| Message ID | 20250220-pca976x-reset-driver-v1-2-6abbf043050e@cherry.de |
|---|---|
| State | New |
| Headers | show |
| Series | gpio: pcf857x: add support for reset-gpios on (most) PCA967x | expand |
On Thu, Feb 20, 2025 at 01:13:06PM +0100, Quentin Schulz wrote: > On 2/20/25 11:52 AM, Heiko Stübner wrote: > > Am Donnerstag, 20. Februar 2025, 10:56:52 MEZ schrieb Quentin Schulz: > >> From: Quentin Schulz <quentin.schulz@cherry.de> > >> > >> The PCA9670, PCA9671, PCA9672 and PCA9673 all have a RESETN input pin > >> that is used to reset the I2C GPIO expander. > >> > >> One needs to hold this pin low for at least 4us and the reset should be > >> finished after about 100us according to the datasheet[1]. Once the reset > >> is done, the "registers and I2C-bus state machine will be held in their > >> default state until the RESET input is once again HIGH.". > >> > >> Because the logic is reset, the latch values eventually provided in the > >> Device Tree via lines-initial-states property are inapplicable so they > >> are simply ignored if a reset GPIO is provided. > >> > >> [1] https://www.nxp.com/docs/en/data-sheet/PCA9670.pdf 8.5 and fig 22. > >> Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de> > >> --- > >> drivers/gpio/gpio-pcf857x.c | 29 ++++++++++++++++++++++++++--- > >> 1 file changed, 26 insertions(+), 3 deletions(-) > >> > >> diff --git a/drivers/gpio/gpio-pcf857x.c b/drivers/gpio/gpio-pcf857x.c > >> index 7c57eaeb0afeba8953d998d8eec60a65b40efb6d..94077208e24ae99a1e8762e783f0eabc580fa520 100644 > >> --- a/drivers/gpio/gpio-pcf857x.c > >> +++ b/drivers/gpio/gpio-pcf857x.c > >> @@ -5,6 +5,7 @@ > >> * Copyright (C) 2007 David Brownell > >> */ > >> > >> +#include <linux/delay.h> > >> #include <linux/gpio/driver.h> > >> #include <linux/i2c.h> > >> #include <linux/interrupt.h> > > > > this is missing > > #include <linux/gpio/consumer.h> > > > > because otherwise you end up with > > ../drivers/gpio/gpio-pcf857x.c: In function ‘pcf857x_probe’: > > ../drivers/gpio/gpio-pcf857x.c:300:21: error: implicit declaration of function ‘devm_gpiod_get_optional’; did you mean ‘devm_regulator_get_optional’? [-Wimplicit-function-declaration] > > 300 | rstn_gpio = devm_gpiod_get_optional(&client->dev, "reset", GPIOD_OUT_HIGH); > > | ^~~~~~~~~~~~~~~~~~~~~~~ > > | devm_regulator_get_optional > > ../drivers/gpio/gpio-pcf857x.c:300:68: error: ‘GPIOD_OUT_HIGH’ undeclared (first use in this function) > > 300 | rstn_gpio = devm_gpiod_get_optional(&client->dev, "reset", GPIOD_OUT_HIGH); > > | ^~~~~~~~~~~~~~ > > ../drivers/gpio/gpio-pcf857x.c:300:68: note: each undeclared identifier is reported only once for each function it appears in > > ../drivers/gpio/gpio-pcf857x.c:309:17: error: implicit declaration of function ‘gpiod_set_value’ [-Wimplicit-function-declaration] > > 309 | gpiod_set_value(rstn_gpio, 0); > > | ^~~~~~~~~~~~~~~ > > > > It compiles just fine on my end, this is all very suspicious. > > GPIO_PCF857X symbol depends on GPIOLIB which builds this function. > > Now, I have no clue how it finds the declaration for me without this > include. Any clue? Possibly indirect includes that depend on your kernel config ? The above functions and macros are declared and defined in linux/gpio/consumer.h, so you should include it regardless. > >> @@ -272,12 +273,11 @@ static const struct irq_chip pcf857x_irq_chip = { > >> > >> static int pcf857x_probe(struct i2c_client *client) > >> { > >> + struct gpio_desc *rstn_gpio; I'd call it reset_gpio as in drivers we deal with logical signals. Up to you. > >> struct pcf857x *gpio; > >> - unsigned int n_latch = 0; > >> + unsigned int n_latch; > >> int status; > >> > >> - device_property_read_u32(&client->dev, "lines-initial-states", &n_latch); > >> - > >> /* Allocate, initialize, and register this gpio_chip. */ > >> gpio = devm_kzalloc(&client->dev, sizeof(*gpio), GFP_KERNEL); > >> if (!gpio) > >> @@ -297,6 +297,29 @@ static int pcf857x_probe(struct i2c_client *client) > >> gpio->chip.direction_output = pcf857x_output; > >> gpio->chip.ngpio = (uintptr_t)i2c_get_match_data(client); > >> > >> + rstn_gpio = devm_gpiod_get_optional(&client->dev, "reset", GPIOD_OUT_HIGH); > >> + if (IS_ERR(rstn_gpio)) { > >> + return dev_err_probe(&client->dev, PTR_ERR(rstn_gpio), > >> + "failed to get reset GPIO\n"); > >> + } No need for curly braces. > >> + > >> + if (rstn_gpio) { > >> + /* Reset already held with devm_gpiod_get_optional with GPIOD_OUT_HIGH */ > >> + usleep_range(4, 8); /* tw(rst) > 4us */ > >> + gpiod_set_value(rstn_gpio, 0); > >> + usleep_range(100, 200); /* trst > 100uS */ Maybe use fsleep() for both ? > >> + > >> + /* > >> + * Reset "will initialize to their default states of all I/Os to > >> + * inputs with weak current source to VDD", which is the same as > >> + * writing 1 for all I/Os which is 0 in n_latch. > >> + */ > >> + n_latch = 0; > >> + } else { > >> + device_property_read_u32(&client->dev, "lines-initial-states", > >> + &n_latch); > > > > device_property_read_u32 will not fill n_latch if the property is missing. > > Before n_latch was always set to 0 at the declaration point above. > > I guess that should be kept, because we want 0, except if > > device_property_read_u32 provides a different value. > > Yes, this was an oversight from me, will restore n_latch = 0 at the top > of the function. Thanks for catching that.
Am Donnerstag, 20. Februar 2025, 10:56:52 MEZ schrieb Quentin Schulz: > From: Quentin Schulz <quentin.schulz@cherry.de> > > The PCA9670, PCA9671, PCA9672 and PCA9673 all have a RESETN input pin > that is used to reset the I2C GPIO expander. > > One needs to hold this pin low for at least 4us and the reset should be > finished after about 100us according to the datasheet[1]. Once the reset > is done, the "registers and I2C-bus state machine will be held in their > default state until the RESET input is once again HIGH.". > > Because the logic is reset, the latch values eventually provided in the > Device Tree via lines-initial-states property are inapplicable so they > are simply ignored if a reset GPIO is provided. > > [1] https://www.nxp.com/docs/en/data-sheet/PCA9670.pdf 8.5 and fig 22. > Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de> With the gpio-consumer fixed, reset-gpio handling works nicely on my rk3588-tiger-haikou with the DSI display overlay, so Tested-by: Heiko Stuebner <heiko@sntech.de>
diff --git a/drivers/gpio/gpio-pcf857x.c b/drivers/gpio/gpio-pcf857x.c index 7c57eaeb0afeba8953d998d8eec60a65b40efb6d..94077208e24ae99a1e8762e783f0eabc580fa520 100644 --- a/drivers/gpio/gpio-pcf857x.c +++ b/drivers/gpio/gpio-pcf857x.c @@ -5,6 +5,7 @@ * Copyright (C) 2007 David Brownell */ +#include <linux/delay.h> #include <linux/gpio/driver.h> #include <linux/i2c.h> #include <linux/interrupt.h> @@ -272,12 +273,11 @@ static const struct irq_chip pcf857x_irq_chip = { static int pcf857x_probe(struct i2c_client *client) { + struct gpio_desc *rstn_gpio; struct pcf857x *gpio; - unsigned int n_latch = 0; + unsigned int n_latch; int status; - device_property_read_u32(&client->dev, "lines-initial-states", &n_latch); - /* Allocate, initialize, and register this gpio_chip. */ gpio = devm_kzalloc(&client->dev, sizeof(*gpio), GFP_KERNEL); if (!gpio) @@ -297,6 +297,29 @@ static int pcf857x_probe(struct i2c_client *client) gpio->chip.direction_output = pcf857x_output; gpio->chip.ngpio = (uintptr_t)i2c_get_match_data(client); + rstn_gpio = devm_gpiod_get_optional(&client->dev, "reset", GPIOD_OUT_HIGH); + if (IS_ERR(rstn_gpio)) { + return dev_err_probe(&client->dev, PTR_ERR(rstn_gpio), + "failed to get reset GPIO\n"); + } + + if (rstn_gpio) { + /* Reset already held with devm_gpiod_get_optional with GPIOD_OUT_HIGH */ + usleep_range(4, 8); /* tw(rst) > 4us */ + gpiod_set_value(rstn_gpio, 0); + usleep_range(100, 200); /* trst > 100uS */ + + /* + * Reset "will initialize to their default states of all I/Os to + * inputs with weak current source to VDD", which is the same as + * writing 1 for all I/Os which is 0 in n_latch. + */ + n_latch = 0; + } else { + device_property_read_u32(&client->dev, "lines-initial-states", + &n_latch); + } + /* NOTE: the OnSemi jlc1562b is also largely compatible with * these parts, notably for output. It has a low-resolution * DAC instead of pin change IRQs; and its inputs can be the