[PATCH v5 2/2] i2c: mv64xxx: add an optional bus-reset-gpios property

Chris Packham
2023-10-27T03:31:19Z

Some hardware designs have a GPIO used to control the reset of all the
devices on and I2C bus. It's not possible for every child node to
declare a reset-gpios property as only the first device probed would be
able to successfully request it (the others will get -EBUSY). Represent
this kind of hardware design by associating the bus-reset-gpios with the
parent I2C bus. The reset line will be released prior to the child I2C
devices being probed.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
---

Notes:
Changes in v5:
- Rename reset-gpios and reset-duration-us to bus-reset-gpios and
bus-reset-duration-us as requested by Wolfram
Changes in v4:
- Add missing gpio/consumer.h
- use fsleep() for enforcing reset-duration
Changes in v3:
- Rename reset-delay to reset-duration
- Use reset-duration-us property to control the reset pulse rather than
delaying after the reset
Changes in v2:
- Add a property to cover the length of delay after releasing the reset
GPIO
- Use dev_err_probe() when requesing the GPIO fails

drivers/i2c/busses/i2c-mv64xxx.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

diff --git a/drivers/i2c/busses/i2c-mv64xxx.c b/drivers/i2c/busses/i2c-mv64xxx.c
index efd28bbecf61..6e2762d22e5a 100644
--- a/drivers/i2c/busses/i2c-mv64xxx.c
+++ b/drivers/i2c/busses/i2c-mv64xxx.c
@@ -13,6 +13,7 @@
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/spinlock.h>
+#include <linux/gpio/consumer.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
#include <linux/mv643xx_i2c.h>
@@ -160,6 +161,7 @@ struct mv64xxx_i2c_data {
bool clk_n_base_0;
struct i2c_bus_recovery_info rinfo;
bool atomic;
+ struct gpio_desc *reset_gpio;
};

static struct mv64xxx_i2c_regs mv64xxx_i2c_regs_mv64xxx = {
@@ -1036,6 +1038,7 @@ mv64xxx_i2c_probe(struct platform_device *pd)
struct mv64xxx_i2c_data *drv_data;
struct mv64xxx_i2c_pdata *pdata = dev_get_platdata(&pd->dev);
struct resource *res;
+ u32 reset_duration;
int rc;

if ((!pdata && !pd->dev.of_node))
@@ -1083,6 +1086,14 @@ mv64xxx_i2c_probe(struct platform_device *pd)
if (drv_data->irq < 0)
return drv_data->irq;

+ drv_data->reset_gpio = devm_gpiod_get_optional(&pd->dev, "bus-reset", GPIOD_OUT_HIGH);
+ if (IS_ERR(drv_data->reset_gpio))
+ return dev_err_probe(&pd->dev, PTR_ERR(drv_data->reset_gpio),
+ "Cannot get reset gpio\n");
+ rc = device_property_read_u32(&pd->dev, "bus-reset-duration-us", &reset_duration);
+ if (rc)
+ reset_duration = 1;
+
if (pdata) {
drv_data->freq_m = pdata->freq_m;
drv_data->freq_n = pdata->freq_n;
@@ -1121,6 +1132,11 @@ mv64xxx_i2c_probe(struct platform_device *pd)
goto exit_disable_pm;
}

+ if (drv_data->reset_gpio) {
+ fsleep(reset_duration);
+ gpiod_set_value_cansleep(drv_data->reset_gpio, 0);
+ }
+
rc = request_irq(drv_data->irq, mv64xxx_i2c_intr, 0,
MV64XXX_I2C_CTLR_NAME, drv_data);
if (rc) {
--
2.42.0