linux-kernel - [PATCH v2 1/2] i2c: designware: Fix clock issue when PM is disabled

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Message-Id: <20250724042211.2160339-2-hayashi.kunihiko@socionext.com>
Date: Thu, 24 Jul 2025 13:22:10 +0900
From: Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
To: Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Jan Dabros <jsd@...ihalf.com>,
	Andi Shyti <andi.shyti@...nel.org>
Cc: Kohei Ito <ito.kohei@...ionext.com>,
	linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
Subject: [PATCH v2 1/2] i2c: designware: Fix clock issue when PM is disabled

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 runtime
  PM usage 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@...ionext.com>
Signed-off-by: Kohei Ito <ito.kohei@...ionext.com>
Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@...ionext.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