linux-kernel - Re: [PATCH] ARM: davinci: only use NVMEM when available

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Message-ID: <56EA8654.5070100@linaro.org>
Date:	Thu, 17 Mar 2016 10:26:28 +0000
From:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Sekhar Nori <nsekhar@...com>, Kevin Hilman <khilman@...nel.org>,
	Andrew Lunn <andrew@...n.ch>, Wolfram Sang <wsa@...-dreams.de>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: davinci: only use NVMEM when available

Thanks for the patch,

On 15/03/16 21:34, Arnd Bergmann wrote:
> The davinci platform contains code that calls into the nvmem
> subsystem, but that might be a loadable module, causing a
> link error:
>
> arch/arm/mach-davinci/built-in.o: In function `davinci_get_mac_addr':
> :(.text+0x1088): undefined reference to `nvmem_device_read'
> arch/arm/mach-davinci/built-in.o: In function `read_factory_config':
> :(.text+0x214c): undefined reference to `nvmem_device_read'
>
This fix does not look correct to me.

IMO, This is a issue with incorrect dependencies in the Kconfig, we 
should not attempt to fix it in the code, rather fix the kconfig 
dependencies in the mach-davnici or the EEPROM_AT24 kconfig itself. one 
of them should select the NVMEM.


thanks,
srini



> Also, when NVMEM is completely disabled, the functions fail with
> nonobvious error messages.
>
> This ensures we only call the API functions when the code is actually
> reachable from the board file, and otherwise prints a unique log
> message.
>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> Fixes: bec3c11bad0e ("misc: at24: replace memory_accessor with nvmem_device_read")

> ---
>
> Hi Greg,
>
> The commit that introduced this is currently in the char-misc tree,
> please apply this fixup on top if you haven't already sent it to Linus.
>
>   arch/arm/mach-davinci/board-mityomapl138.c | 5 +++++
>   arch/arm/mach-davinci/common.c             | 5 +++++
>   2 files changed, 10 insertions(+)
>
> diff --git a/arch/arm/mach-davinci/board-mityomapl138.c b/arch/arm/mach-davinci/board-mityomapl138.c
> index d97c588550ad..bc4e63fa9808 100644
> --- a/arch/arm/mach-davinci/board-mityomapl138.c
> +++ b/arch/arm/mach-davinci/board-mityomapl138.c
> @@ -121,6 +121,11 @@ static void read_factory_config(struct nvmem_device *nvmem, void *context)
>   	const char *partnum = NULL;
>   	struct davinci_soc_info *soc_info = &davinci_soc_info;
>
> +	if (!IS_BUILTIN(CONFIG_NVMEM)) {
> +		pr_warn("Factory Config not available without CONFIG_NVMEM\n");
> +		goto bad_config;
> +	}
> +
>   	ret = nvmem_device_read(nvmem, 0, sizeof(factory_config),
>   				&factory_config);
>   	if (ret != sizeof(struct factory_config)) {
> diff --git a/arch/arm/mach-davinci/common.c b/arch/arm/mach-davinci/common.c
> index f55ef2ef2f92..742133b7266a 100644
> --- a/arch/arm/mach-davinci/common.c
> +++ b/arch/arm/mach-davinci/common.c
> @@ -33,6 +33,11 @@ void davinci_get_mac_addr(struct nvmem_device *nvmem, void *context)
>   	char *mac_addr = davinci_soc_info.emac_pdata->mac_addr;
>   	off_t offset = (off_t)context;
>
> +	if (!IS_BUILTIN(CONFIG_NVMEM)) {
> +		pr_warn("Cannot read MAC addr from EEPROM without CONFIG_NVMEM\n");
> +		return;
> +	}
> +
>   	/* Read MAC addr from EEPROM */
>   	if (nvmem_device_read(nvmem, offset, ETH_ALEN, mac_addr) == ETH_ALEN)
>   		pr_info("Read MAC addr from EEPROM: %pM\n", mac_addr);
>