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Commit 5affb607 authored by Gregory Bean's avatar Gregory Bean Committed by Linus Torvalds
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gpio: sx150x: correct and refine reset-on-probe behavior 



Replace the arbitrary software-reset call from the device-probe
method, because:

- It is defective.  To work correctly, it should be two byte writes,
  not a single word write.  As it stands, it does nothing.

- Some devices with sx150x expanders installed have their NRESET pins
  ganged on the same line, so resetting one causes the others to reset -
  not a nice thing to do arbitrarily!

- The probe, usually taking place at boot, implies a recent hard-reset,
  so a software reset at this point is just a waste of energy anyway.

Therefore, make it optional, defaulting to off, as this will match the
common case of probing at powerup and also matches the current broken
no-op behavior.

Signed-off-by: default avatarGregory Bean <gbean@codeaurora.org>
Reviewed-by: default avatarJean Delvare <khali@linux-fr.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0dcc48c1

drivers/gpio/sx150x.c

+21 −5
Original line number Diff line number Diff line
@@ -459,16 +459,32 @@ static int sx150x_init_io(struct sx150x_chip *chip, u8 base, u16 cfg) 
	return err;

}



static int sx150x_reset(struct sx150x_chip *chip)

{

	int err;



	err = i2c_smbus_write_byte_data(chip->client,

					chip->dev_cfg->reg_reset,

					0x12);

	if (err < 0)

		return err;



	err = i2c_smbus_write_byte_data(chip->client,

					chip->dev_cfg->reg_reset,

					0x34);

	return err;

}



static int sx150x_init_hw(struct sx150x_chip *chip,

			struct sx150x_platform_data *pdata)

{

	int err = 0;



	err = i2c_smbus_write_word_data(chip->client,

					chip->dev_cfg->reg_reset,

					0x3412);

	if (pdata->reset_during_probe) {

		err = sx150x_reset(chip);

		if (err < 0)

			return err;

	}



	err = sx150x_i2c_write(chip->client,

			chip->dev_cfg->reg_misc,

include/linux/i2c/sx150x.h

+4 −0
Original line number Diff line number Diff line
@@ -63,6 +63,9 @@ 
 *            IRQ lines will appear.  Similarly to gpio_base, the expander

 *            will create a block of irqs beginning at this number.

 *            This value is ignored if irq_summary is < 0.

 * @reset_during_probe: If set to true, the driver will trigger a full

 *                      reset of the chip at the beginning of the probe

 *                      in order to place it in a known state.

 */

struct sx150x_platform_data {

	unsigned gpio_base;
@@ -73,6 +76,7 @@ struct sx150x_platform_data { 
	u16      io_polarity;

	int      irq_summary;

	unsigned irq_base;

	bool     reset_during_probe;

};



#endif /* __LINUX_I2C_SX150X_H */