Re: [PATCH 1/1] ArmVirtPkg/FdtPL011SerialPortLib: call PL011UartLib in all SerialPortLib APIs

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

On 16 August 2017 at 13:10, Laszlo Ersek <lersek@redhat.com> wrote:
> With the SerialDxe change in commit 4cf3f37c87ba ("MdeModulePkg SerialDxe:
> Process timeout consistently in SerialRead", 2017-07-18), setting
> EFI_SERIAL_INPUT_BUFFER_EMPTY in the "Control" output parameter, in the
> GetControl() SerialPortLib function, is no longer a "small optimization".
> Namely, due to the SerialDxe change, the GetOneKeyFromSerial() call in
> TerminalDxe's TerminalConInTimerHandler() can take very long if the input
> queue is empty, even if GetOneKeyFromSerial()'s return value causes the
> loop to be exited right after, in the first iteration.
>
> This issue causes a boot hang in ArmVirtQemu: with the input queue empty,
> TerminalConInTimerHandler() takes so long to return that, by the time it
> returns, there's another execution queued already (due to the associated
> timer event being signaled meanwhile). The boot process is stuck in the
> timer event handler.
>
> Therefore even the first GetOneKeyFromSerial() iteration must be prevented
> in TerminalConInTimerHandler() if the input queue is empty, and that
> requires implementing GetControl() for real.
>
> Implement the SetAttributes(), SetControl() and GetControl() APIs (of
> SerialPortExtLib origin) in FdtPL011SerialPortLib with calls to matching
> PL011UartLib functions. This follows the example of
> "ArmPlatformPkg/Library/PL011SerialPortLib" and also matches Star's
> original idea under [1].
>
> The patch can be considered a continuation of commit ad7f6bc2e116
> ("ArmVirtPkg: Use SerialDxe in MdeModulePkg instead of EmbeddedPkg",
> 2015-11-26), based on the mailing list threads [1] [2] [3].
>
> [1] http://mid.mail-archive.com/1447752930-32880-12-git-send-email-star.zeng@intel.com
> [2] http://mid.mail-archive.com/1448243067-1880-12-git-send-email-star.zeng@intel.com
> [3] http://mid.mail-archive.com/b748580c-cb51-32c9-acf9-780841ef15da@redhat.com
>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Brijesh Singh <brijesh.singh@amd.com>
> Cc: Heyi Guo <guoheyi@huawei.com>
> Cc: Star Zeng <star.zeng@intel.com>
> Originally-suggested-by: Star Zeng <star.zeng@intel.com>
> Reported-by: Brijesh Singh <brijesh.singh@amd.com>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Laszlo Ersek <lersek@redhat.com>

Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Thanks Laszlo!

> ---
>  ArmVirtPkg/Library/FdtPL011SerialPortLib/FdtPL011SerialPortLib.c | 38 ++++++++++++++++++--
>  1 file changed, 35 insertions(+), 3 deletions(-)
>
> diff --git a/ArmVirtPkg/Library/FdtPL011SerialPortLib/FdtPL011SerialPortLib.c b/ArmVirtPkg/Library/FdtPL011SerialPortLib/FdtPL011SerialPortLib.c
> index 48a0530dcc2f..05d3547fda91 100644
> --- a/ArmVirtPkg/Library/FdtPL011SerialPortLib/FdtPL011SerialPortLib.c
> +++ b/ArmVirtPkg/Library/FdtPL011SerialPortLib/FdtPL011SerialPortLib.c
> @@ -200,7 +200,23 @@ SerialPortSetAttributes (
>    IN OUT EFI_STOP_BITS_TYPE *StopBits
>    )
>  {
> -  return RETURN_UNSUPPORTED;
> +  RETURN_STATUS Status;
> +
> +  if (mSerialBaseAddress == 0) {
> +    Status = RETURN_UNSUPPORTED;
> +  } else {
> +    Status = PL011UartInitializePort (
> +               mSerialBaseAddress,
> +               FixedPcdGet32 (PL011UartClkInHz),
> +               BaudRate,
> +               ReceiveFifoDepth,
> +               Parity,
> +               DataBits,
> +               StopBits
> +               );
> +  }
> +
> +  return Status;
>  }
>
>  /**
> @@ -219,7 +235,15 @@ SerialPortSetControl (
>    IN UINT32 Control
>    )
>  {
> -  return RETURN_UNSUPPORTED;
> +  RETURN_STATUS Status;
> +
> +  if (mSerialBaseAddress == 0) {
> +    Status = RETURN_UNSUPPORTED;
> +  } else {
> +    Status = PL011UartSetControl (mSerialBaseAddress, Control);
> +  }
> +
> +  return Status;
>  }
>
>  /**
> @@ -238,6 +262,14 @@ SerialPortGetControl (
>    OUT UINT32 *Control
>    )
>  {
> -  return RETURN_UNSUPPORTED;
> +  RETURN_STATUS Status;
> +
> +  if (mSerialBaseAddress == 0) {
> +    Status = RETURN_UNSUPPORTED;
> +  } else {
> +    Status = PL011UartGetControl (mSerialBaseAddress, Control);
> +  }
> +
> +  return Status;
>  }
>
> --
> 2.14.1.3.gb7cf6e02401b
>
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