[PATCH 0/2] i2c: designware: Fixes clock issues with platform driver

[PATCH 0/2] i2c: designware: Fixes clock issues with platform driver

[Kunihiko Hayashi]

This series fixes two clock issues with i2c-designware-platdrv driver.

The first is that the clocks aren't disabled when the driver exits if
CONFIG_PM=n, the other is that the clocks aren't disabled when the probe
function fails.

Kunihiko Hayashi (2):
  i2c: designware: Fix clock issue when PM is disabled
  i2c: designware: Add disabling clocks when probe fails

 drivers/i2c/busses/i2c-designware-platdrv.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

-- 
2.34.1

[PATCH 1/2] i2c: designware: Fix clock issue when PM is disabled

[Kunihiko Hayashi]

When removing the driver, enable the clocks once by calling
pm_runtime_get_sync(), and call pm_runtime_put_sync() to disable
the clocks.

If CONFIG_PM=y, clocks for this controller are disabled when it's in
the idle state. So the clocks are properly disabled when the driver
exits.

Othewise, the clocks are always enabled and the PM functions have
no effect. Therefore, the driver exits without disabling the clocks.

    # cat /sys/kernel/debug/clk/clk-pclk/clk_enable_count
    18
    # echo 1214a000.i2c > /sys/bus/platform/drivers/i2c_designware/bind
    # cat /sys/kernel/debug/clk/clk-pclk/clk_enable_count
    20
    # echo 1214a000.i2c > /sys/bus/platform/drivers/i2c_designware/unbind
    # cat /sys/kernel/debug/clk/clk-pclk/clk_enable_count
    20

To ensure that the clocks can be disabled correctly even without
CONFIG_PM=y, should add the following fixes:

- Replace with pm_runtime_put_noidle(), which only decrements the clock
  count.
- Call i2c_dw_prepare_clk(false) to explicitly disable the clocks.

Fixes: 7272194ed391f ("i2c-designware: add minimal support for runtime PM")
Co-developed-by: Kohei Ito <ito.kohei@socionext.com>
Signed-off-by: Kohei Ito <ito.kohei@socionext.com>
Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
---
 drivers/i2c/busses/i2c-designware-platdrv.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index d6e1ee935399..edaebfb165f9 100644
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -325,9 +325,11 @@ static void dw_i2c_plat_remove(struct platform_device *pdev)
 	i2c_dw_disable(dev);
 
 	pm_runtime_dont_use_autosuspend(device);
-	pm_runtime_put_sync(device);
+	pm_runtime_put_noidle(device);
 	dw_i2c_plat_pm_cleanup(dev);
 
+	i2c_dw_prepare_clk(dev, false);
+
 	i2c_dw_remove_lock_support(dev);
 
 	reset_control_assert(dev->rst);
-- 
2.34.1

Re: [PATCH 1/2] i2c: designware: Fix clock issue when PM is disabled

[Kunihiko Hayashi]

On 2025/07/24 11:13, Kunihiko Hayashi wrote:
> When removing the driver, enable the clocks once by calling
> pm_runtime_get_sync(), and call pm_runtime_put_sync() to disable
> the clocks.
> 
> If CONFIG_PM=y, clocks for this controller are disabled when it's in
> the idle state. So the clocks are properly disabled when the driver
> exits.
> 
> Othewise, the clocks are always enabled and the PM functions have
> no effect. Therefore, the driver exits without disabling the clocks.
> 
>      # cat /sys/kernel/debug/clk/clk-pclk/clk_enable_count
>      18
>      # echo 1214a000.i2c > /sys/bus/platform/drivers/i2c_designware/bind
>      # cat /sys/kernel/debug/clk/clk-pclk/clk_enable_count
>      20
>      # echo 1214a000.i2c > /sys/bus/platform/drivers/i2c_designware/unbind
>      # cat /sys/kernel/debug/clk/clk-pclk/clk_enable_count
>      20
> 
> To ensure that the clocks can be disabled correctly even without
> CONFIG_PM=y, should add the following fixes:
> 
> - Replace with pm_runtime_put_noidle(), which only decrements the clock
>    count.

This description is wrong.
The pm_runtime_put_noidle() decrements the runtime PM usage count.

> - Call i2c_dw_prepare_clk(false) to explicitly disable the clocks.

This decrements the clock count.

I'll fix it and resend as v2.

Thanks,

---
Best Regards
Kunihiko Hayashi

[PATCH 2/2] i2c: designware: Add disabling clocks when probe fails

[Kunihiko Hayashi]

After an error occurs during probing state, dw_i2c_plat_pm_cleanup() is
called. However, this function doesn't disable clocks and the clock-enable
count keeps increasing. Should disable these clocks explicitly.

Co-developed-by: Kohei Ito <ito.kohei@socionext.com>
Signed-off-by: Kohei Ito <ito.kohei@socionext.com>
Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
---
 drivers/i2c/busses/i2c-designware-platdrv.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index edaebfb165f9..f6424dcfdff6 100644
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -308,6 +308,7 @@ static int dw_i2c_plat_probe(struct platform_device *pdev)
 
 exit_probe:
 	dw_i2c_plat_pm_cleanup(dev);
+	i2c_dw_prepare_clk(dev, false);
 exit_reset:
 	reset_control_assert(dev->rst);
 	return ret;
-- 
2.34.1