Messages in this thread Patch in this message | | | Date | Mon, 11 Jul 2022 18:08:53 +0400 | From | Yassine Oudjana <> | Subject | Re: [PATCH 3/3] media: i2c: ak7375: Add regulator management |
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On Mon, Jul 11 2022 at 15:34:23 +0200, Jacopo Mondi <jacopo@jmondi.org> wrote: > Hello Yassine > > On Mon, Jul 11, 2022 at 08:28:39AM +0400, Yassine Oudjana wrote: >> From: Yassine Oudjana <y.oudjana@protonmail.com> >> >> Make the driver get needed regulators on probe and enable/disable >> them on runtime PM callbacks. >> >> Signed-off-by: Yassine Oudjana <y.oudjana@protonmail.com> >> --- >> drivers/media/i2c/ak7375.c | 39 >> ++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 39 insertions(+) >> >> diff --git a/drivers/media/i2c/ak7375.c b/drivers/media/i2c/ak7375.c >> index 40b1a4aa846c..59d5cb00e3ba 100644 >> --- a/drivers/media/i2c/ak7375.c >> +++ b/drivers/media/i2c/ak7375.c >> @@ -6,6 +6,7 @@ >> #include <linux/i2c.h> >> #include <linux/module.h> >> #include <linux/pm_runtime.h> >> +#include <linux/regulator/consumer.h> >> #include <media/v4l2-ctrls.h> >> #include <media/v4l2-device.h> >> >> @@ -23,17 +24,32 @@ >> */ >> #define AK7375_CTRL_STEPS 64 >> #define AK7375_CTRL_DELAY_US 1000 >> +/* >> + * The vcm takes around 3 ms to power on and start taking >> + * I2C messages. This value was found experimentally due to >> + * lack of documentation. 2 ms is added as a safety margin. >> + */ >> +#define AK7375_POWER_DELAY_US 5000 >> >> #define AK7375_REG_POSITION 0x0 >> #define AK7375_REG_CONT 0x2 >> #define AK7375_MODE_ACTIVE 0x0 >> #define AK7375_MODE_STANDBY 0x40 >> >> +static const char * const ak7375_supply_names[] = { >> + "vdd", >> + "vio", >> +}; >> + >> +#define AK7375_NUM_SUPPLIES ARRAY_SIZE(ak7375_supply_names) >> + >> /* ak7375 device structure */ >> struct ak7375_device { >> struct v4l2_ctrl_handler ctrls_vcm; >> struct v4l2_subdev sd; >> struct v4l2_ctrl *focus; >> + struct regulator_bulk_data supplies[AK7375_NUM_SUPPLIES]; >> + >> /* active or standby mode */ >> bool active; >> }; >> @@ -132,6 +148,7 @@ static int ak7375_init_controls(struct >> ak7375_device *dev_vcm) >> static int ak7375_probe(struct i2c_client *client) >> { >> struct ak7375_device *ak7375_dev; >> + int i; > > I would have moved this one down to maintain variable declaration > in the in-famous reverse-xmas-tree ordering. Up to you.
I'm used to declaring variables in the order of first use, but I don't really mind it either way. I'll move it down.
> >> int ret; >> >> ak7375_dev = devm_kzalloc(&client->dev, sizeof(*ak7375_dev), >> @@ -139,6 +156,17 @@ static int ak7375_probe(struct i2c_client >> *client) >> if (!ak7375_dev) >> return -ENOMEM; >> >> + for (i = 0; i < AK7375_NUM_SUPPLIES; i++) >> + ak7375_dev->supplies[i].supply = ak7375_supply_names[i]; >> + >> + ret = devm_regulator_bulk_get(&client->dev, AK7375_NUM_SUPPLIES, >> + ak7375_dev->supplies); >> + if (ret) { >> + dev_err(&client->dev, "Failed to get regulators: %pe", >> + ERR_PTR(ret)); >> + return ret; >> + } >> + >> v4l2_i2c_subdev_init(&ak7375_dev->sd, client, &ak7375_ops); >> ak7375_dev->sd.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE; >> ak7375_dev->sd.internal_ops = &ak7375_int_ops; >> @@ -210,6 +238,10 @@ static int __maybe_unused >> ak7375_vcm_suspend(struct device *dev) >> if (ret) >> dev_err(dev, "%s I2C failure: %d\n", __func__, ret); >> >> + ret = regulator_bulk_disable(AK7375_NUM_SUPPLIES, >> ak7375_dev->supplies); >> + if (ret) >> + return ret; >> + >> ak7375_dev->active = false; >> >> return 0; >> @@ -230,6 +262,13 @@ static int __maybe_unused >> ak7375_vcm_resume(struct device *dev) >> if (ak7375_dev->active) >> return 0; >> >> + ret = regulator_bulk_enable(AK7375_NUM_SUPPLIES, >> ak7375_dev->supplies); >> + if (ret) >> + return ret; >> + >> + /* Wait for vcm to become ready */ >> + usleep_range(AK7375_POWER_DELAY_US, AK7375_POWER_DELAY_US + 10); >> + > > Isn't 10usec a very small delay to be given to usleep_range() for a > delay of at least 3msec ? Also assuming 5msec just to be safe seems a > little arbitrary. Adding 2 milliseconds in the wakeup path introduces > a non-negligible delay.
I must admit that I didn't give it too much thought. I just did it similar to the other delay used in this driver (AK7375_CTRL_DELAY_US). As for adding 2ms, I don't know what the worst case wake-up time is since I don't have a datasheet on hand, so I just wanted to stay safe. Also, this driver doesn't really recover if it fails to resume (which is what used to happen before adding a delay). Rounding up to 5ms felt good enough.
> > It's likely a detail, but according to > Documentation/timers/timers-howto.rst > > Since usleep_range is built on top of hrtimers, the > wakeup will be very precise (ish), thus a simple > usleep function would likely introduce a large number > of undesired interrupts. > > With the introduction of a range, the scheduler is > free to coalesce your wakeup with any other wakeup > that may have happened for other reasons, or at the > worst case, fire an interrupt for your upper bound. > > The larger a range you supply, the greater a chance > that you will not trigger an interrupt; this should > be balanced with what is an acceptable upper bound on > delay / performance for your specific code path. Exact > tolerances here are very situation specific, thus it > is left to the caller to determine a reasonable range. > > If you have a min of 3msec I would try with a range of (3000, 3500). > What do you think ?
Seems good. I haven't yet had it fail to power on within 3ms of turning on regulators so I guess there is no reason to worry about it.
>> >> ret = ak7375_i2c_write(ak7375_dev, AK7375_REG_CONT, >> AK7375_MODE_ACTIVE, 1); >> if (ret) { >> -- >> 2.37.0 >
Thanks for the review, Yassine
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