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media: i2c: Add note to prevent buggy code re-use

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adv7604 and et8ek8 sensor drivers have mixed up logical and line level
for reset/powerdown signal.  They call it a reset signal (it indeed
behaves like that), but drivers assert the reset to operate which is
clearly incorrect and relies on wrong ACTIVE_HIGH flag in the DTS.

People in discussions copy existing poor code and claim they can repeat
same mistake, so add a note to prevent that.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>
This commit is contained in:
Krzysztof Kozlowski 2025-12-30 09:34:36 +01:00 • committed by Hans Verkuil
parent 2f130245f2
commit 5152437f76
2 changed files with 11 additions and 1 deletions
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8
drivers/media/i2c/adv7604.c
View file

@ -3453,7 +3453,13 @@ static int configure_regmaps(struct adv76xx_state *state)
static void adv76xx_reset(struct adv76xx_state *state)
{
if (state->reset_gpio) {
/* ADV76XX can be reset by a low reset pulse of minimum 5 ms. */
/*
* Note: Misinterpretation of reset assertion - do not re-use
* this code. The reset pin is using incorrect (for a reset
* signal) logical level.
*
* ADV76XX can be reset by a low reset pulse of minimum 5 ms.
*/
gpiod_set_value_cansleep(state->reset_gpio, 0);
usleep_range(5000, 10000);
gpiod_set_value_cansleep(state->reset_gpio, 1);

4
drivers/media/i2c/et8ek8/et8ek8_driver.c
View file

@ -835,6 +835,10 @@ static int et8ek8_power_on(struct et8ek8_sensor *sensor)
udelay(10); /* I wish this is a good value */
/*
* Note: Misinterpretation of reset assertion - do not re-use this code.
* The reset pin is using incorrect (for a reset signal) logical level.
*/
gpiod_set_value(sensor->reset, 1);
msleep(5000 * 1000 / sensor->xclk_freq + 1); /* Wait 5000 cycles */