i2c: mediatek: add bus regulator control for power saving

Add conditional bus regulator enable/disable in mtk_i2c_transfer()
to support I2C bus power gating for platforms that require it.

This implementation:
- Enables bus_regulator before clk_bulk_enable() if vbus-supply is defined
- Disables bus_regulator after clk_bulk_disable()
- Only activates when vbus-supply is provided in device tree
- Has no impact on platforms without vbus-supply defined

This approach provides power savings for platforms with an extra I2C bus
regulator, while avoiding runtime PM complexity.

Tested on MT8188.

Signed-off-by: Adlavinitha Reddy <adlavinitha.reddy@mediatek.com>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Link: https://lore.kernel.org/r/20260318084621.4127757-2-adlavinitha.reddy@mediatek.com

diff --git a/drivers/i2c/busses/i2c-mt65xx.c b/drivers/i2c/busses/i2c-mt65xx.c
index cb4d3aa709d010d24a9ce1894e089134c11d8bda..126040ca05f1470f0e003d25f4c6d65a3a52790f 100644 (file)
--- a/drivers/i2c/busses/i2c-mt65xx.c
+++ b/drivers/i2c/busses/i2c-mt65xx.c
@@ -21,6 +21,7 @@
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
 #include <linux/scatterlist.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
@@ -1244,9 +1245,15 @@ static int mtk_i2c_transfer(struct i2c_adapter *adap,
        bool write_then_read_en = false;
        struct mtk_i2c *i2c = i2c_get_adapdata(adap);
 
+       if (i2c->adap.bus_regulator) {
+               ret = regulator_enable(i2c->adap.bus_regulator);
+               if (ret)
+                       return ret;
+       }
+
        ret = clk_bulk_enable(I2C_MT65XX_CLK_MAX, i2c->clocks);
        if (ret)
-               return ret;
+               goto err_regulator;
 
        i2c->auto_restart = i2c->dev_comp->auto_restart;
 
@@ -1301,6 +1308,10 @@ static int mtk_i2c_transfer(struct i2c_adapter *adap,
 
 err_exit:
        clk_bulk_disable(I2C_MT65XX_CLK_MAX, i2c->clocks);
+err_regulator:
+       if (i2c->adap.bus_regulator)
+               regulator_disable(i2c->adap.bus_regulator);
+
        return ret;
 }