Re: [edk2-devel] [PATCH v2 1/5] Platform/RaspberryPi/DualSerialPortLib: Always configure the pl011

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

On Wed, 17 Jan 2024 at 22:36, Jeremy Linton <jeremy.linton@arm.com> wrote:
>
> The rpi's config.txt controls which uart (pl011, or miniuart) is
> selected as the console. TFA and edk2 follow its lead, but if the
> miniuart is selected as the primary and the machine is booted in ACPI
> mode the baud/etc is never configured for the pl011. The linux kernel
> won't reconfigure it either as its listed as a "SBSA" uart, so it
> simply won't work.
>
> This re-enables BT on the pl011 in ACPI mode, and it somewhat starts
> to work again.
>
> Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
> ---
>  .../DualSerialPortLib/DualSerialPortLib.c     | 44 ++++++++++++-------
>  1 file changed, 29 insertions(+), 15 deletions(-)
>
> diff --git a/Platform/RaspberryPi/Library/DualSerialPortLib/DualSerialPortLib.c b/Platform/RaspberryPi/Library/DualSerialPortLib/DualSerialPortLib.c
> index d2f983bf0a..09d3e33c00 100644
> --- a/Platform/RaspberryPi/Library/DualSerialPortLib/DualSerialPortLib.c
> +++ b/Platform/RaspberryPi/Library/DualSerialPortLib/DualSerialPortLib.c
> @@ -76,6 +76,8 @@ SerialPortInitialize (
>    EFI_PARITY_TYPE     Parity;
>    UINT8               DataBits;
>    EFI_STOP_BITS_TYPE  StopBits;
> +  RETURN_STATUS       Ret;
> +  UINTN               Timeout;
>
>    //
>    // First thing we need to do is determine which of PL011 or miniUART is selected
> @@ -85,23 +87,34 @@ SerialPortInitialize (
>      UsePl011UartSet = TRUE;
>    }
>
> -  if (UsePl011Uart) {
> -    BaudRate = FixedPcdGet64 (PcdUartDefaultBaudRate);
> +  // always init the pl011 on the RPi4, linux expects a SBSA uart to be at 115200
> +  // this means we need to set the baud/etc even if we aren't using it as a console
> +  if ((UsePl011Uart) || (RPI_MODEL == 4)) {
>      ReceiveFifoDepth = 0;         // Use default FIFO depth
> +    if (!UsePl011Uart)
> +    {
> +      BaudRate = 115200;
> +    }
> +    else
> +    {
> +      BaudRate = FixedPcdGet64 (PcdUartDefaultBaudRate);
> +    }
>      Parity = (EFI_PARITY_TYPE)FixedPcdGet8 (PcdUartDefaultParity);
>      DataBits = FixedPcdGet8 (PcdUartDefaultDataBits);
>      StopBits = (EFI_STOP_BITS_TYPE) FixedPcdGet8 (PcdUartDefaultStopBits);
>
> -    return PL011UartInitializePort (
> -             PL011_UART_REGISTER_BASE,
> -             PL011UartClockGetFreq(),
> -             &BaudRate,
> -             &ReceiveFifoDepth,
> -             &Parity,
> -             &DataBits,
> -             &StopBits
> -             );
> -  } else {
> +    Ret = PL011UartInitializePort (
> +           PL011_UART_REGISTER_BASE,
> +           PL011UartClockGetFreq(),
> +           &BaudRate,
> +           &ReceiveFifoDepth,
> +           &Parity,
> +           &DataBits,
> +           &StopBits
> +           );
> +  }
> +
> +  if (!UsePl011Uart) {
>      SerialRegisterBase = MINI_UART_REGISTER_BASE;
>      Divisor = SerialPortGetDivisor (PcdGet32 (PcdSerialBaudRate));
>
> @@ -127,7 +140,8 @@ SerialPortInitialize (
>      // Wait for the serial port to be ready.
>      // Verify that both the transmit FIFO and the shift register are empty.
>      //
> -    while ((SerialPortReadRegister (SerialRegisterBase, R_UART_LSR) & (B_UART_LSR_TEMT | B_UART_LSR_TXRDY)) != (B_UART_LSR_TEMT | B_UART_LSR_TXRDY));
> +    Timeout = 1000;
> +    while (((SerialPortReadRegister (SerialRegisterBase, R_UART_LSR) & (B_UART_LSR_TEMT | B_UART_LSR_TXRDY)) != (B_UART_LSR_TEMT | B_UART_LSR_TXRDY)) && (Timeout--));
>

Why is this necessary, and what does it have to do with the rest of the patch?

>      //
>      // Configure baud rate
> @@ -158,9 +172,9 @@ SerialPortInitialize (
>      // Put Modem Control Register(MCR) into its reset state of 0x00.
>      //
>      SerialPortWriteRegister (SerialRegisterBase, R_UART_MCR, 0x00);
> -
> -    return RETURN_SUCCESS;
> +    Ret = RETURN_SUCCESS;
>    }
> +  return Ret;
>  }
>
>  /**
> --
> 2.43.0
>


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