: BSD-2-Clause-Patent
  *
@@ -85,6 +85,14 @@ ASM_FUNC (ArmPlatformPeiBootAction)
     adr     x2, mBoardRevision
     str     w0, [x2]
 
+#if (RPI_MODEL == 3)
+    run     .Lclkinfo_buffer
+
+    ldr     w0, .Lfrequency
+    adrp    x2, _gPcd_BinaryPatch_PcdSerialClockRate
+    str     w0, [x2, :lo12:_gPcd_BinaryPatch_PcdSerialClockRate]
+#endif
+
     ret
 
     .align  4
@@ -127,6 +135,21 @@ ASM_FUNC (ArmPlatformPeiBootAction)
     .long   0                           // end tag
     .set    .Lrevinfo_size, . - .Lrevinfo_buffer
 
+#if (RPI_MODEL == 3)
+    .align  4
+.Lclkinfo_buffer:
+    .long   .Lclkinfo_size
+    .long   0x0
+    .long   RPI_MBOX_GET_CLOCK_RATE
+    .long   8                           // buf size
+    .long   4                           // input len
+    .long   4                           // clock id: 0x04 = Core/VPU
+.Lfrequency:
+    .long   0                           // frequency
+    .long   0                           // end tag
+    .set    .Lclkinfo_size, . - .Lclkinfo_buffer
+#endif
+
 //UINTN
 //ArmPlatformGetPrimaryCoreMpId (
 //  VOID
-- 
2.17.1