On Fri, Mar 6, 2015 at 7:51 PM, Andrew Bresticker <abrestic@xxxxxxxxxxxx> wrote:
> On Fri, Mar 6, 2015 at 3:55 AM, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
>>> +static inline void gpio_writel(struct pistachio_gpio_bank *bank, u32 val,
>>> + u32 reg)
>>> +{
>>> + writel(val, bank->base + reg);
>>> +}
>>
>> I don't see the point of these special readl/writel accessors. Just
>> use readl/writel
>> directly. Or consider readl/writel_relaxed() if MIPS has this.
>
> I actually find these useful for tracing MMIO accesses within a driver
> and it seems many other drivers do this too. I can drop them though
> if you'd prefer.
OK does it turn up in ftrace etc? I was thinking these would be
inlined by the compiler (especially since you even state they shall
be inlined) and the symbols trashed?
>> (...)
>>> +static int pistachio_gpio_register(struct pistachio_pinctrl *pctl)
>>> +{
>>> + struct device_node *child, *node = pctl->dev->of_node;
>>> + struct pistachio_gpio_bank *bank;
>>> + unsigned int i = 0;
>>> + int irq, ret = 0;
>>> +
>>> + for_each_child_of_node(node, child) {
>>> + if (!of_find_property(child, "gpio-controller", NULL))
>>> + continue;
>>
>> So why not instead specify "simple-bus" as compatible on the parent node
>> and have each subnode be its own device (simple-bus will spawn platform
>> devices for all subnodes).
>>
>> Overall this composite-device pattern is discouraged if we can instead have
>> unique devices for each bank.
>
> I think there's an issue here though if some other device probes
> between the pinctrl driver and the gpiochip drivers. Since all these
> pins are configured as GPIOs at POR, the pinctrl driver needs to clear
> the GPIO enable bit on a pin when enabling a pinmux function for that
> pin (see pistachio_pinmux_enable()). If the gpiochip driver has yet
> to probe, attempting to map the pinctrl pin to a GPIO range/pin (via
> pinctrl_find_gpio_range_from_pin()) will fail and we won't be able to
> disable the GPIO function for that pin.
I was thinking the GPIO driver part should get a -EPROBE_DEFER when
trying to call gpiochip_add_pin_range() and continue later when the
pin controller is available?
And all drivers using GPIOs in turn get a -EPROBE_DEFER when
trying to get GPIOs on a not-yet registered GPIO chip.
Sorry if I don't really know how things work now... :(
It seems like a logical way to me.
> Also it doesn't look like
> there's a good way to tell gpiolib to disable a GPIO form the pinctrl
> driver.
Define exactly what you mean by "disable". There is
pinctrl_free_gpio().
> Any ideas? I suppose I could keep the pin-to-GPIO mapping in
> the pinctrl driver in addition to expressing it in the DT with
> gpio-ranges, but that doesn't seem too nice.
The ranges shall definately be registered from the GPIO side of
the driver, that much I can tell you for sure...
Yours,
Linus Walleij
