Re: [PATCH v2 2/6] gpio: brcmstb: Add interrupt support

[Gregory Fong <gregory.0xf0@xxxxxxxxx>]

On Fri, May 29, 2015 at 5:10 PM, Brian Norris
<computersforpeace@xxxxxxxxx> wrote:
> A few small comments:
>
> On Thu, May 28, 2015 at 07:14:06PM -0700, Gregory Fong wrote:
>> v2:
>> - since imask member of bank struct was removed, just read and write from mask
>>   reg and don't maintain a shadow
>
> ^^ this comment may be addressing what I'm going to ask about below? Not
> sure why this was changed, actually.

Yes, see below...

>
>> - warn on invalid IRQs
>> - move some irq setup to a separate function since probe is getting unwieldy
>>
>>  drivers/gpio/Kconfig        |   1 +
>>  drivers/gpio/gpio-brcmstb.c | 276 ++++++++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 277 insertions(+)
>>
> ...
>> diff --git a/drivers/gpio/gpio-brcmstb.c b/drivers/gpio/gpio-brcmstb.c
>> index 7a3cb1f..b9962ff 100644
>> --- a/drivers/gpio/gpio-brcmstb.c
>> +++ b/drivers/gpio/gpio-brcmstb.c
> ...
>> @@ -63,6 +69,231 @@ brcmstb_gpio_gc_to_priv(struct gpio_chip *gc)
> ...
>> +static void brcmstb_gpio_irq_bank_handler(int irq,
>> +             struct brcmstb_gpio_bank *bank)
>> +{
>> +     struct brcmstb_gpio_priv *priv = bank->parent_priv;
>> +     void __iomem *reg_base = priv->reg_base;
>> +     unsigned long status;
>> +     unsigned long flags;
>> +
>> +     spin_lock_irqsave(&bank->bgc.lock, flags);
>> +     while ((status = bank->bgc.read_reg(reg_base + GIO_STAT(bank->id)) &
>> +                      bank->bgc.read_reg(reg_base + GIO_MASK(bank->id)))) {
>
> In case you do run this loop multiple times (multiple interrupts in
> progress?), wouldn't it make sense to stash the mask exactly once,
> outside the loop? It's probably not a real big deal in practice, I
> guess.

I made this change after Linus's remark at
https://lkml.org/lkml/2015/5/12/303 on v1, which I agree with mostly
since it's a premature optimization---I haven't determined whether
keeping a shadow mask actually helps performance at all in practice,
and better to keep it simpler without actual data.

>
>> +             int bit;
>> +             for_each_set_bit(bit, &status, 32) {
>> +                     int hwirq = bank->bgc.gc.base -
>> +                             priv->gpio_base + bit;
>> +                     int child_irq =
>> +                             irq_find_mapping(priv->irq_domain,
>> +                                              hwirq);
>> +                     u32 stat = bank->bgc.read_reg(reg_base +
>> +                                                   GIO_STAT(bank->id));
>> +                     if (bit >= bank->width)
>> +                             dev_warn(&priv->pdev->dev,
>> +                                      "IRQ for invalid GPIO (bank=%d, offset=%d)\n",
>> +                                      bank->id, bit);
>> +                     bank->bgc.write_reg(reg_base + GIO_STAT(bank->id),
>> +                                         stat | BIT(bit));
>> +                     generic_handle_irq(child_irq);
>> +             }
>> +     }
>> +     spin_unlock_irqrestore(&bank->bgc.lock, flags);
>> +}
> ...
>> @@ -153,6 +410,16 @@ static int brcmstb_gpio_probe(struct platform_device *pdev)
>>       priv->reg_base = reg_base;
>>       priv->pdev = pdev;
>>
>> +     if (of_find_property(np, "interrupt-controller", NULL)) {
>
> of_property_read_bool()?

OK.

>
>> +             priv->parent_irq = platform_get_irq(pdev, 0);
>> +             if (priv->parent_irq < 0) {
>> +                     dev_err(dev, "Couldn't get IRQ");
>> +                     return -ENOENT;
>> +             }
>> +     } else {
>> +             priv->parent_irq = -ENOENT;
>> +     }
>> +
>>       INIT_LIST_HEAD(&priv->bank_list);
>>       if (brcmstb_gpio_sanity_check_banks(dev, np, res))
>>               return -EINVAL;
>
> Otherwise, looks OK to my inexpert eyes.
>
> Reviewed-by: Brian Norris <computersforpeace@xxxxxxxxx>
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