[U-Boot] [PATCH v2 4/9] arm: add _thumb1_case_uqi to libgcc

[Stephen Warren]

On 08/01/2012 02:32 PM, Allen Martin wrote:
> Add function required by some thumb switch statements

> diff --git a/arch/arm/lib/_thumb1_case_uqi.S b/arch/arm/lib/_thumb1_case_uqi.S

> +	.force_thumb

I believe that line should be removed.

The issue here is that when gcc emits Thumb code to call this function,
it actually emits:

>   108af8:       f000 f94a       bl      108d90 <____gnu_thumb1_case_uqi_from_thumb>

which is implemented as:

> 00108d90 <____gnu_thumb1_case_uqi_from_thumb>:
>   108d90:       4778            bx      pc
>   108d92:       46c0            nop                     ; (mov r8, r8)
>   108d94:       eafffde1        b       108520 <__gnu_thumb1_case_uqi>

i.e. it switches to ARM mode then jumps to that function. Hence,
__gnu_thumb1_case_uqi must be compiled as ARM, not as Thumb.

(renaming the function to ____gnu_thumb1_case_uqi_from_thumb in the hope
it'll be called directly instead of going through a stub doesn't seem to
work)

If I make that change, then this patch series starts working on
Whistler, which for reference, uses UARTA, so triggers funcmux.c's
funcmux_select() to enter case PERIPH_ID_UART1, which then uses
____gnu_thumb1_case_uqi_from_thumb to perform the nested switch (config).