On Thu, Sep 21, 2017 at 3:04 AM, Florian Fainelli <f.fainelli@xxxxxxxxx> wrote: > It may happen that a device needs to force applying a state, e.g: > because it only defines one state of pin states (default) but loses > power/register contents when entering low power modes. Add a > pinctrl_dev::flags bitmask to help describe future quirks and define > PINCTRL_FLG_FORCE_STATE as such a settable flag. > > Signed-off-by: Florian Fainelli <f.fainelli@xxxxxxxxx> But I'm uncertain about the design. A while back, I applied this patch to the GPIO subsystem: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/include/linux/gpio/machine.h?id=05f479bf7d239f01ff6546f2bdeb14ad0fe65601 commit 05f479bf7d239f01ff6546f2bdeb14ad0fe65601 Author: Charles Keepax <ckeepax@xxxxxxxxxxxxxxxxxxxxxxxxxxx> Date: Tue May 23 15:47:29 2017 +0100 gpio: Add new flags to control sleep status of GPIOs Add new flags to allow users to specify that they are not concerned with the status of GPIOs whilst in a sleep/low power state. Signed-off-by: Charles Keepax <ckeepax@xxxxxxxxxxxxxxxxxxxxxxxxxxx> Acked-by: Rob Herring <robh@xxxxxxxxxx> Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx> diff --git a/include/linux/gpio/machine.h b/include/linux/gpio/machine.h index c0d712d22b07..13adadf53c09 100644 --- a/include/linux/gpio/machine.h +++ b/include/linux/gpio/machine.h @@ -9,6 +9,8 @@ enum gpio_lookup_flags { GPIO_ACTIVE_LOW = (1 << 0), GPIO_OPEN_DRAIN = (1 << 1), GPIO_OPEN_SOURCE = (1 << 2), + GPIO_SLEEP_MAINTAIN_VALUE = (0 << 3), + GPIO_SLEEP_MAY_LOOSE_VALUE = (1 << 3), }; Charles is also working on pin control and will probably have some input on design. Maybe we could do the same: a flag to maintain the value and a flag to allow it to be lost across suspend/resume, which is the core issue here. Your case is analogous to GPIO_SLEEP_MAY_LOOSE_VALUE and you restore the state when you come back from sleep. Note how gpiolib does this: bool gpiochip_line_is_persistent(struct gpio_chip *chip, unsigned int offset) { if (offset >= chip->ngpio) return false; return !test_bit(FLAG_SLEEP_MAY_LOOSE_VALUE, &chip->gpiodev->descs[offset].flags); } EXPORT_SYMBOL_GPL(gpiochip_line_is_persistent); (Notice ! in front of test_bit(), the name of the function makes sense.) Then the driver in drivers/gpio/gpio-arizona.c does some special quirks like this: static int arizona_gpio_direction_in(struct gpio_chip *chip, unsigned offset) { struct arizona_gpio *arizona_gpio = gpiochip_get_data(chip); struct arizona *arizona = arizona_gpio->arizona; bool persistent = gpiochip_line_is_persistent(chip, offset); bool change; int ret; ret = regmap_update_bits_check(arizona->regmap, ARIZONA_GPIO1_CTRL + offset, ARIZONA_GPN_DIR, ARIZONA_GPN_DIR, &change); if (ret < 0) return ret; if (change && persistent) { pm_runtime_mark_last_busy(chip->parent); pm_runtime_put_autosuspend(chip->parent); } return 0; } So what this driver does is allow the GPIO block to loose power using runtime PM if and only if the line is flagged as persistent, i.e. it will not loose its state when sleeping, so let it sleep. Next point, this commit from Baolin: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt?id=6606bc9dee63ad8cda2cc310d2ad5992673a785a output-low - set the pin to output mode with low level output-high - set the pin to output mode with high level +sleep-hardware-state - indicate this is sleep related state which will be programmed + into the registers for the sleep state. slew-rate - set the slew rate This is another thing: here we are defining a state that will be managed by autonomous hardware. The state settings will be poked into some special registers that will automatically take effect when the system goes into sleep. This is a hardware-induced state: the SLEEP line for the entire SoC is asserted. What you want is something different: a flag like: sleep-restore-state - indicate that this state needs to be restored after sleep as the hardware loose states when sleeping. The driver could look for this in a more granular per-state manner, instead of all states of the pin controller being restored, we mark what states need to be restored on the way up after sleep. What are your thoughts about this? I do not rule out a global flag for the whole controller, it is just a bit confusing if we start to have per-state, per-pin and per-controller sleep behaviour. If we have to have this we have to, but I want to fully understand the problem first. Yours, Linus Walleij -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
