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gpio: sx150x: correct and refine reset-on-probe behavior

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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 <[email protected]>
Reviewed-by: Jean Delvare <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Gregory Bean 2010-09-09 16:38:02 -07:00 • committed by Linus Torvalds
commit 5affb60772
2 changed files with 25 additions and 5 deletions
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26
drivers/gpio/sx150x.c
View file

@ -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 (err < 0)
return err;
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,