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;
Date:   Wed, 5 Apr 2023 16:59:18 +0530
From:   Sunil V L <sunilvl@ventanamicro.com>
To:     Jessica Clarke <jrtc27@jrtc27.com>
Cc:     linux-doc@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-riscv <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,
        Weili Qian <qianweili@huawei.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Tom Rix <trix@redhat.com>, Jonathan Corbet <corbet@lwn.net>,
        Marc Zyngier <maz@kernel.org>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Mark Gross <markgross@kernel.org>,
        Hans de Goede <hdegoede@redhat.com>,
        Zhou Wang <wangzhou1@hisilicon.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        "Rafael J . Wysocki" <rafael@kernel.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Maximilian Luz <luzmaximilian@gmail.com>,
        "David S . Miller" <davem@davemloft.net>,
        Len Brown <lenb@kernel.org>
Subject: Re: [PATCH V4 22/23] platform/surface: Disable for RISC-V
Message-ID: <ZC1bjmdMqYqSnIHP@sunil-laptop>
References: <20230404182037.863533-1-sunilvl@ventanamicro.com>
 <20230404182037.863533-23-sunilvl@ventanamicro.com>
 <EAC85F14-B1DA-4358-9042-A607436D582A@jrtc27.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <EAC85F14-B1DA-4358-9042-A607436D582A@jrtc27.com>
Precedence: bulk

Hi Jess,

On Wed, Apr 05, 2023 at 05:19:35AM +0100, Jessica Clarke wrote:
> On 4 Apr 2023, at 19:20, Sunil V L <sunilvl@ventanamicro.com> 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.
>
I think you are probably right. But I don't want to combine that
activity with this series. IMO, that should be separate activity.
 
> > 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.
> > 
> > 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
> 
> 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.
> 
I understand your point. But given that this is currently only issue with
a single driver from Microsoft and that too only in COMPILE_TEST builds,
I think introducing a new config variable is overkill. If we support
sub-word atomics in kernel, the option may not be useful much anyway.

There are patterns to disable an architecture for COMPILE_TEST builds.

Thanks,
Sunil