Re: [PATCH 1/3] ArmPlatformPkg: Fix PL011 FIFO size test

[Leif Lindholm <leif.lindholm@linaro.org>]

Apologies for delay, now catching up post plugfest and Linaro Connect.

On Wed, Sep 21, 2016 at 09:33:13PM +0100, evan.lloyd@arm.com wrote:
> From: Evan Lloyd <evan.lloyd@arm.com>
> 
> This change updates PL011UartInitializePort to compare ReceiveFifoDepth
> with the correct hardware FIFO size instead of the constant 32 used
> previously.
> This corrects a minor bug where a request for a fifo size > 15 and < 32
> would not have been honoured on a system with a 16 byte FIFO.

Whoops.
Well, even without the bug, the below is an improvement in readability.

> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>
> Signed-off-by: Evan Lloyd <evan.lloyd@arm.com>
> ---
>  ArmPlatformPkg/Drivers/PL011Uart/PL011Uart.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/ArmPlatformPkg/Drivers/PL011Uart/PL011Uart.c b/ArmPlatformPkg/Drivers/PL011Uart/PL011Uart.c
> index 3748972acbfc80f1077b9b928756a72cc77b5c75..b3ea138bf60b93a1000dd29aedaad206f2d15f2b 100644
> --- a/ArmPlatformPkg/Drivers/PL011Uart/PL011Uart.c
> +++ b/ArmPlatformPkg/Drivers/PL011Uart/PL011Uart.c
> @@ -79,17 +79,18 @@ PL011UartInitializePort (
>    UINT32      Divisor;
>    UINT32      Integer;
>    UINT32      Fractional;
> +  UINT32      HardwareFifoDepth;
>  
> +  HardwareFifoDepth = (PL011_UARTPID2_VER (MmioRead32 (UartBase + UARTPID2)) \
> +                       > PL011_VER_R1P4) \
> +                      ? 32 : 16 ;

I may drop that space before ';' before committing, but apart from
that:
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>

>    // The PL011 supports a buffer of 1, 16 or 32 chars. Therefore we can accept
>    // 1 char buffer as the minimum FIFO size. Because everything can be rounded
>    // down, there is no maximum FIFO size.
> -  if ((*ReceiveFifoDepth == 0) || (*ReceiveFifoDepth >= 32)) {
> +  if ((*ReceiveFifoDepth == 0) || (*ReceiveFifoDepth >= HardwareFifoDepth)) {
>      // Enable FIFO
>      LineControl = PL011_UARTLCR_H_FEN;
> -    if (PL011_UARTPID2_VER (MmioRead32 (UartBase + UARTPID2)) > PL011_VER_R1P4)
> -      *ReceiveFifoDepth = 32;
> -    else
> -      *ReceiveFifoDepth = 16;
> +    *ReceiveFifoDepth = HardwareFifoDepth;
>    } else {
>      // Disable FIFO
>      LineControl = 0;
> -- 
> Guid("CE165669-3EF3-493F-B85D-6190EE5B9759")
>