[PATCH v1 0/7] i2c: busses: Introduce and use HZ_PER_GHZ

[PATCH v1 0/7] i2c: busses: Introduce and use HZ_PER_GHZ

[Andy Shevchenko]

A few drivers for I²C host controllers use HZ_PER_GHZ in numeric form.
This is less readable and prone to subtle mistakes. Instead, introduce
a well defined constant and use it in the drivers. No functional change
implied except one case where 64-bit division replaced with 32-bit one.

Andy Shevchenko (7):
  units: Add HZ_PER_GHZ
  i2c: mlxbf: Use HZ_PER_GHZ constant instead of custom one
  i2c: mt65xx: Use HZ_PER_GHZ constant instead of plain number
  i2c: nomadik: Use HZ_PER_GHZ constant instead of plain number
  i2c: rk3x: Use HZ_PER_GHZ constant instead of plain number
  i2c: st: Use HZ_PER_GHZ constant instead of plain number
  i2c: synquacer: Use HZ_PER_GHZ constant instead of plain number

 drivers/i2c/busses/i2c-mlxbf.c     |  5 ++---
 drivers/i2c/busses/i2c-mt65xx.c    | 11 ++++++-----
 drivers/i2c/busses/i2c-nomadik.c   |  7 ++++---
 drivers/i2c/busses/i2c-rk3x.c      | 12 ++++++------
 drivers/i2c/busses/i2c-st.c        |  3 ++-
 drivers/i2c/busses/i2c-synquacer.c |  3 ++-
 include/linux/units.h              |  3 +++
 7 files changed, 25 insertions(+), 19 deletions(-)

-- 
2.50.1

[PATCH v1 1/7] units: Add HZ_PER_GHZ

[Andy Shevchenko]

The is going to be a new user of the HZ_PER_GHZ definition besides
possibly existing ones. Add that one to the header.

While at it, split Hz and kHz groups of the multipliers for better
maintenance and readability.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 include/linux/units.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/linux/units.h b/include/linux/units.h
index 00e15de33eca..0c296a004e89 100644
--- a/include/linux/units.h
+++ b/include/linux/units.h
@@ -25,9 +25,12 @@
 #define MICROHZ_PER_HZ		1000000UL
 #define MILLIHZ_PER_HZ		1000UL
 
+/* Hz based multipliers */
 #define HZ_PER_KHZ		1000UL
 #define HZ_PER_MHZ		1000000UL
+#define HZ_PER_GHZ		1000000000UL
 
+/* kHz based multipliers */
 #define KHZ_PER_MHZ		1000UL
 #define KHZ_PER_GHZ		1000000UL
 
-- 
2.50.1

[PATCH v1 2/7] i2c: mlxbf: Use HZ_PER_GHZ constant instead of custom one

[Andy Shevchenko]

Use HZ_PER_GHZ constant instead of custom one. No functional changes.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/i2c/busses/i2c-mlxbf.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/i2c/busses/i2c-mlxbf.c b/drivers/i2c/busses/i2c-mlxbf.c
index 8345f7e6385d..746f65989138 100644
--- a/drivers/i2c/busses/i2c-mlxbf.c
+++ b/drivers/i2c/busses/i2c-mlxbf.c
@@ -20,6 +20,7 @@
 #include <linux/platform_device.h>
 #include <linux/string.h>
 #include <linux/string_choices.h>
+#include <linux/units.h>
 
 /* Defines what functionality is present. */
 #define MLXBF_I2C_FUNC_SMBUS_BLOCK \
@@ -72,8 +73,6 @@
 /* Constant used to determine the PLL frequency. */
 #define MLNXBF_I2C_COREPLL_CONST    16384ULL
 
-#define MLXBF_I2C_FREQUENCY_1GHZ  1000000000ULL
-
 /* PLL registers. */
 #define MLXBF_I2C_CORE_PLL_REG1         0x4
 #define MLXBF_I2C_CORE_PLL_REG2         0x8
@@ -1083,7 +1082,7 @@ static u32 mlxbf_i2c_get_ticks(struct mlxbf_i2c_priv *priv, u64 nanoseconds,
 	 *         Frequency
 	 */
 	frequency = priv->frequency;
-	ticks = div_u64(nanoseconds * frequency, MLXBF_I2C_FREQUENCY_1GHZ);
+	ticks = div_u64(nanoseconds * frequency, HZ_PER_GHZ);
 	/*
 	 * The number of ticks is rounded down and if minimum is equal to 1
 	 * then add one tick.
-- 
2.50.1

[PATCH v1 3/7] i2c: mt65xx: Use HZ_PER_GHZ constant instead of plain number

[Andy Shevchenko]

Use defined constant to avoid the possible mistakes and to provide
an additional information on the units.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/i2c/busses/i2c-mt65xx.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/i2c/busses/i2c-mt65xx.c b/drivers/i2c/busses/i2c-mt65xx.c
index aefdbee1f03c..cb4d3aa709d0 100644
--- a/drivers/i2c/busses/i2c-mt65xx.c
+++ b/drivers/i2c/busses/i2c-mt65xx.c
@@ -24,6 +24,7 @@
 #include <linux/scatterlist.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
+#include <linux/units.h>
 
 #define I2C_RS_TRANSFER			(1 << 4)
 #define I2C_ARB_LOST			(1 << 3)
@@ -685,7 +686,7 @@ static int mtk_i2c_get_clk_div_restri(struct mtk_i2c *i2c,
  * Check and Calculate i2c ac-timing
  *
  * Hardware design:
- * sample_ns = (1000000000 * (sample_cnt + 1)) / clk_src
+ * sample_ns = (HZ_PER_GHZ * (sample_cnt + 1)) / clk_src
  * xxx_cnt_div =  spec->min_xxx_ns / sample_ns
  *
  * Sample_ns is rounded down for xxx_cnt_div would be greater
@@ -701,9 +702,8 @@ static int mtk_i2c_check_ac_timing(struct mtk_i2c *i2c,
 {
 	const struct i2c_spec_values *spec;
 	unsigned int su_sta_cnt, low_cnt, high_cnt, max_step_cnt;
-	unsigned int sda_max, sda_min, clk_ns, max_sta_cnt = 0x3f;
-	unsigned int sample_ns = div_u64(1000000000ULL * (sample_cnt + 1),
-					 clk_src);
+	unsigned int sda_max, sda_min, max_sta_cnt = 0x3f;
+	unsigned int clk_ns, sample_ns;
 
 	if (!i2c->dev_comp->timing_adjust)
 		return 0;
@@ -713,8 +713,9 @@ static int mtk_i2c_check_ac_timing(struct mtk_i2c *i2c,
 
 	spec = mtk_i2c_get_spec(check_speed);
 
+	sample_ns = div_u64(1ULL * HZ_PER_GHZ * (sample_cnt + 1), clk_src);
 	if (i2c->dev_comp->ltiming_adjust)
-		clk_ns = 1000000000 / clk_src;
+		clk_ns = HZ_PER_GHZ / clk_src;
 	else
 		clk_ns = sample_ns / 2;
 
-- 
2.50.1

[PATCH v1 4/7] i2c: nomadik: Use HZ_PER_GHZ constant instead of plain number

[Andy Shevchenko]

Use defined constant to avoid the possible mistakes and to provide
an additional information on the units.

While at it, drop unneeded 64-bit division, all operands fit 32-bit.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/i2c/busses/i2c-nomadik.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/i2c/busses/i2c-nomadik.c b/drivers/i2c/busses/i2c-nomadik.c
index 19b648fc094d..b63ee51c1652 100644
--- a/drivers/i2c/busses/i2c-nomadik.c
+++ b/drivers/i2c/busses/i2c-nomadik.c
@@ -31,6 +31,7 @@
 #include <linux/pm_runtime.h>
 #include <linux/regmap.h>
 #include <linux/slab.h>
+#include <linux/units.h>
 
 #define DRIVER_NAME "nmk-i2c"
 
@@ -419,10 +420,10 @@ static void setup_i2c_controller(struct nmk_i2c_dev *priv)
 	 * modes are 250ns, 100ns, 10ns respectively.
 	 *
 	 * As the time for one cycle T in nanoseconds is
-	 * T = (1/f) * 1000000000 =>
-	 * slsu = cycles / (1000000000 / f) + 1
+	 * T = (1/f) * HZ_PER_GHZ =>
+	 * slsu = cycles / (HZ_PER_GHZ / f) + 1
 	 */
-	ns = DIV_ROUND_UP_ULL(1000000000ULL, i2c_clk);
+	ns = DIV_ROUND_UP(HZ_PER_GHZ, i2c_clk);
 	switch (priv->sm) {
 	case I2C_FREQ_MODE_FAST:
 	case I2C_FREQ_MODE_FAST_PLUS:
-- 
2.50.1

[PATCH v1 5/7] i2c: rk3x: Use HZ_PER_GHZ constant instead of plain number

[Andy Shevchenko]

Use defined constant to avoid the possible mistakes and to provide
an additional information on the units.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/i2c/busses/i2c-rk3x.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/i2c/busses/i2c-rk3x.c b/drivers/i2c/busses/i2c-rk3x.c
index d4e9196445c0..fcede9f6ed54 100644
--- a/drivers/i2c/busses/i2c-rk3x.c
+++ b/drivers/i2c/busses/i2c-rk3x.c
@@ -19,6 +19,7 @@
 #include <linux/of_irq.h>
 #include <linux/spinlock.h>
 #include <linux/clk.h>
+#include <linux/units.h>
 #include <linux/wait.h>
 #include <linux/mfd/syscon.h>
 #include <linux/regmap.h>
@@ -896,13 +897,12 @@ static void rk3x_i2c_adapt_div(struct rk3x_i2c *i2c, unsigned long clk_rate)
 
 	clk_disable(i2c->pclk);
 
-	t_low_ns = div_u64(((u64)calc.div_low + 1) * 8 * 1000000000, clk_rate);
-	t_high_ns = div_u64(((u64)calc.div_high + 1) * 8 * 1000000000,
-			    clk_rate);
+	t_low_ns = div_u64(8ULL * HZ_PER_GHZ * (calc.div_low + 1), clk_rate);
+	t_high_ns = div_u64(8ULL * HZ_PER_GHZ * (calc.div_high + 1), clk_rate);
 	dev_dbg(i2c->dev,
-		"CLK %lukhz, Req %uns, Act low %lluns high %lluns\n",
-		clk_rate / 1000,
-		1000000000 / t->bus_freq_hz,
+		"CLK %lukHz, Req %luns, Act low %lluns high %lluns\n",
+		clk_rate / HZ_PER_KHZ,
+		HZ_PER_GHZ / t->bus_freq_hz,
 		t_low_ns, t_high_ns);
 }
 
-- 
2.50.1

[PATCH v1 6/7] i2c: st: Use HZ_PER_GHZ constant instead of plain number

[Andy Shevchenko]

Use defined constant to avoid the possible mistakes and to provide
an additional information on the units.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/i2c/busses/i2c-st.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-st.c b/drivers/i2c/busses/i2c-st.c
index 97d70e667227..751ea421caaf 100644
--- a/drivers/i2c/busses/i2c-st.c
+++ b/drivers/i2c/busses/i2c-st.c
@@ -20,6 +20,7 @@
 #include <linux/of.h>
 #include <linux/pinctrl/consumer.h>
 #include <linux/platform_device.h>
+#include <linux/units.h>
 
 /* SSC registers */
 #define SSC_BRG				0x000
@@ -285,7 +286,7 @@ static void st_i2c_hw_config(struct st_i2c_dev *i2c_dev)
 	writel_relaxed(val, i2c_dev->base + SSC_CTL);
 
 	rate = clk_get_rate(i2c_dev->clk);
-	ns_per_clk = 1000000000 / rate;
+	ns_per_clk = HZ_PER_GHZ / rate;
 
 	/* Baudrate */
 	val = rate / (2 * t->rate);
-- 
2.50.1

[PATCH v1 7/7] i2c: synquacer: Use HZ_PER_GHZ constant instead of plain number

[Andy Shevchenko]

Use defined constant to avoid the possible mistakes and to provide
an additional information on the units.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/i2c/busses/i2c-synquacer.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-synquacer.c b/drivers/i2c/busses/i2c-synquacer.c
index 1230f51e1624..4891d68bf0ee 100644
--- a/drivers/i2c/busses/i2c-synquacer.c
+++ b/drivers/i2c/busses/i2c-synquacer.c
@@ -18,9 +18,10 @@
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
+#include <linux/units.h>
 
 #define WAIT_PCLK(n, rate)	\
-	ndelay(DIV_ROUND_UP(DIV_ROUND_UP(1000000000, rate), n) + 10)
+	ndelay(DIV_ROUND_UP(DIV_ROUND_UP(HZ_PER_GHZ, rate), n) + 10)
 
 /* I2C register address definitions */
 #define SYNQUACER_I2C_REG_BSR		(0x00 << 2) // Bus Status
-- 
2.50.1

Re: [PATCH v1 1/7] units: Add HZ_PER_GHZ

[Linus Walleij]

On Mon, Jan 12, 2026 at 2:49 PM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:

> The is going to be a new user of the HZ_PER_GHZ definition besides
> possibly existing ones. Add that one to the header.
>
> While at it, split Hz and kHz groups of the multipliers for better
> maintenance and readability.
>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

This looks right to me:
Reviewed-by: Linus Walleij <linusw@kernel.org>

Yours,
Linus Walleij

Re: [PATCH v1 4/7] i2c: nomadik: Use HZ_PER_GHZ constant instead of plain number

[Linus Walleij]

On Mon, Jan 12, 2026 at 2:49 PM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:

> Use defined constant to avoid the possible mistakes and to provide
> an additional information on the units.
>
> While at it, drop unneeded 64-bit division, all operands fit 32-bit.
>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

It makes perfect sense, I don't remember why I put ULL in there
anymore :/

Reviewed-by: Linus Walleij <linusw@kernel.org>

Yours,
Linus Walleij

Re: [PATCH v1 0/7] i2c: busses: Introduce and use HZ_PER_GHZ

[AngeloGioacchino Del Regno]

Il 12/01/26 14:46, Andy Shevchenko ha scritto:
> A few drivers for I²C host controllers use HZ_PER_GHZ in numeric form.
> This is less readable and prone to subtle mistakes. Instead, introduce
> a well defined constant and use it in the drivers. No functional change
> implied except one case where 64-bit division replaced with 32-bit one.
> 
> Andy Shevchenko (7):
>    units: Add HZ_PER_GHZ
>    i2c: mlxbf: Use HZ_PER_GHZ constant instead of custom one
>    i2c: mt65xx: Use HZ_PER_GHZ constant instead of plain number
>    i2c: nomadik: Use HZ_PER_GHZ constant instead of plain number
>    i2c: rk3x: Use HZ_PER_GHZ constant instead of plain number
>    i2c: st: Use HZ_PER_GHZ constant instead of plain number
>    i2c: synquacer: Use HZ_PER_GHZ constant instead of plain number
> 
>   drivers/i2c/busses/i2c-mlxbf.c     |  5 ++---
>   drivers/i2c/busses/i2c-mt65xx.c    | 11 ++++++-----
>   drivers/i2c/busses/i2c-nomadik.c   |  7 ++++---
>   drivers/i2c/busses/i2c-rk3x.c      | 12 ++++++------
>   drivers/i2c/busses/i2c-st.c        |  3 ++-
>   drivers/i2c/busses/i2c-synquacer.c |  3 ++-
>   include/linux/units.h              |  3 +++
>   7 files changed, 25 insertions(+), 19 deletions(-)
> 

Whole series is

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

Re: [PATCH v1 1/7] units: Add HZ_PER_GHZ

[Andi Shyti]

Hi Andy,

On Mon, Jan 12, 2026 at 02:46:09PM +0100, Andy Shevchenko wrote:
> The is going to be a new user of the HZ_PER_GHZ definition besides
> possibly existing ones. Add that one to the header.
> 
> While at it, split Hz and kHz groups of the multipliers for better
> maintenance and readability.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

Reviewed-by: Andi Shyti <andi.shyti@kernel.org>

I'm taking this via i2c if no one is against.

Andi

Re: [PATCH v1 5/7] i2c: rk3x: Use HZ_PER_GHZ constant instead of plain number

[Heiko Stübner]

Am Montag, 12. Januar 2026, 14:46:13 Mitteleuropäische Normalzeit schrieb Andy Shevchenko:
> Use defined constant to avoid the possible mistakes and to provide
> an additional information on the units.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

Reviewed-by: Heiko Stuebner <heiko@sntech.de>

Re: [PATCH v1 0/7] i2c: busses: Introduce and use HZ_PER_GHZ

[Wolfram Sang]

On Mon, Jan 12, 2026 at 02:46:08PM +0100, Andy Shevchenko wrote:
> A few drivers for I²C host controllers use HZ_PER_GHZ in numeric form.
> This is less readable and prone to subtle mistakes. Instead, introduce
> a well defined constant and use it in the drivers. No functional change
> implied except one case where 64-bit division replaced with 32-bit one.
> 
> Andy Shevchenko (7):
>   units: Add HZ_PER_GHZ
>   i2c: mlxbf: Use HZ_PER_GHZ constant instead of custom one
>   i2c: mt65xx: Use HZ_PER_GHZ constant instead of plain number
>   i2c: nomadik: Use HZ_PER_GHZ constant instead of plain number
>   i2c: rk3x: Use HZ_PER_GHZ constant instead of plain number
>   i2c: st: Use HZ_PER_GHZ constant instead of plain number
>   i2c: synquacer: Use HZ_PER_GHZ constant instead of plain number
> 

Fine with me:

Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>

Re: [PATCH v1 6/7] i2c: st: Use HZ_PER_GHZ constant instead of plain number

[Patrice CHOTARD]

On 1/12/26 14:46, Andy Shevchenko wrote:
> Use defined constant to avoid the possible mistakes and to provide
> an additional information on the units.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
>  drivers/i2c/busses/i2c-st.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/busses/i2c-st.c b/drivers/i2c/busses/i2c-st.c
> index 97d70e667227..751ea421caaf 100644
> --- a/drivers/i2c/busses/i2c-st.c
> +++ b/drivers/i2c/busses/i2c-st.c
> @@ -20,6 +20,7 @@
>  #include <linux/of.h>
>  #include <linux/pinctrl/consumer.h>
>  #include <linux/platform_device.h>
> +#include <linux/units.h>
>  
>  /* SSC registers */
>  #define SSC_BRG				0x000
> @@ -285,7 +286,7 @@ static void st_i2c_hw_config(struct st_i2c_dev *i2c_dev)
>  	writel_relaxed(val, i2c_dev->base + SSC_CTL);
>  
>  	rate = clk_get_rate(i2c_dev->clk);
> -	ns_per_clk = 1000000000 / rate;
> +	ns_per_clk = HZ_PER_GHZ / rate;
>  
>  	/* Baudrate */
>  	val = rate / (2 * t->rate);

Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>

Thanks
Patrice

Re: [PATCH v1 0/7] i2c: busses: Introduce and use HZ_PER_GHZ

[Andi Shyti]

Hi Andy,

> Andy Shevchenko (7):
>   units: Add HZ_PER_GHZ
>   i2c: mlxbf: Use HZ_PER_GHZ constant instead of custom one
>   i2c: mt65xx: Use HZ_PER_GHZ constant instead of plain number
>   i2c: nomadik: Use HZ_PER_GHZ constant instead of plain number
>   i2c: rk3x: Use HZ_PER_GHZ constant instead of plain number
>   i2c: st: Use HZ_PER_GHZ constant instead of plain number
>   i2c: synquacer: Use HZ_PER_GHZ constant instead of plain number

merged to i2c/i2c-host.

Thanks,
Andi

Re: [PATCH v1 0/7] i2c: busses: Introduce and use HZ_PER_GHZ

[Andy Shevchenko]

On Wed, Jan 14, 2026 at 08:36:09AM +0100, Andi Shyti wrote:
> > Andy Shevchenko (7):
> >   units: Add HZ_PER_GHZ
> >   i2c: mlxbf: Use HZ_PER_GHZ constant instead of custom one
> >   i2c: mt65xx: Use HZ_PER_GHZ constant instead of plain number
> >   i2c: nomadik: Use HZ_PER_GHZ constant instead of plain number
> >   i2c: rk3x: Use HZ_PER_GHZ constant instead of plain number
> >   i2c: st: Use HZ_PER_GHZ constant instead of plain number
> >   i2c: synquacer: Use HZ_PER_GHZ constant instead of plain number
> 
> merged to i2c/i2c-host.

Thank you!

-- 
With Best Regards,
Andy Shevchenko