| Message ID | 20230921133202.5828-4-wsa+renesas@sang-engineering.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Geert Uytterhoeven |
| Headers | show |
| Series | gnss: ubx: updates to support the Renesas KingFisher board | expand |
On Thu, Sep 21, 2023 at 03:32:01PM +0200, Wolfram Sang wrote: > Tested with a Renesas KingFisher board. Because my GNSS device is hooked > up via UART and I2C simultaneously, I could verify functionality by > opening/closing the GNSS device using UART and see if the corresponding > I2C device was visible on the bus. Again, please try to make the commit message self-contained (e.g. without implicitly referring to Subject). Also say something about which u-blox module this is needed for since the modules I've seen do not have a reset line. > static int ubx_set_active(struct gnss_serial *gserial) > @@ -29,6 +31,8 @@ static int ubx_set_active(struct gnss_serial *gserial) > if (ret) > return ret; > > + gpiod_set_value_cansleep(data->reset_gpio, 0); > + > return 0; > } > > @@ -37,6 +41,8 @@ static int ubx_set_standby(struct gnss_serial *gserial) > struct ubx_data *data = gnss_serial_get_drvdata(gserial); > int ret; > > + gpiod_set_value_cansleep(data->reset_gpio, 1); > + > ret = regulator_disable(data->vcc); > if (ret) > return ret; > @@ -90,6 +96,13 @@ static int ubx_probe(struct serdev_device *serdev) > if (ret < 0 && ret != -ENODEV) > goto err_free_gserial; > > + /* Start with reset asserted */ > + data->reset_gpio = devm_gpiod_get_optional(&serdev->dev, "reset", GPIOD_OUT_HIGH); > + if (IS_ERR(data->reset_gpio)) { > + ret = PTR_ERR(data->reset_gpio); > + goto err_free_gserial; > + } So this means that the reset line will be asserted indefinitely in case the GNSS receiver is not used. Are you sure that's a good idea? I don't know yet which module this is for, or how this signal is supposed to be used, but the above makes this look more like an active-high (regulator) enable signal. Perhaps that's what it is or should be modelled as (i.e. as a fixed regulator). > + > ret = gnss_serial_register(gserial); > if (ret) > goto err_free_gserial; Johan
> So this means that the reset line will be asserted indefinitely in case > the GNSS receiver is not used. Are you sure that's a good idea? Yup. Saves power. We do this for our ethernet PHYs as well. Any reasons not to do this? > I don't know yet which module this is for, or how this signal is > supposed to be used, but the above makes this look more like an > active-high (regulator) enable signal. Perhaps that's what it is or > should be modelled as (i.e. as a fixed regulator). Nope, it is a RESET_N pin.
On Mon, Oct 23, 2023 at 09:09:03AM +0200, Wolfram Sang wrote: > > So this means that the reset line will be asserted indefinitely in case > > the GNSS receiver is not used. Are you sure that's a good idea? > > Yup. Saves power. We do this for our ethernet PHYs as well. Any reasons > not to do this? AFAIK you should generally not try to use reset this way as you may end up leaking current (and possibly other complications). > > I don't know yet which module this is for, or how this signal is > > supposed to be used, but the above makes this look more like an > > active-high (regulator) enable signal. Perhaps that's what it is or > > should be modelled as (i.e. as a fixed regulator). > > Nope, it is a RESET_N pin. And the neo-m8 hardware integration manual explicitly says that it shall not be used as a disable signal: 1.5 I/O pins RESET_N: Reset input Driving RESET_N low activates a hardware reset of the system. Use this pin only to reset the module. Do not use RESET_N to turn the module on and off, since the reset state increases power consumption. Some of the other modules in this family says so explicitly also in the datasheet. Johan
diff --git a/drivers/gnss/ubx.c b/drivers/gnss/ubx.c index 9b76b101ba5e..e7d151cbc8c3 100644 --- a/drivers/gnss/ubx.c +++ b/drivers/gnss/ubx.c @@ -7,6 +7,7 @@ #include <linux/errno.h> #include <linux/gnss.h> +#include <linux/gpio/consumer.h> #include <linux/init.h> #include <linux/kernel.h> #include <linux/module.h> @@ -18,6 +19,7 @@ struct ubx_data { struct regulator *vcc; + struct gpio_desc *reset_gpio; }; static int ubx_set_active(struct gnss_serial *gserial) @@ -29,6 +31,8 @@ static int ubx_set_active(struct gnss_serial *gserial) if (ret) return ret; + gpiod_set_value_cansleep(data->reset_gpio, 0); + return 0; } @@ -37,6 +41,8 @@ static int ubx_set_standby(struct gnss_serial *gserial) struct ubx_data *data = gnss_serial_get_drvdata(gserial); int ret; + gpiod_set_value_cansleep(data->reset_gpio, 1); + ret = regulator_disable(data->vcc); if (ret) return ret; @@ -90,6 +96,13 @@ static int ubx_probe(struct serdev_device *serdev) if (ret < 0 && ret != -ENODEV) goto err_free_gserial; + /* Start with reset asserted */ + data->reset_gpio = devm_gpiod_get_optional(&serdev->dev, "reset", GPIOD_OUT_HIGH); + if (IS_ERR(data->reset_gpio)) { + ret = PTR_ERR(data->reset_gpio); + goto err_free_gserial; + } + ret = gnss_serial_register(gserial); if (ret) goto err_free_gserial;