Re: [PATCH V4 22/23] platform/surface: Disable for RISC-V

[Jessica Clarke]

On 4 Apr 2023, at 19:20, Sunil V L <sunilvl@xxxxxxxxxxxxxxxx> wrote:
> 
> With CONFIG_ACPI enabled for RISC-V, this driver gets enabled
> in allmodconfig build. However, RISC-V doesn't support sub-word
> atomics which is used by this driver.

Why not? Compilers and libatomic do, so surely the Linux kernel should
too.

> Due to this, the build fails
> with below error.
> 
> In function ‘ssh_seq_next’,
>    inlined from ‘ssam_request_write_data’ at drivers/platform/surface/aggregator/controller.c:1483:8:
> ././include/linux/compiler_types.h:399:45: error: call to ‘__compiletime_assert_335’ declared with attribute error: BUILD_BUG failed
>  399 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
>      |                                             ^
> ./include/linux/compiler.h:78:45: note: in definition of macro ‘unlikely’
>   78 | # define unlikely(x)    __builtin_expect(!!(x), 0)
>      |                                             ^
> ././include/linux/compiler_types.h:387:9: note: in expansion of macro ‘__compiletime_assert’
>  387 |         __compiletime_assert(condition, msg, prefix, suffix)
>      |         ^~~~~~~~~~~~~~~~~~~~
> ././include/linux/compiler_types.h:399:9: note: in expansion of macro ‘_compiletime_assert’
>  399 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
>      |         ^~~~~~~~~~~~~~~~~~~
> ./include/linux/build_bug.h:39:37: note: in expansion of macro ‘compiletime_assert’
>   39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
>      |                                     ^~~~~~~~~~~~~~~~~~
> ./include/linux/build_bug.h:59:21: note: in expansion of macro ‘BUILD_BUG_ON_MSG’
>   59 | #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
>      |                     ^~~~~~~~~~~~~~~~
> ./arch/riscv/include/asm/cmpxchg.h:335:17: note: in expansion of macro ‘BUILD_BUG’
>  335 |                 BUILD_BUG();                                            \
>      |                 ^~~~~~~~~
> ./arch/riscv/include/asm/cmpxchg.h:344:30: note: in expansion of macro ‘__cmpxchg’
>  344 |         (__typeof__(*(ptr))) __cmpxchg((ptr),                           \
>      |                              ^~~~~~~~~
> ./include/linux/atomic/atomic-instrumented.h:1916:9: note: in expansion of macro ‘arch_cmpxchg’
> 1916 |         arch_cmpxchg(__ai_ptr, __VA_ARGS__); \
>      |         ^~~~~~~~~~~~
> drivers/platform/surface/aggregator/controller.c:61:32: note: in expansion of macro ‘cmpxchg’
>   61 |         while (unlikely((ret = cmpxchg(&c->value, old, new)) != old)) {
>      |                                ^~~~~~~
> 
> So, disable this driver for RISC-V even when ACPI is enabled for now.
> 
> Signed-off-by: Sunil V L <sunilvl@xxxxxxxxxxxxxxxx>
> ---
> drivers/platform/surface/aggregator/Kconfig | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/surface/aggregator/Kconfig b/drivers/platform/surface/aggregator/Kconfig
> index c114f9dd5fe1..88afc38ffdc5 100644
> --- a/drivers/platform/surface/aggregator/Kconfig
> +++ b/drivers/platform/surface/aggregator/Kconfig
> @@ -4,7 +4,7 @@
> menuconfig SURFACE_AGGREGATOR
> 	tristate "Microsoft Surface System Aggregator Module Subsystem and Drivers"
> 	depends on SERIAL_DEV_BUS
> -	depends on ACPI
> +	depends on ACPI && !RISCV

If you insist on doing this, at least make it some new config variable
that’s self-documenting and means this automatically gets re-enabled
when arch/riscv fixes this deficiency? Hard-coding arch lists like this
seems like a terrible anti-pattern.

Jess

> 	select CRC_CCITT
> 	help
> 	  The Surface System Aggregator Module (Surface SAM or SSAM) is an
> -- 
> 2.34.1
> 
> 
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