[PATCH] iio: frequency: ad983x: replace do_div() with div64_ul().

[PATCH] iio: frequency: ad983x: replace do_div() with div64_ul().

[Joshua Crofts]

Coccinelle reported the following in both ad983x drivers:
do_div() does a 64-by-32 division, please consider using
div64_ul instead.

Fix this by replacing do_div() with div64_ul(), which
safely handles 64-bit dividends and unsigned long
divisors across all architectures.

Signed-off-by: Joshua Crofts <joshua.crofts1@gmail.com>
---
 drivers/staging/iio/frequency/ad9832.c | 3 ++-
 drivers/staging/iio/frequency/ad9834.c | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/iio/frequency/ad9832.c b/drivers/staging/iio/frequency/ad9832.c
index b87ea1781b..61ee93263a 100644
--- a/drivers/staging/iio/frequency/ad9832.c
+++ b/drivers/staging/iio/frequency/ad9832.c
@@ -13,6 +13,7 @@
 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/kernel.h>
+#include <linux/math64.h>
 #include <linux/module.h>
 #include <linux/regulator/consumer.h>
 #include <linux/slab.h>
@@ -115,7 +116,7 @@ static unsigned long ad9832_calc_freqreg(unsigned long mclk, unsigned long fout)
 {
 	unsigned long long freqreg = (u64)fout *
 				     (u64)((u64)1L << AD9832_FREQ_BITS);
-	do_div(freqreg, mclk);
+	freqreg = div64_ul(freqreg, mclk);
 	return freqreg;
 }
 
diff --git a/drivers/staging/iio/frequency/ad9834.c b/drivers/staging/iio/frequency/ad9834.c
index d339d5e8e0..83d0e1360c 100644
--- a/drivers/staging/iio/frequency/ad9834.c
+++ b/drivers/staging/iio/frequency/ad9834.c
@@ -10,6 +10,7 @@
 #include <linux/workqueue.h>
 #include <linux/device.h>
 #include <linux/kernel.h>
+#include <linux/math64.h>
 #include <linux/slab.h>
 #include <linux/sysfs.h>
 #include <linux/list.h>
@@ -101,7 +102,7 @@ static unsigned int ad9834_calc_freqreg(unsigned long mclk, unsigned long fout)
 {
 	unsigned long long freqreg = (u64)fout * (u64)BIT(AD9834_FREQ_BITS);
 
-	do_div(freqreg, mclk);
+	freqreg = div64_ul(freqreg, mclk);
 	return freqreg;
 }
 
-- 
2.47.3

Re: [PATCH] iio: frequency: ad983x: replace do_div() with div64_ul().

[Joshua Crofts]

On Thu, 9 Apr 2026 at 15:18, Joshua Crofts <joshua.crofts1@gmail.com> wrote:
>
> Coccinelle reported the following in both ad983x drivers:
> do_div() does a 64-by-32 division, please consider using
> div64_ul instead.

Apologies, I typoed Greg's and Nuno's emails in the original CC list.

-- 
Kind regards

CJD

Re: [PATCH] iio: frequency: ad983x: replace do_div() with div64_ul().

[Greg KH]

On Thu, Apr 09, 2026 at 03:34:02PM +0200, Joshua Crofts wrote:
> On Thu, 9 Apr 2026 at 15:18, Joshua Crofts <joshua.crofts1@gmail.com> wrote:
> >
> > Coccinelle reported the following in both ad983x drivers:
> > do_div() does a 64-by-32 division, please consider using
> > div64_ul instead.
> 
> Apologies, I typoed Greg's and Nuno's emails in the original CC list.

Please send a v2 with that, as we didn't get this message at all :(

thanks,

greg k-h

[PATCH v2] iio: frequency: ad983x: replace do_div() with div64_ul().

[Joshua Crofts]

Coccinelle reported the following in both ad983x drivers:
do_div() does a 64-by-32 division, please consider using
div64_ul instead.

Fix this by replacing do_div() with div64_ul(), which
safely handles 64-bit dividends and unsigned long
divisors across all architectures.

Signed-off-by: Joshua Crofts <joshua.crofts1@gmail.com>
---
v2:
 - resent email with corrected addresses

 drivers/staging/iio/frequency/ad9832.c | 3 ++-
 drivers/staging/iio/frequency/ad9834.c | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/iio/frequency/ad9832.c b/drivers/staging/iio/frequency/ad9832.c
index b87ea1781b..61ee93263a 100644
--- a/drivers/staging/iio/frequency/ad9832.c
+++ b/drivers/staging/iio/frequency/ad9832.c
@@ -13,6 +13,7 @@
 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/kernel.h>
+#include <linux/math64.h>
 #include <linux/module.h>
 #include <linux/regulator/consumer.h>
 #include <linux/slab.h>
@@ -115,7 +116,7 @@ static unsigned long ad9832_calc_freqreg(unsigned long mclk, unsigned long fout)
 {
 	unsigned long long freqreg = (u64)fout *
 				     (u64)((u64)1L << AD9832_FREQ_BITS);
-	do_div(freqreg, mclk);
+	freqreg = div64_ul(freqreg, mclk);
 	return freqreg;
 }
 
diff --git a/drivers/staging/iio/frequency/ad9834.c b/drivers/staging/iio/frequency/ad9834.c
index d339d5e8e0..83d0e1360c 100644
--- a/drivers/staging/iio/frequency/ad9834.c
+++ b/drivers/staging/iio/frequency/ad9834.c
@@ -10,6 +10,7 @@
 #include <linux/workqueue.h>
 #include <linux/device.h>
 #include <linux/kernel.h>
+#include <linux/math64.h>
 #include <linux/slab.h>
 #include <linux/sysfs.h>
 #include <linux/list.h>
@@ -101,7 +102,7 @@ static unsigned int ad9834_calc_freqreg(unsigned long mclk, unsigned long fout)
 {
 	unsigned long long freqreg = (u64)fout * (u64)BIT(AD9834_FREQ_BITS);
 
-	do_div(freqreg, mclk);
+	freqreg = div64_ul(freqreg, mclk);
 	return freqreg;
 }
 
-- 
2.47.3

Re: [PATCH v2] iio: frequency: ad983x: replace do_div() with div64_ul().

[David Lechner]

On 4/9/26 10:01 AM, Joshua Crofts wrote:
> Coccinelle reported the following in both ad983x drivers:
> do_div() does a 64-by-32 division, please consider using
> div64_ul instead.
> 
> Fix this by replacing do_div() with div64_ul(), which
> safely handles 64-bit dividends and unsigned long
> divisors across all architectures.
> 
> Signed-off-by: Joshua Crofts <joshua.crofts1@gmail.com>
> ---
> v2:

Please don't send v2 or later revisions in reply to v1. It breaks
some workflows. Start a new thread instead.

>  - resent email with corrected addresses

Instead of a v2, you can just add a RESEND prefix to the subject line
in cases like this. But do include an explanation like this when you
do that.

> 
>  drivers/staging/iio/frequency/ad9832.c | 3 ++-
>  drivers/staging/iio/frequency/ad9834.c | 3 ++-
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/iio/frequency/ad9832.c b/drivers/staging/iio/frequency/ad9832.c
> index b87ea1781b..61ee93263a 100644
> --- a/drivers/staging/iio/frequency/ad9832.c
> +++ b/drivers/staging/iio/frequency/ad9832.c
> @@ -13,6 +13,7 @@
>  #include <linux/device.h>
>  #include <linux/err.h>
>  #include <linux/kernel.h>
> +#include <linux/math64.h>
>  #include <linux/module.h>
>  #include <linux/regulator/consumer.h>
>  #include <linux/slab.h>
> @@ -115,7 +116,7 @@ static unsigned long ad9832_calc_freqreg(unsigned long mclk, unsigned long fout)
>  {
>  	unsigned long long freqreg = (u64)fout *
>  				     (u64)((u64)1L << AD9832_FREQ_BITS);

I would expect checkpatch to complain that there is no blank line
between variable declarations and the rest of the code here.

> -	do_div(freqreg, mclk);
> +	freqreg = div64_ul(freqreg, mclk);
>  	return freqreg;

We can just return directly now.

	return div64_ul(freqreg, mclk);

>  }
>  
> diff --git a/drivers/staging/iio/frequency/ad9834.c b/drivers/staging/iio/frequency/ad9834.c
> index d339d5e8e0..83d0e1360c 100644
> --- a/drivers/staging/iio/frequency/ad9834.c
> +++ b/drivers/staging/iio/frequency/ad9834.c
> @@ -10,6 +10,7 @@
>  #include <linux/workqueue.h>
>  #include <linux/device.h>
>  #include <linux/kernel.h>
> +#include <linux/math64.h>
>  #include <linux/slab.h>
>  #include <linux/sysfs.h>
>  #include <linux/list.h>
> @@ -101,7 +102,7 @@ static unsigned int ad9834_calc_freqreg(unsigned long mclk, unsigned long fout)
>  {
>  	unsigned long long freqreg = (u64)fout * (u64)BIT(AD9834_FREQ_BITS);
>  
> -	do_div(freqreg, mclk);
> +	freqreg = div64_ul(freqreg, mclk);
>  	return freqreg;

ditto.

>  }
>  

Re: [PATCH v2] iio: frequency: ad983x: replace do_div() with div64_ul().

[Andy Shevchenko]

On Thu, Apr 09, 2026 at 10:39:07AM -0500, David Lechner wrote:
> On 4/9/26 10:01 AM, Joshua Crofts wrote:
> > Coccinelle reported the following in both ad983x drivers:
> > do_div() does a 64-by-32 division, please consider using
> > div64_ul instead.
> > 
> > Fix this by replacing do_div() with div64_ul(), which
> > safely handles 64-bit dividends and unsigned long
> > divisors across all architectures.
> > 
> > Signed-off-by: Joshua Crofts <joshua.crofts1@gmail.com>
> > ---
> > v2:
> 
> Please don't send v2 or later revisions in reply to v1. It breaks
> some workflows. Start a new thread instead.

> >  - resent email with corrected addresses
> 
> Instead of a v2, you can just add a RESEND prefix to the subject line
> in cases like this. But do include an explanation like this when you
> do that.

Nevertheless my comments still applicable to v2. The also Documented
recommendation to avoid sending new versions earlier than 24h.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH] iio: frequency: ad983x: replace do_div() with div64_ul().

[Andy Shevchenko]

On Thu, Apr 09, 2026 at 01:18:23PM +0000, Joshua Crofts wrote:
> Coccinelle reported the following in both ad983x drivers:
> do_div() does a 64-by-32 division, please consider using
> div64_ul instead.

div64_ul()

> Fix this by replacing do_div() with div64_ul(), which
> safely handles 64-bit dividends and unsigned long
> divisors across all architectures.

You should really dive into this code, it has more to work on...

...

>  #include <linux/device.h>
>  #include <linux/err.h>

>  #include <linux/kernel.h>

Consider replacing "proxy" headers at some point. (Not related to this patch,
though.)

> +#include <linux/math64.h>
>  #include <linux/module.h>
>  #include <linux/regulator/consumer.h>
>  #include <linux/slab.h>

...

> static unsigned long ad9832_calc_freqreg(unsigned long mclk, unsigned long fout)
>  {
>  	unsigned long long freqreg = (u64)fout *
>  				     (u64)((u64)1L << AD9832_FREQ_BITS);

(u64)1L is a fancy way of doing 1ULL. The second (u64) is also redundant and
altogether it's just a BIT_ULL(). But, check the value of _FREQ_BITS. If it's less than 32, the whole train of nonsense can be collapsed just to a BIT().

> -	do_div(freqreg, mclk);
> +	freqreg = div64_ul(freqreg, mclk);
>  	return freqreg;
>  }

...

> --- a/drivers/staging/iio/frequency/ad9834.c
> +++ b/drivers/staging/iio/frequency/ad9834.c
> @@ -10,6 +10,7 @@
>  #include <linux/workqueue.h>
>  #include <linux/device.h>
>  #include <linux/kernel.h>
> +#include <linux/math64.h>

Side note as per above.

>  #include <linux/slab.h>
>  #include <linux/sysfs.h>
>  #include <linux/list.h>
> @@ -101,7 +102,7 @@ static unsigned int ad9834_calc_freqreg(unsigned long mclk, unsigned long fout)
>  {
>  	unsigned long long freqreg = (u64)fout * (u64)BIT(AD9834_FREQ_BITS);
>  
> -	do_div(freqreg, mclk);
> +	freqreg = div64_ul(freqreg, mclk);
>  	return freqreg;
>  }

Ditto. Also split changes on per-driver basis.

...

So, if you go suggested way, I would expect to have 4 patches (2 series by 2
patches each) out of this one.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH] iio: frequency: ad983x: replace do_div() with div64_ul().

[David Laight]

On Thu,  9 Apr 2026 13:18:23 +0000
Joshua Crofts <joshua.crofts1@gmail.com> wrote:

> Coccinelle reported the following in both ad983x drivers:
> do_div() does a 64-by-32 division, please consider using
> div64_ul instead.
> 
> Fix this by replacing do_div() with div64_ul(), which
> safely handles 64-bit dividends and unsigned long
> divisors across all architectures.

Except here you have clock frequencies.
Either they fit in 32bits or they don't.
So the value shouldn't be 'unsigned long', but either u32 or u64.

You need to check the domain of the values, coccinelle is just looking
at the types.
Even with mclk being 'unsigned long' the code is fine provided the
frequency is below 4.2GHz.

So you are probably fixing nothing.

	David

> 
> Signed-off-by: Joshua Crofts <joshua.crofts1@gmail.com>
> ---
>  drivers/staging/iio/frequency/ad9832.c | 3 ++-
>  drivers/staging/iio/frequency/ad9834.c | 3 ++-
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/iio/frequency/ad9832.c b/drivers/staging/iio/frequency/ad9832.c
> index b87ea1781b..61ee93263a 100644
> --- a/drivers/staging/iio/frequency/ad9832.c
> +++ b/drivers/staging/iio/frequency/ad9832.c
> @@ -13,6 +13,7 @@
>  #include <linux/device.h>
>  #include <linux/err.h>
>  #include <linux/kernel.h>
> +#include <linux/math64.h>
>  #include <linux/module.h>
>  #include <linux/regulator/consumer.h>
>  #include <linux/slab.h>
> @@ -115,7 +116,7 @@ static unsigned long ad9832_calc_freqreg(unsigned long mclk, unsigned long fout)
>  {
>  	unsigned long long freqreg = (u64)fout *
>  				     (u64)((u64)1L << AD9832_FREQ_BITS);
> -	do_div(freqreg, mclk);
> +	freqreg = div64_ul(freqreg, mclk);
>  	return freqreg;
>  }
>  
> diff --git a/drivers/staging/iio/frequency/ad9834.c b/drivers/staging/iio/frequency/ad9834.c
> index d339d5e8e0..83d0e1360c 100644
> --- a/drivers/staging/iio/frequency/ad9834.c
> +++ b/drivers/staging/iio/frequency/ad9834.c
> @@ -10,6 +10,7 @@
>  #include <linux/workqueue.h>
>  #include <linux/device.h>
>  #include <linux/kernel.h>
> +#include <linux/math64.h>
>  #include <linux/slab.h>
>  #include <linux/sysfs.h>
>  #include <linux/list.h>
> @@ -101,7 +102,7 @@ static unsigned int ad9834_calc_freqreg(unsigned long mclk, unsigned long fout)
>  {
>  	unsigned long long freqreg = (u64)fout * (u64)BIT(AD9834_FREQ_BITS);
>  
> -	do_div(freqreg, mclk);
> +	freqreg = div64_ul(freqreg, mclk);
>  	return freqreg;
>  }
>  

Re: [PATCH] iio: frequency: ad983x: replace do_div() with div64_ul().

[Joshua Crofts]

On Thu, 9 Apr 2026 at 19:27, David Laight <david.laight.linux@gmail.com> wrote:
> Except here you have clock frequencies.
> Either they fit in 32bits or they don't.
> So the value shouldn't be 'unsigned long', but either u32 or u64.

The clk struct in linux/clk.h explicitly uses an unsigned long to represent
the clock value, which is used in this driver. Using an unsigned long
ensures platform independent usage without type mismatching.

> You need to check the domain of the values, coccinelle is just looking
> at the types.
> Even with mclk being 'unsigned long' the code is fine provided the
> frequency is below 4.2GHz.

I agree that we're not dealing with potential truncation problems, however
changing to div64_ul aligns the types with the clk API and scrubs a perfectly
valid cocci error.

-- 
Kind regards

CJD

Re: [PATCH] iio: frequency: ad983x: replace do_div() with div64_ul().

[David Laight]

On Thu, 9 Apr 2026 21:58:20 +0200
Joshua Crofts <joshua.crofts1@gmail.com> wrote:

> On Thu, 9 Apr 2026 at 19:27, David Laight <david.laight.linux@gmail.com> wrote:
> > Except here you have clock frequencies.
> > Either they fit in 32bits or they don't.
> > So the value shouldn't be 'unsigned long', but either u32 or u64.  
> 
> The clk struct in linux/clk.h explicitly uses an unsigned long to represent
> the clock value, which is used in this driver. Using an unsigned long
> ensures platform independent usage without type mismatching.

Not really.
I've NFI why the the clock API using 'unsigned long'.
It almost certainly predates 64bit and any real idea that a clock might
exceed 4.2GHz.
It might even come from someone who wrote 16bit windows code and wanted
to ensure it was actually 32bit.

For 'platform portability' clocks are limited to 32bits so the 32bit
divide is fine.
If the clock could exceed 4.2G then you'd have to use u64 throughout. 

> 
> > You need to check the domain of the values, coccinelle is just looking
> > at the types.
> > Even with mclk being 'unsigned long' the code is fine provided the
> > frequency is below 4.2GHz.  
> 
> I agree that we're not dealing with potential truncation problems, however
> changing to div64_ul aligns the types with the clk API and scrubs a perfectly
> valid cocci error.

cocci only does type checking, it doesn't know the domain of the values.
So in this case it is almost certainly a false positive.

	David