Re: [Xen-devel] [PATCH V4 5/5] xen/arm: Add early printk support for SCIFA compatible UARTs

[Julien Grall <julien.grall@xxxxxxx>]

Hi Oleksandr,

On 17/04/2019 15:59, Oleksandr Tyshchenko wrote:
> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
>
> This patch makes possible to use existing early prink code
> for Renesas "Stout" board based on R-Car H2 SoC (SCIFA).
>
> The "EARLY_PRINTK_VERSION" for that board should be 'A':
> CONFIG_EARLY_PRINTK=scif,0xe6c40000,A
>
> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> CC: Julien Grall <julien.grall@xxxxxxx>
>
> ---
>      Changes in v3:
>          - It was decided not to introduce new debug-scifa.inc
>            for handling SCIFA interface, but to extend existing
>            debug-scif.inc for handling both interfaces.
>            This patch is a result of splitting an initial patch
>            "xen/arm: Add SCIFA UART support for early printk"
>            and only adds a support.
>
>      Changes in v4:
>          - Drop SCIF(A) from comments
> ---
>   xen/arch/arm/arm32/debug-scif.inc | 9 ++++++---
>   1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/xen/arch/arm/arm32/debug-scif.inc 
> b/xen/arch/arm/arm32/debug-scif.inc
> index a8d2eae..3f01c90 100644
> --- a/xen/arch/arm/arm32/debug-scif.inc
> +++ b/xen/arch/arm/arm32/debug-scif.inc
> @@ -1,7 +1,7 @@
>   /*
>    * xen/arch/arm/arm32/debug-scif.inc
>    *
> - * SCIF specific debug code
> + * SCIF(A) specific debug code
>    *
>    * Oleksandr Tyshchenko <oleksandr.tyshchenko@xxxxxxxxxxxxxxx>
>    * Copyright (C) 2014, Globallogic.
> @@ -22,10 +22,13 @@
>   #ifdef EARLY_PRINTK_VERSION_NONE
>   #define STATUS_REG    SCIF_SCFSR
>   #define TX_FIFO_REG   SCIF_SCFTDR
> +#elif EARLY_PRINTK_VERSION_A
> +#define STATUS_REG    SCIFA_SCASSR
> +#define TX_FIFO_REG   SCIFA_SCAFTDR
>   #endif
>   
>   /*
> - * SCIF UART wait UART to be ready to transmit
> + * Wait UART to be ready to transmit
This change and ...

>    * rb: register which contains the UART base address
>    * rc: scratch register
>    */
> @@ -37,7 +40,7 @@
>   .endm
>   
>   /*
> - * SCIF UART transmit character
> + * UART transmit character
... this one look like more a change for the previous than this one.

>    * rb: register which contains the UART base address
>    * rt: register which contains the character to transmit
>    */
Cheers,

--
Julien Grall

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