Re: [Xen-devel] [PATCH v4] xen/arm: Add Amlogic Meson SoCs earlyprintk support

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

On 14/04/2019 18:50, Amit Singh Tomar wrote:
> This patch adds earlyprintk support for Amlogic Meson SoC based
> boards.
>
> ATF[1] and U-boot[2] already initialize the UART for us. So no need to do it 
> again.
>
> Tested With:
>   http://wiki.friendlyarm.com/wiki/index.php/NanoPi_K2
>
> [1]: 
> https://github.com/ARM-software/arm-trusted-firmware/blob/master/drivers/meson/console/aarch64/meson_console.S#L92
> [2]: 
> https://github.com/u-boot/u-boot/blob/master/drivers/serial/serial_meson.c#L44
>
> Signed-off-by: Amit Singh Tomar <amittomer25@xxxxxxxxx>
Acked-by: Julien Grall <julien.grall@xxxxxxx>

I have pushed to my branch next-4.13 for now. It will be merged once the commit 
moratorium is lifted.
Cheers,

> ---
> Changes since v3:
>      
>          * Change the commit message to include firmware names.
> Changes since v2:
>
>          * Added the commit message that talks about
>            uart initialization.
>
>          * Added dummy early_uart_init function.
>
> Changes since v1:
>
>          * Fixed coding style issue.
>          * Undone changes in early-printk.txt.
>
> Changes since RFC:
>
>          * Replaced LDRH with LDR, with this there
>            is no scattered output on console now.
>          * Used tbnz instead of tst and b.ne.
>          * Used AML_ prefix against register names.
>
> ---
>   xen/arch/arm/arm64/debug-meson.inc | 55 ++++++++++++++++++++++++++++++++++++++
>   1 file changed, 55 insertions(+)
>   create mode 100644 xen/arch/arm/arm64/debug-meson.inc
>
> diff --git a/xen/arch/arm/arm64/debug-meson.inc 
> b/xen/arch/arm/arm64/debug-meson.inc
> new file mode 100644
> index 0000000..e1a8fa8
> --- /dev/null
> +++ b/xen/arch/arm/arm64/debug-meson.inc
> @@ -0,0 +1,55 @@
> +/*
> + * xen/arch/arm/arm64/debug-meson.inc
> + *
> + * MESON specific debug code.
> + *
> + * Copyright (c) 2019, Amit Singh Tomar <amittomer25@xxxxxxxxx>.
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms and conditions of the GNU General Public
> + * License, version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public
> + * License along with this program; If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#define AML_UART_WFIFO_REG      0x00
> +#define AML_UART_STATUS_REG     0x0c
> +
> +#define AML_UART_TX_FIFO_FULL   21
> +
> +.macro early_uart_init xb, c
> +/* Uart has already been initialized by Firmware, for instance by TF-A */
> +.endm
> +
> +/*
> + * MESON UART wait UART to be ready to transmit
> + * xb: register which contains the UART base address
> + * c: scratch register
> + */
> +.macro early_uart_ready xb c
> +1:
> +        ldr     w\c, [\xb, #AML_UART_STATUS_REG]        /* status register */
> +        tbnz    w\c, #AML_UART_TX_FIFO_FULL, 1b         /* Check TXFIFO FULL 
> bit */
> +.endm
> +
> +/*
> + * MESON UART transmit character
> + * xb: register which contains the UART base address
> + * wt: register which contains the character to transmit
> + */
> +.macro early_uart_transmit xb wt
> +        str    \wt, [\xb, #AML_UART_WFIFO_REG]
> +.endm
> +
> +/*
> + * Local variables:
> + * mode: ASM
> + * indent-tabs-mode: nil
> + * End:
> + */
--
Julien Grall

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