Received-SPF: pass (google.com: domain of linux-crypto-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <0c433e15-640e-280f-fcb0-a8fe081d1bcc@gmail.com>
Date:   Wed, 5 Apr 2023 11:33:00 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.9.1
Subject: Re: [PATCH V4 22/23] platform/surface: Disable for RISC-V
To:     Sunil V L <sunilvl@ventanamicro.com>, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org,
        linux-acpi@vger.kernel.org, linux-crypto@vger.kernel.org,
        platform-driver-x86@vger.kernel.org, llvm@lists.linux.dev
Cc:     Jonathan Corbet <corbet@lwn.net>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>, Len Brown <lenb@kernel.org>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Weili Qian <qianweili@huawei.com>,
        Zhou Wang <wangzhou1@hisilicon.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Marc Zyngier <maz@kernel.org>,
        Hans de Goede <hdegoede@redhat.com>,
        Mark Gross <markgross@kernel.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Tom Rix <trix@redhat.com>,
        "Rafael J . Wysocki" <rafael@kernel.org>,
        "David S . Miller" <davem@davemloft.net>
References: <20230404182037.863533-1-sunilvl@ventanamicro.com>
 <20230404182037.863533-23-sunilvl@ventanamicro.com>
Content-Language: en-US
From:   Maximilian Luz <luzmaximilian@gmail.com>
In-Reply-To: <20230404182037.863533-23-sunilvl@ventanamicro.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk

On 4/4/23 20:20, Sunil V L 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. Due to this, the build fails
> with below error.
> 
> In function â€˜ssh_seq_nextâ€™,
>      inlined from â€˜ssam_request_write_dataâ€™ at drivers/platform/surface/aggregator/controller.c:1483:8:
> ././include/linux/compiler_types.h:399:45: error: call to â€˜__compiletime_assert_335â€™ 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 â€˜unlikelyâ€™
>     78 | # define unlikely(x)    __builtin_expect(!!(x), 0)
>        |                                             ^
> ././include/linux/compiler_types.h:387:9: note: in expansion of macro â€˜__compiletime_assertâ€™
>    387 |         __compiletime_assert(condition, msg, prefix, suffix)
>        |         ^~~~~~~~~~~~~~~~~~~~
> ././include/linux/compiler_types.h:399:9: note: in expansion of macro â€˜_compiletime_assertâ€™
>    399 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
>        |         ^~~~~~~~~~~~~~~~~~~
> ./include/linux/build_bug.h:39:37: note: in expansion of macro â€˜compiletime_assertâ€™
>     39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
>        |                                     ^~~~~~~~~~~~~~~~~~
> ./include/linux/build_bug.h:59:21: note: in expansion of macro â€˜BUILD_BUG_ON_MSGâ€™
>     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 â€˜BUILD_BUGâ€™
>    335 |                 BUILD_BUG();                                            \
>        |                 ^~~~~~~~~
> ./arch/riscv/include/asm/cmpxchg.h:344:30: note: in expansion of macro â€˜__cmpxchgâ€™
>    344 |         (__typeof__(*(ptr))) __cmpxchg((ptr),                           \
>        |                              ^~~~~~~~~
> ./include/linux/atomic/atomic-instrumented.h:1916:9: note: in expansion of macro â€˜arch_cmpxchgâ€™
>   1916 |         arch_cmpxchg(__ai_ptr, __VA_ARGS__); \
>        |         ^~~~~~~~~~~~
> drivers/platform/surface/aggregator/controller.c:61:32: note: in expansion of macro â€˜cmpxchgâ€™
>     61 |         while (unlikely((ret = cmpxchg(&c->value, old, new)) != old)) {
>        |                                ^~~~~~~
> 
> So, disable this driver for RISC-V even when ACPI is enabled for now.

CONFIG_SURFACE_PLATFORMS should be enabled for ARM64 || X86 || COMPILE_TEST only,
so I guess the issue only happens when compiling with the latter enabled?

I'm not aware of any current plans of MS to release RISC-V-based Surface
devices, so you could maybe also just explicitly disable CONFIG_SURFACE_PLATFORMS.
In any case, I don't see any issues with disabling the whole platform/surface
or only individual drivers for RISC-V, so for either solution:

Acked-by: Maximilian Luz <luzmaximilian@gmail.com>

> Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
> ---
>   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
>   	select CRC_CCITT
>   	help
>   	  The Surface System Aggregator Module (Surface SAM or SSAM) is an