gpio: sx150x: correct and refine reset-on-probe behavior (5affb607) · Commits · 戴 / test

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:

Gregory Bean <gbean@codeaurora.org> Reviewed-by:

Jean Delvare <khali@linux-fr.org> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

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 */

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