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From: "Uwe Kleine-König" <ukleinek@kernel.org>
To: FUJITA Tomonori <tomo@flapping.org>
Cc: fustini@kernel.org, guoren@kernel.org, wefu@redhat.com,
	 a.hindborg@kernel.org, acourbot@nvidia.com,
	aliceryhl@google.com,  bjorn3_gh@protonmail.com,
	boqun@kernel.org, dakr@kernel.org, daniel.almeida@collabora.com,
	 gary@garyguo.net, linux-riscv@lists.infradead.org,
	lossin@kernel.org,  m.wilczynski@samsung.com, ojeda@kernel.org,
	tamird@kernel.org, tmgross@umich.edu,  work@onurozkan.dev,
	linux-pwm@vger.kernel.org, rust-for-linux@vger.kernel.org,
	 fujita.tomonori@gmail.com, stable@vger.kernel.org
Subject: Re: [PATCH v2] pwm: th1520: Fix 32-bit build with COMPILE_TEST
Date: Thu, 1 Oct 2026 08:27:45 +0200	[thread overview]
Message-ID: <ar38qq0q8f2Vecuw@monoceros> (raw)
In-Reply-To: <20261001.070215.521963012921142699.tomo@flapping.org>


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Hello,

On Thu, Oct 01, 2026 at 07:02:15AM +0900, FUJITA Tomonori wrote:
> On Wed, 30 Sep 2026 13:57:31 +0200
> Uwe Kleine-König <ukleinek@kernel.org> wrote:
> 
> >> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> >> index 729776086879..abecd95b0c3c 100644
> >> --- a/drivers/pwm/Kconfig
> >> +++ b/drivers/pwm/Kconfig
> >> @@ -772,7 +772,7 @@ config PWM_TEGRA
> >>  
> >>  config PWM_TH1520
> >>  	tristate "TH1520 PWM support"
> >> -	depends on ARCH_THEAD || COMPILE_TEST
> >> +	depends on ARCH_THEAD || (COMPILE_TEST && 64BIT)
> >>  	depends on RUST
> >>  	depends on HAS_IOMEM && COMMON_CLK
> >>  	select RUST_PWM_ABSTRACTIONS
> > 
> > Can't we do better than that? For C code the right thing to do is to use
> > one of the div helpers instead of a plain / for types bigger than long.
> 
> Indeed. Rust code already uses some div helpers. However, the kernel
> crate does not have Rust wrappers for the helpers this driver needs,
> such as mul_u64_u64_div_u64(), so we need to add them first. The
> changes would be too large for stable.
> 
> So how about merging this as a fix? I will work on patches to use div
> helpers in the driver.

Fine, then let me just wonder about the expression you chose, that makes
it look as if 64BIT was only needed for COMPILE_TEST.

How about making this

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 729776086879..4cc2911a0673 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -774,6 +774,7 @@ config PWM_TH1520
 	tristate "TH1520 PWM support"
 	depends on ARCH_THEAD || COMPILE_TEST
 	depends on RUST
+	depends on 64BIT # no 64bit division available on 32 bit builds
 	depends on HAS_IOMEM && COMMON_CLK
 	select RUST_PWM_ABSTRACTIONS
 	help

instead?

Best regards
Uwe

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  reply	other threads:[~2026-10-01  6:28 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20260930101334eucas1p2ec64abcf499a296767711f13ad70c486@eucas1p2.samsung.com>
2026-09-30 10:12 ` [PATCH v2] pwm: th1520: Fix 32-bit build with COMPILE_TEST FUJITA Tomonori
2026-09-30 10:27   ` Miguel Ojeda
2026-09-30 10:33   ` Michal Wilczynski
2026-09-30 11:57   ` Uwe Kleine-König
2026-09-30 22:02     ` FUJITA Tomonori
2026-10-01  6:27       ` Uwe Kleine-König [this message]
2026-10-01  9:07         ` FUJITA Tomonori

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