Some module manufacturers [1][2] don't expose the RESETB and PWDN pins of the sensor directly through the 15-pin FFC connector. Instead wiring ~PWDN gpio to the sensor pins with appropriate delays. In such cases, reset_gpio will not be available to the driver, but it will still be toggled when the sensor is powered on, and thus we should still honor the wait time of >= 5ms + 1ms + 20ms (see figure 2-3 in [3]) before attempting any i/o operations over SCCB. Also, rename the function to ov5640_powerup_sequence to better match the datasheet (section 2.7). [1] https://digilent.com/reference/_media/reference/add-ons/pcam-5c/pcam_5c_sch.pdf [2] https://www.alinx.com/public/upload/file/AN5641_User_Manual.pdf [3] https://cdn.sparkfun.com/datasheets/Sensors/LightImaging/OV5640_datasheet.pdf Fixes: 19a81c1426c1 ("[media] add Omnivision OV5640 sensor driver") Signed-off-by: Jai Luthra <j-luthra@xxxxxx> --- drivers/media/i2c/ov5640.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-) diff --git a/drivers/media/i2c/ov5640.c b/drivers/media/i2c/ov5640.c index a9cd21c49147..41e4a4f1b99d 100644 --- a/drivers/media/i2c/ov5640.c +++ b/drivers/media/i2c/ov5640.c @@ -2372,11 +2372,22 @@ static void ov5640_power(struct ov5640_dev *sensor, bool enable) gpiod_set_value_cansleep(sensor->pwdn_gpio, enable ? 0 : 1); } -static void ov5640_reset(struct ov5640_dev *sensor) +/* + * From section 2.7 power up sequence: + * t0 + t1 + t2 >= 5ms Delay from DOVDD stable to PWDN pull down + * t3 >= 1ms Delay from PWDN pull down to RESETB pull up + * t4 >= 20ms Delay from RESETB pull up to SCCB (i2c) stable + * + * Some modules don't expose RESETB/PWDN pins directly, instead providing a + * "PWUP" GPIO which is wired through appropriate delays and inverters to the + * pins. + * + * In such cases, this gpio should be mapped to pwdn_gpio in the driver, and we + * should still toggle the pwdn_gpio below with the appropriate delays, while + * the calls to reset_gpio will be ignored. + */ +static void ov5640_powerup_sequence(struct ov5640_dev *sensor) { - if (!sensor->reset_gpio) - return; - gpiod_set_value_cansleep(sensor->reset_gpio, 0); /* camera power cycle */ @@ -2412,8 +2423,7 @@ static int ov5640_set_power_on(struct ov5640_dev *sensor) goto xclk_off; } - ov5640_reset(sensor); - ov5640_power(sensor, true); + ov5640_powerup_sequence(sensor); ret = ov5640_init_slave_id(sensor); if (ret) -- 2.17.1
