[RFC] ARM: OMAP: debug_ll: Add support for PBL console

[Sascha Hauer]

On Thu, May 05, 2022 at 12:42:54PM +0300, Alexander Shiyan wrote:
> Signed-off-by: Alexander Shiyan <eagle.alexander923 at gmail.com>
> ---
>  arch/arm/boards/myirtech-x335x/lowlevel.c  | 10 ++++------
>  arch/arm/mach-omap/include/mach/debug_ll.h | 20 ++++++++++++++------
>  2 files changed, 18 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/arm/boards/myirtech-x335x/lowlevel.c b/arch/arm/boards/myirtech-x335x/lowlevel.c
> index 1a883da203..f9f3ec4ddf 100644
> --- a/arch/arm/boards/myirtech-x335x/lowlevel.c
> +++ b/arch/arm/boards/myirtech-x335x/lowlevel.c
> @@ -95,12 +95,10 @@ ENTRY_FUNCTION(start_am33xx_myirtech_sram, bootinfo, r1, r2)
>  		am335x_sdram_init(0x18b, &ddr3_cmd_ctrl, &ddr3_regs, &ddr3_data);
>  	}
>  
> -	if (IS_ENABLED(CONFIG_DEBUG_LL)) {
> -		am33xx_uart_soft_reset(IOMEM(AM33XX_UART0_BASE));
> -		am33xx_enable_uart0_pin_mux();
> -		omap_uart_lowlevel_init(IOMEM(AM33XX_UART0_BASE));
> -		putc_ll('>');
> -	}
> +	am33xx_uart_soft_reset(IOMEM(AM33XX_UART0_BASE));
> +	am33xx_enable_uart0_pin_mux();
> +	omap_uart_lowlevel_init(IOMEM(AM33XX_UART0_BASE));
> +	pr_debug("MYIR MYC-AM335X\n");
>  
>  	am335x_barebox_entry(fdt);
>  }
> diff --git a/arch/arm/mach-omap/include/mach/debug_ll.h b/arch/arm/mach-omap/include/mach/debug_ll.h
> index 25ddd485be..018171d112 100644
> --- a/arch/arm/mach-omap/include/mach/debug_ll.h
> +++ b/arch/arm/mach-omap/include/mach/debug_ll.h
> @@ -17,6 +17,7 @@
>  #ifndef __MACH_DEBUG_LL_H__
>  #define   __MACH_DEBUG_LL_H__
>  
> +#include <console.h>
>  #include <io.h>
>  #include <mach/omap3-silicon.h>
>  #include <mach/omap4-silicon.h>
> @@ -34,6 +35,16 @@
>  #define MCR		(4 << 2)
>  #define MDR		(8 << 2)
>  
> +static inline void omap_uart_putc(void *base, int c)
> +{
> +	/* Wait until there is space in the FIFO */
> +	while ((readb(base + LSR) & LSR_THRE) == 0);
> +	/* Send the character */
> +	writeb(c, base + THR);
> +	/* Wait to make sure it hits the line, in case we die too soon. */
> +	while ((readb(base + LSR) & LSR_THRE) == 0);
> +}
> +
>  static inline void omap_uart_lowlevel_init(void __iomem *base)
>  {
>  	writeb(0x00, base + LCR);
> @@ -46,6 +57,8 @@ static inline void omap_uart_lowlevel_init(void __iomem *base)
>  	writeb(0x03, base + MCR);
>  	writeb(0x07, base + FCR);
>  	writeb(0x00, base + MDR);
> +
> +	pbl_set_putc(omap_uart_putc, base);

This should be called by the board code. pbl_set_putc() will only work
when we a running in a full C environment, i.e. we are running at the
address we are linked at. omap_uart_lowlevel_init() doesn't have this
constraint and could be used earlier.

Otherwise looks good.

Sascha


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