On 27/10/2023 13:27, Krzysztof Kozlowski wrote: > On 27/10/2023 05:31, Chris Packham wrote: >> 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 Cc: Mark, Also this part is not true. If the bus is non-discoverable, then it is possible to have reset-gpios in each probed device. You can share GPIOs, so no problem with -EBUSY at all. The problem is doing reset: 1. in proper moment for all devices 2. without affecting other devices when one unbinds/remove() The (2) above is not solveable easy in kernel and we already had nice talks about it just few days ago: 1. Apple case: https://social.treehouse.systems/@marcan/111268780311634160 2. my WSA884x: https://lore.kernel.org/alsa-devel/84f9f1c4-0627-4986-8160-b4ab99469b81@xxxxxxxxxx/ Last, I would like to apologize to you Chris. I understand that bringing such feedback at v5 is not that good. I had plenty of time to say something earlier, so this is not really professional from my side. I am sorry, just my brain did not connect all these topics together. I apologize. Best regards, Krzysztof >> 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@xxxxxxxxxxxxxxxxxxx> >> --- >> >> 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; > > No, this should be solved by core - for entire I2C at minimum. This is > not specific to this device.
