[PATCH] pwm: th1520: fix `CLIPPY=1` warning

[PATCH] pwm: th1520: fix `CLIPPY=1` warning

[Miguel Ojeda]

The Rust kernel code should be kept `CLIPPY=1`-clean [1].

Clippy reports:

    error: this pattern reimplements `Option::unwrap_or`
      --> drivers/pwm/pwm_th1520.rs:64:5
       |
    64 | /     (match ns.checked_mul(rate_hz) {
    65 | |         Some(product) => product,
    66 | |         None => u64::MAX,
    67 | |     }) / NSEC_PER_SEC_U64
       | |______^ help: replace with: `ns.checked_mul(rate_hz).unwrap_or(u64::MAX)`
       |
       = help: for further information visit https://rust-lang.github.io/rust-clippy/rust-1.92.0/index.html#manual_unwrap_or
       = note: `-D clippy::manual-unwrap-or` implied by `-D warnings`
       = help: to override `-D warnings` add `#[allow(clippy::manual_unwrap_or)]`

Applying the suggestion then triggers:

    error: manual saturating arithmetic
      --> drivers/pwm/pwm_th1520.rs:64:5
       |
    64 |     ns.checked_mul(rate_hz).unwrap_or(u64::MAX) / NSEC_PER_SEC_U64
       |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `saturating_mul`: `ns.saturating_mul(rate_hz)`
       |
       = help: for further information visit https://rust-lang.github.io/rust-clippy/rust-1.92.0/index.html#manual_saturating_arithmetic
       = note: `-D clippy::manual-saturating-arithmetic` implied by `-D warnings`
       = help: to override `-D warnings` add `#[allow(clippy::manual_saturating_arithmetic)]`

Thus fix it by using saturating arithmatic, which simplifies the code
as well.

Link: https://rust-for-linux.com/contributing#submit-checklist-addendum [1]
Fixes: e03724aac758 ("pwm: Add Rust driver for T-HEAD TH1520 SoC")
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
It would be nice to clean this up, so that Mark may start enforcing it
in linux-next -- thanks!

Completely untested, so please beware. Also, I am not sure if I am
missing something here, since saturation arithmetic is already used
a few lines below already.

Cc: Mark Brown <broonie@kernel.org>

 drivers/pwm/pwm_th1520.rs | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/pwm/pwm_th1520.rs b/drivers/pwm/pwm_th1520.rs
index 21b4bdaf0607..fb95f994f963 100644
--- a/drivers/pwm/pwm_th1520.rs
+++ b/drivers/pwm/pwm_th1520.rs
@@ -61,10 +61,7 @@ const fn th1520_pwm_fp(n: u32) -> usize {
 fn ns_to_cycles(ns: u64, rate_hz: u64) -> u64 {
     const NSEC_PER_SEC_U64: u64 = time::NSEC_PER_SEC as u64;

-    (match ns.checked_mul(rate_hz) {
-        Some(product) => product,
-        None => u64::MAX,
-    }) / NSEC_PER_SEC_U64
+    ns.saturating_mul(rate_hz) / NSEC_PER_SEC_U64
 }

 fn cycles_to_ns(cycles: u64, rate_hz: u64) -> u64 {

base-commit: e3b32dcb9f23e3c3927ef3eec6a5842a988fb574
--
2.52.0

Re: [PATCH] pwm: th1520: fix `CLIPPY=1` warning

[Danilo Krummrich]

On Wed Jan 21, 2026 at 7:37 PM CET, Miguel Ojeda wrote:
> The Rust kernel code should be kept `CLIPPY=1`-clean [1].
>
> Clippy reports:
>
>     error: this pattern reimplements `Option::unwrap_or`
>       --> drivers/pwm/pwm_th1520.rs:64:5
>        |
>     64 | /     (match ns.checked_mul(rate_hz) {
>     65 | |         Some(product) => product,
>     66 | |         None => u64::MAX,
>     67 | |     }) / NSEC_PER_SEC_U64
>        | |______^ help: replace with: `ns.checked_mul(rate_hz).unwrap_or(u64::MAX)`
>        |
>        = help: for further information visit https://rust-lang.github.io/rust-clippy/rust-1.92.0/index.html#manual_unwrap_or
>        = note: `-D clippy::manual-unwrap-or` implied by `-D warnings`
>        = help: to override `-D warnings` add `#[allow(clippy::manual_unwrap_or)]`
>
> Applying the suggestion then triggers:
>
>     error: manual saturating arithmetic
>       --> drivers/pwm/pwm_th1520.rs:64:5
>        |
>     64 |     ns.checked_mul(rate_hz).unwrap_or(u64::MAX) / NSEC_PER_SEC_U64
>        |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `saturating_mul`: `ns.saturating_mul(rate_hz)`
>        |
>        = help: for further information visit https://rust-lang.github.io/rust-clippy/rust-1.92.0/index.html#manual_saturating_arithmetic
>        = note: `-D clippy::manual-saturating-arithmetic` implied by `-D warnings`
>        = help: to override `-D warnings` add `#[allow(clippy::manual_saturating_arithmetic)]`
>
> Thus fix it by using saturating arithmatic, which simplifies the code
> as well.
>
> Link: https://rust-for-linux.com/contributing#submit-checklist-addendum [1]
> Fixes: e03724aac758 ("pwm: Add Rust driver for T-HEAD TH1520 SoC")
> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
> ---
> It would be nice to clean this up, so that Mark may start enforcing it
> in linux-next -- thanks!

Indeed, the patch itself LGTM.

Reviewed-by: Danilo Krummrich <dakr@kernel.org>

Re: [PATCH] pwm: th1520: fix `CLIPPY=1` warning

[Miguel Ojeda]

On Wed, Jan 21, 2026 at 7:37 PM Miguel Ojeda <ojeda@kernel.org> wrote:
>
> The Rust kernel code should be kept `CLIPPY=1`-clean [1].
>
> Clippy reports:
>
>     error: this pattern reimplements `Option::unwrap_or`
>       --> drivers/pwm/pwm_th1520.rs:64:5
>        |
>     64 | /     (match ns.checked_mul(rate_hz) {
>     65 | |         Some(product) => product,
>     66 | |         None => u64::MAX,
>     67 | |     }) / NSEC_PER_SEC_U64
>        | |______^ help: replace with: `ns.checked_mul(rate_hz).unwrap_or(u64::MAX)`
>        |
>        = help: for further information visit https://rust-lang.github.io/rust-clippy/rust-1.92.0/index.html#manual_unwrap_or
>        = note: `-D clippy::manual-unwrap-or` implied by `-D warnings`
>        = help: to override `-D warnings` add `#[allow(clippy::manual_unwrap_or)]`
>
> Applying the suggestion then triggers:
>
>     error: manual saturating arithmetic
>       --> drivers/pwm/pwm_th1520.rs:64:5
>        |
>     64 |     ns.checked_mul(rate_hz).unwrap_or(u64::MAX) / NSEC_PER_SEC_U64
>        |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `saturating_mul`: `ns.saturating_mul(rate_hz)`
>        |
>        = help: for further information visit https://rust-lang.github.io/rust-clippy/rust-1.92.0/index.html#manual_saturating_arithmetic
>        = note: `-D clippy::manual-saturating-arithmetic` implied by `-D warnings`
>        = help: to override `-D warnings` add `#[allow(clippy::manual_saturating_arithmetic)]`
>
> Thus fix it by using saturating arithmatic, which simplifies the code
> as well.
>
> Link: https://rust-for-linux.com/contributing#submit-checklist-addendum [1]
> Fixes: e03724aac758 ("pwm: Add Rust driver for T-HEAD TH1520 SoC")
> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Pinging about this...

Adding Michal and Uwe to Cc in case it helps (the driver is under
"RISC-V THEAD SoC SUPPORT" so they don't get paged).

Thanks!

Cheers,
Miguel

Re: [PATCH] pwm: th1520: fix `CLIPPY=1` warning

[Uwe Kleine-König]

[-- Attachment #1: Type: text/plain, Size: 2032 bytes --]

Hello Miguel,

On Wed, Jan 21, 2026 at 07:37:19PM +0100, Miguel Ojeda wrote:
> The Rust kernel code should be kept `CLIPPY=1`-clean [1].
> 
> Clippy reports:
> 
>     error: this pattern reimplements `Option::unwrap_or`
>       --> drivers/pwm/pwm_th1520.rs:64:5
>        |
>     64 | /     (match ns.checked_mul(rate_hz) {
>     65 | |         Some(product) => product,
>     66 | |         None => u64::MAX,
>     67 | |     }) / NSEC_PER_SEC_U64
>        | |______^ help: replace with: `ns.checked_mul(rate_hz).unwrap_or(u64::MAX)`
>        |
>        = help: for further information visit https://rust-lang.github.io/rust-clippy/rust-1.92.0/index.html#manual_unwrap_or
>        = note: `-D clippy::manual-unwrap-or` implied by `-D warnings`
>        = help: to override `-D warnings` add `#[allow(clippy::manual_unwrap_or)]`
> 
> Applying the suggestion then triggers:
> 
>     error: manual saturating arithmetic
>       --> drivers/pwm/pwm_th1520.rs:64:5
>        |
>     64 |     ns.checked_mul(rate_hz).unwrap_or(u64::MAX) / NSEC_PER_SEC_U64
>        |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `saturating_mul`: `ns.saturating_mul(rate_hz)`
>        |
>        = help: for further information visit https://rust-lang.github.io/rust-clippy/rust-1.92.0/index.html#manual_saturating_arithmetic
>        = note: `-D clippy::manual-saturating-arithmetic` implied by `-D warnings`
>        = help: to override `-D warnings` add `#[allow(clippy::manual_saturating_arithmetic)]`
> 
> Thus fix it by using saturating arithmatic, which simplifies the code
> as well.
> 
> Link: https://rust-for-linux.com/contributing#submit-checklist-addendum [1]
> Fixes: e03724aac758 ("pwm: Add Rust driver for T-HEAD TH1520 SoC")
> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
> ---

Looks good to me. I'll wait for Michal to add his blessing and then when
picking it up tend to drop the Fixes line. Or do we also care about
CLIPPY-cleanness in stable?

Best regards
Uwe

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Re: [PATCH] pwm: th1520: fix `CLIPPY=1` warning

[Alice Ryhl]

On Mon, Feb 9, 2026 at 9:56 AM Uwe Kleine-König
<u.kleine-koenig@baylibre.com> wrote:
>
> Hello Miguel,
>
> On Wed, Jan 21, 2026 at 07:37:19PM +0100, Miguel Ojeda wrote:
> > The Rust kernel code should be kept `CLIPPY=1`-clean [1].
> >
> > Clippy reports:
> >
> >     error: this pattern reimplements `Option::unwrap_or`
> >       --> drivers/pwm/pwm_th1520.rs:64:5
> >        |
> >     64 | /     (match ns.checked_mul(rate_hz) {
> >     65 | |         Some(product) => product,
> >     66 | |         None => u64::MAX,
> >     67 | |     }) / NSEC_PER_SEC_U64
> >        | |______^ help: replace with: `ns.checked_mul(rate_hz).unwrap_or(u64::MAX)`
> >        |
> >        = help: for further information visit https://rust-lang.github.io/rust-clippy/rust-1.92.0/index.html#manual_unwrap_or
> >        = note: `-D clippy::manual-unwrap-or` implied by `-D warnings`
> >        = help: to override `-D warnings` add `#[allow(clippy::manual_unwrap_or)]`
> >
> > Applying the suggestion then triggers:
> >
> >     error: manual saturating arithmetic
> >       --> drivers/pwm/pwm_th1520.rs:64:5
> >        |
> >     64 |     ns.checked_mul(rate_hz).unwrap_or(u64::MAX) / NSEC_PER_SEC_U64
> >        |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `saturating_mul`: `ns.saturating_mul(rate_hz)`
> >        |
> >        = help: for further information visit https://rust-lang.github.io/rust-clippy/rust-1.92.0/index.html#manual_saturating_arithmetic
> >        = note: `-D clippy::manual-saturating-arithmetic` implied by `-D warnings`
> >        = help: to override `-D warnings` add `#[allow(clippy::manual_saturating_arithmetic)]`
> >
> > Thus fix it by using saturating arithmatic, which simplifies the code
> > as well.
> >
> > Link: https://rust-for-linux.com/contributing#submit-checklist-addendum [1]
> > Fixes: e03724aac758 ("pwm: Add Rust driver for T-HEAD TH1520 SoC")
> > Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
> > ---
>
> Looks good to me. I'll wait for Michal to add his blessing and then when
> picking it up tend to drop the Fixes line. Or do we also care about
> CLIPPY-cleanness in stable?

I think we do care about that.

Alice

Re: [PATCH] pwm: th1520: fix `CLIPPY=1` warning

[Michal Wilczynski]

On 2/9/26 09:56, Uwe Kleine-König wrote:
> Hello Miguel,
> 
> On Wed, Jan 21, 2026 at 07:37:19PM +0100, Miguel Ojeda wrote:
>> The Rust kernel code should be kept `CLIPPY=1`-clean [1].
>>
>> Clippy reports:
>>
>>     error: this pattern reimplements `Option::unwrap_or`
>>       --> drivers/pwm/pwm_th1520.rs:64:5
>>        |
>>     64 | /     (match ns.checked_mul(rate_hz) {
>>     65 | |         Some(product) => product,
>>     66 | |         None => u64::MAX,
>>     67 | |     }) / NSEC_PER_SEC_U64
>>        | |______^ help: replace with: `ns.checked_mul(rate_hz).unwrap_or(u64::MAX)`
>>        |
>>        = help: for further information visit https://protect2.fireeye.com/v1/url?k=4a8755d5-151b7cff-4a86de9a-000babe598f7-51498316c06f2766&q=1&e=b527c3ac-a0b8-4074-9bc4-c3497f7913a5&u=https%3A%2F%2Frust-lang.github.io%2Frust-clippy%2Frust-1.92.0%2Findex.html%23manual_unwrap_or
>>        = note: `-D clippy::manual-unwrap-or` implied by `-D warnings`
>>        = help: to override `-D warnings` add `#[allow(clippy::manual_unwrap_or)]`
>>
>> Applying the suggestion then triggers:
>>
>>     error: manual saturating arithmetic
>>       --> drivers/pwm/pwm_th1520.rs:64:5
>>        |
>>     64 |     ns.checked_mul(rate_hz).unwrap_or(u64::MAX) / NSEC_PER_SEC_U64
>>        |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `saturating_mul`: `ns.saturating_mul(rate_hz)`
>>        |
>>        = help: for further information visit https://protect2.fireeye.com/v1/url?k=7fd7ef65-204bc64f-7fd6642a-000babe598f7-c6165289323e3bed&q=1&e=b527c3ac-a0b8-4074-9bc4-c3497f7913a5&u=https%3A%2F%2Frust-lang.github.io%2Frust-clippy%2Frust-1.92.0%2Findex.html%23manual_saturating_arithmetic
>>        = note: `-D clippy::manual-saturating-arithmetic` implied by `-D warnings`
>>        = help: to override `-D warnings` add `#[allow(clippy::manual_saturating_arithmetic)]`
>>
>> Thus fix it by using saturating arithmatic, which simplifies the code
>> as well.
>>
>> Link: https://protect2.fireeye.com/v1/url?k=3f9f72c4-60035bee-3f9ef98b-000babe598f7-ce3556202281f48e&q=1&e=b527c3ac-a0b8-4074-9bc4-c3497f7913a5&u=https%3A%2F%2Frust-for-linux.com%2Fcontributing%23submit-checklist-addendum [1]
>> Fixes: e03724aac758 ("pwm: Add Rust driver for T-HEAD TH1520 SoC")
>> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
>> ---
> 
> Looks good to me. I'll wait for Michal to add his blessing and then when
> picking it up tend to drop the Fixes line. Or do we also care about
> CLIPPY-cleanness in stable?

Hmm I'm pretty sure at the time of the writing building with CLIPPY
didn't trigger this warning, so I guess it's either a newer version of
CLIPPY that I used or in the meantime CLIPPY was updated.

Anyway 
Reviewed-by: Michal Wilczynski <m.wilczynski@samsung.com>

> 
> Best regards
> Uwe

Best regards,
-- 
Michal Wilczynski <m.wilczynski@samsung.com>

Re: [PATCH] pwm: th1520: fix `CLIPPY=1` warning

[Miguel Ojeda]

On Mon, Feb 9, 2026 at 9:56 AM Uwe Kleine-König
<u.kleine-koenig@baylibre.com> wrote:
>
> Looks good to me. I'll wait for Michal to add his blessing and then when
> picking it up tend to drop the Fixes line. Or do we also care about
> CLIPPY-cleanness in stable?

Yeah, so far we do. At least, back then we decided we would try our
best to keep them clean, and I build the stable and LTS kernels with
Clippy enabled (and I think some downstream users may do development
based on those, so I hope that effort helps).

Worst case, we can always drop that requirement.

In any case, some of these patches, even if not considered Fixes (e.g.
a new lint), sometimes they may need to go "urgently" into `-fixes`
branches rather than `-next` ones, i.e. even without such a tag; and
we can also still send them to stable -- what I usually give the
stable team is a line like:

    Cc: stable@vger.kernel.org # Needed in 6.12.y and later (Rust is
pinned in older LTSs).

I hope that helps!

Cheers,
Miguel

Re: [PATCH] pwm: th1520: fix `CLIPPY=1` warning

[Benno Lossin]

On Wed Jan 21, 2026 at 7:37 PM CET, Miguel Ojeda wrote:
> The Rust kernel code should be kept `CLIPPY=1`-clean [1].
>
> Clippy reports:
>
>     error: this pattern reimplements `Option::unwrap_or`
>       --> drivers/pwm/pwm_th1520.rs:64:5
>        |
>     64 | /     (match ns.checked_mul(rate_hz) {
>     65 | |         Some(product) => product,
>     66 | |         None => u64::MAX,
>     67 | |     }) / NSEC_PER_SEC_U64
>        | |______^ help: replace with: `ns.checked_mul(rate_hz).unwrap_or(u64::MAX)`
>        |
>        = help: for further information visit https://rust-lang.github.io/rust-clippy/rust-1.92.0/index.html#manual_unwrap_or
>        = note: `-D clippy::manual-unwrap-or` implied by `-D warnings`
>        = help: to override `-D warnings` add `#[allow(clippy::manual_unwrap_or)]`
>
> Applying the suggestion then triggers:
>
>     error: manual saturating arithmetic
>       --> drivers/pwm/pwm_th1520.rs:64:5
>        |
>     64 |     ns.checked_mul(rate_hz).unwrap_or(u64::MAX) / NSEC_PER_SEC_U64
>        |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `saturating_mul`: `ns.saturating_mul(rate_hz)`
>        |
>        = help: for further information visit https://rust-lang.github.io/rust-clippy/rust-1.92.0/index.html#manual_saturating_arithmetic
>        = note: `-D clippy::manual-saturating-arithmetic` implied by `-D warnings`
>        = help: to override `-D warnings` add `#[allow(clippy::manual_saturating_arithmetic)]`
>
> Thus fix it by using saturating arithmatic, which simplifies the code
> as well.
>
> Link: https://rust-for-linux.com/contributing#submit-checklist-addendum [1]
> Fixes: e03724aac758 ("pwm: Add Rust driver for T-HEAD TH1520 SoC")
> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Just encountered this during my testing, could we get this picked up please?

Cheers,
Benno

> ---
> It would be nice to clean this up, so that Mark may start enforcing it
> in linux-next -- thanks!
>
> Completely untested, so please beware. Also, I am not sure if I am
> missing something here, since saturation arithmetic is already used
> a few lines below already.
>
> Cc: Mark Brown <broonie@kernel.org>
>
>  drivers/pwm/pwm_th1520.rs | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)

Re: [PATCH] pwm: th1520: fix `CLIPPY=1` warning

[Miguel Ojeda]

On Mon, Feb 9, 2026 at 9:56 AM Uwe Kleine-König
<u.kleine-koenig@baylibre.com> wrote:
>
> Looks good to me. I'll wait for Michal to add his blessing and then when
> picking it up tend to drop the Fixes line. Or do we also care about
> CLIPPY-cleanness in stable?

Do you plan on picking this one up? Michal already reviewed it.

Thanks!

Cheers,
Miguel