linux-kernel - Re: [PATCH 1/3] ARM: EXYNOS: uncompress - print debug messages if DEBUG

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Message-ID: <20130601035929.GA3868@quad.lixom.net>
Date:	Fri, 31 May 2013 20:59:29 -0700
From:	Olof Johansson <olof@...om.net>
To:	Tushar Behera <tushar.behera@...aro.org>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, arnd@...db.de,
	kgene.kim@...sung.com, patches@...aro.org
Subject: Re: [PATCH 1/3] ARM: EXYNOS: uncompress - print debug messages if
 DEBUG_LL is defined

On Fri, May 31, 2013 at 05:19:02PM +0530, Tushar Behera wrote:
> Printing low-level debug messages make an assumption that the specified
> UART port has been preconfigured by the bootloader. Incorrectly
> specified UART port results in system getting stalled while printing the
> message "Uncompressing Linux... done, booting the kernel"
> 
> This UART port number is specified through S3C_LOWLEVEL_UART_PORT. Since
> the UART port might different for different board, it is not possible to
> specify it correctly for every board that use a common defconfig file.
> 
> Calling this print subroutine only when DEBUG_LL fixes the problem. By
> disabling DEBUG_LL in default config file, we would be able to boot
> multiple boards with different default UART ports.
> 
> With this current approach, we miss the print "Uncompressing Linux...
> done, booting the kernel." when DEBUG_LL is not defined.
> 
> Signed-off-by: Tushar Behera <tushar.behera@...aro.org>
> ---
>  arch/arm/mach-exynos/include/mach/uncompress.h  |   11 ++++++++---
>  arch/arm/plat-samsung/include/plat/uncompress.h |   10 +++++++++-
>  2 files changed, 17 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm/mach-exynos/include/mach/uncompress.h b/arch/arm/mach-exynos/include/mach/uncompress.h
> index 2979995..730f69f 100644
> --- a/arch/arm/mach-exynos/include/mach/uncompress.h
> +++ b/arch/arm/mach-exynos/include/mach/uncompress.h
> @@ -37,11 +37,16 @@ static void arch_detect_cpu(void)
>  	chip_id >>= 20;
>  	chip_id &= 0xf;
>  
> +#ifdef CONFIG_DEBUG_LL
>  	if (chip_id == 0x5)
> -		uart_base = (volatile u8 *)EXYNOS5_PA_UART + (S3C_UART_OFFSET * CONFIG_S3C_LOWLEVEL_UART_PORT);
> +		uart_base = (volatile u8 *)EXYNOS5_PA_UART +
> +			(S3C_UART_OFFSET * CONFIG_S3C_LOWLEVEL_UART_PORT);
>  	else
> -		uart_base = (volatile u8 *)EXYNOS4_PA_UART + (S3C_UART_OFFSET * CONFIG_S3C_LOWLEVEL_UART_PORT);
> -
> +		uart_base = (volatile u8 *)EXYNOS4_PA_UART +
> +			(S3C_UART_OFFSET * CONFIG_S3C_LOWLEVEL_UART_PORT);
> +#else
> +	uart_base = NULL;
> +#endif

You can do:

	if (!config_enabled(CONFIG_DEBUG_LL))
		return;

Since uart_base will be set to 0 by being in BSS anyway.


-Olof
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