Re: [edk2-platforms][PATCH 1/1] Platform/RaspberryPi: Fix mini UART baud divisor calculation

["Ard Biesheuvel" <ardb@kernel.org>]

On Fri, 2 Apr 2021 at 19:52, Mario Bălănică <mariobalanica02@gmail.com> wrote:
>
> The baud rate divisor calculation for mini UART on BCM2711 is the same
> as on older models since this commit:
> https://github.com/raspberrypi/firmware/commit/1e5456a
>
> Signed-off-by: Mario Bălănică <mariobalanica02@gmail.com>

Doesn't this make the new build incompatible with the old firmware? Is
there a way to support both?


> ---
>  Platform/RaspberryPi/Library/DualSerialPortLib/DualSerialPortLib.c   | 15 +++------------
>  Platform/RaspberryPi/Library/PlatformLib/AArch64/RaspberryPiHelper.S |  4 ----
>  Platform/RaspberryPi/RPi4/RPi4.dsc                                   |  6 ++++--
>  3 files changed, 7 insertions(+), 18 deletions(-)
>
> diff --git a/Platform/RaspberryPi/Library/DualSerialPortLib/DualSerialPortLib.c b/Platform/RaspberryPi/Library/DualSerialPortLib/DualSerialPortLib.c
> index 5e83bbf022eb..d2f983bf0a9f 100644
> --- a/Platform/RaspberryPi/Library/DualSerialPortLib/DualSerialPortLib.c
> +++ b/Platform/RaspberryPi/Library/DualSerialPortLib/DualSerialPortLib.c
> @@ -34,25 +34,16 @@ SerialPortGetDivisor (
>    UINT32  SerialBaudRate
>  )
>  {
> -  UINT64              BaseClockRate;
> +  UINT32              BaseClockRate;
>    UINT32              Divisor;
>
> -  //
> -  // On the Raspberry Pi, the clock to use for the 16650-compatible UART
> -  // is the base clock divided by the 12.12 fixed point VPU clock divisor.
> -  //
> -  BaseClockRate = (UINT64)PcdGet32 (PcdSerialClockRate);
> -#if (RPI_MODEL == 4)
> -  Divisor = MmioRead32(BCM2836_CM_BASE + BCM2836_CM_VPU_CLOCK_DIVISOR) & 0xFFFFFF;
> -  if (Divisor != 0)
> -    BaseClockRate = (BaseClockRate << 12) / Divisor;
> -#endif
> +  BaseClockRate = PcdGet32 (PcdSerialClockRate);
>
>    //
>    // As per the BCM2xxx datasheets:
>    // baudrate = system_clock_freq / (8 * (divisor + 1)).
>    //
> -  Divisor = (UINT32)BaseClockRate / (SerialBaudRate * 8);
> +  Divisor = BaseClockRate / (SerialBaudRate * 8);
>    if (Divisor != 0) {
>      Divisor--;
>    }
> diff --git a/Platform/RaspberryPi/Library/PlatformLib/AArch64/RaspberryPiHelper.S b/Platform/RaspberryPi/Library/PlatformLib/AArch64/RaspberryPiHelper.S
> index 58351e4fb8cc..7008aaf8aa4c 100644
> --- a/Platform/RaspberryPi/Library/PlatformLib/AArch64/RaspberryPiHelper.S
> +++ b/Platform/RaspberryPi/Library/PlatformLib/AArch64/RaspberryPiHelper.S
> @@ -85,13 +85,11 @@ ASM_FUNC (ArmPlatformPeiBootAction)
>      adr     x2, mBoardRevision
>      str     w0, [x2]
>
> -#if (RPI_MODEL == 3)
>      run     .Lclkinfo_buffer
>
>      ldr     w0, .Lfrequency
>      adr     x2, _gPcd_BinaryPatch_PcdSerialClockRate
>      str     w0, [x2]
> -#endif
>
>      ret
>
> @@ -135,7 +133,6 @@ ASM_FUNC (ArmPlatformPeiBootAction)
>      .long   0                           // end tag
>      .set    .Lrevinfo_size, . - .Lrevinfo_buffer
>
> -#if (RPI_MODEL == 3)
>      .align  4
>  .Lclkinfo_buffer:
>      .long   .Lclkinfo_size
> @@ -148,7 +145,6 @@ ASM_FUNC (ArmPlatformPeiBootAction)
>      .long   0                           // frequency
>      .long   0                           // end tag
>      .set    .Lclkinfo_size, . - .Lclkinfo_buffer
> -#endif
>
>  //UINTN
>  //ArmPlatformGetPrimaryCoreMpId (
> diff --git a/Platform/RaspberryPi/RPi4/RPi4.dsc b/Platform/RaspberryPi/RPi4/RPi4.dsc
> index 2c05c31118d2..ff802d8347ea 100644
> --- a/Platform/RaspberryPi/RPi4/RPi4.dsc
> +++ b/Platform/RaspberryPi/RPi4/RPi4.dsc
> @@ -429,7 +429,6 @@ [PcdsFixedAtBuild.common]
>    gArmPlatformTokenSpaceGuid.PL011UartClkInHz|48000000
>    gEfiMdeModulePkgTokenSpaceGuid.PcdSerialUseMmio|TRUE
>    gEfiMdeModulePkgTokenSpaceGuid.PcdSerialRegisterStride|4
> -  gEfiMdeModulePkgTokenSpaceGuid.PcdSerialClockRate|1000000000
>    gEfiMdeModulePkgTokenSpaceGuid.PcdSerialFifoControl|0x27
>    gEfiMdeModulePkgTokenSpaceGuid.PcdSerialExtendedTxFifoSize|8
>    gEfiMdePkgTokenSpaceGuid.PcdUartDefaultBaudRate|115200
> @@ -465,6 +464,9 @@ [PcdsFixedAtBuild.common]
>    gEfiMdeModulePkgTokenSpaceGuid.PcdFirmwareVendor|L"EDK2"
>    gEfiMdeModulePkgTokenSpaceGuid.PcdSetNxForStack|TRUE
>
> +[PcdsPatchableInModule]
> +  gEfiMdeModulePkgTokenSpaceGuid.PcdSerialClockRate|500000000
> +
>  [PcdsDynamicHii.common.DEFAULT]
>
>    #
> @@ -621,7 +623,7 @@ [Components.common]
>    MdeModulePkg/Universal/Console/TerminalDxe/TerminalDxe.inf
>    MdeModulePkg/Universal/SerialDxe/SerialDxe.inf {
>      <LibraryClasses>
> -      SerialPortLib|Platform/RaspberryPi/Library/DualSerialPortLib/DualSerialPortLib.inf
> +      SerialPortLib|Platform/RaspberryPi/Library/DualSerialPortLib/DualSerialPortDxeLib.inf
>    }
>    Platform/RaspberryPi/Drivers/DisplayDxe/DisplayDxe.inf
>    EmbeddedPkg/Drivers/ConsolePrefDxe/ConsolePrefDxe.inf
> --
> 2.29.2.windows.2
>