[U-Boot] [PATCH] arm: am33xx: Make pin multiplexing functions optional

[Tom Rini]

On Thu, Aug 31, 2017 at 03:16:17PM +0200, Felix Brack wrote:

> Boards using the single-register-pin-controller can  configure all
> pins by means of the device tree. This renders the implementation of
> the two functions set_uart_mux_conf and set_mux_conf_regs obsolete.
> Using the weak attribute for these two function declarations allows
> the omission of the respective definitions.
> 
> Signed-off-by: Felix Brack <fb at ltec.ch>
> ---
> 
>  arch/arm/include/asm/arch-am33xx/sys_proto.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/include/asm/arch-am33xx/sys_proto.h b/arch/arm/include/asm/arch-am33xx/sys_proto.h
> index 4e78aaf..e31c25c 100644
> --- a/arch/arm/include/asm/arch-am33xx/sys_proto.h
> +++ b/arch/arm/include/asm/arch-am33xx/sys_proto.h
> @@ -31,8 +31,8 @@ void enable_gpmc_cs_config(const u32 *gpmc_config, const struct gpmc_cs *cs, u32
>  			u32 size);
>  int omap_nand_switch_ecc(uint32_t, uint32_t);
>  
> -void set_uart_mux_conf(void);
> -void set_mux_conf_regs(void);
> +__weak void set_uart_mux_conf(void);
> +__weak void set_mux_conf_regs(void);
>  void sdram_init(void);
>  u32 wait_on_value(u32, u32, void *, u32);
>  #ifdef CONFIG_NOR_BOOT

This seems wrong in a few ways.  First, this (and the matching ones for
omap3, etc) should be full of externs instead and in that case __weak
makes no sense.  Then, on the technical side, what you're describing
isn't quite true in that you're likely relying on having the ROM to have
setup the 'normal' UART still for you, as it so often does, I believe.
Or in the case I'm wrong, then yes, you do get UART to work once we have
parsed the DT, but the "usual" case is that we want UART and thus
printf/etc to be available asap in case of errors, so it's still not a
recommended way to go.  Thanks!

-- 
Tom
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