On Wednesday 14 January 2015 11:43:54 Alexandre Courbot wrote:
> On Tue, Jan 13, 2015 at 7:37 PM, Rojhalat Ibrahim <[email protected]> wrote:
> > Add set_multiple functions to the generic driver for memory-mapped GPIO
> > controllers to improve performance when setting multiple outputs
> > simultaneously.
>
> Great idea ; this driver is an obvious candidate to support this.
>
> >
> > Signed-off-by: Rojhalat Ibrahim <[email protected]>
> > ---
> > drivers/gpio/gpio-generic.c | 79
> > ++++++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 79 insertions(+)
> >
> > diff --git a/drivers/gpio/gpio-generic.c b/drivers/gpio/gpio-generic.c
> > index 16f6115..cb6d0b7 100644
> > --- a/drivers/gpio/gpio-generic.c
> > +++ b/drivers/gpio/gpio-generic.c
> > @@ -160,6 +160,31 @@ static void bgpio_set(struct gpio_chip *gc, unsigned
> > int gpio, int val)
> > spin_unlock_irqrestore(&bgc->lock, flags);
> > }
> >
> > +static void bgpio_set_multiple(struct gpio_chip *gc, unsigned long *mask,
> > + unsigned long *bits)
> > +{
> > + struct bgpio_chip *bgc = to_bgpio_chip(gc);
> > + unsigned long flags;
> > + int i;
> > +
> > + spin_lock_irqsave(&bgc->lock, flags);
> > +
> > + for (i = 0; i < bgc->bits; i++) {
> > + if (*mask == 0)
> > + break;
> > + if (__test_and_clear_bit(i, mask)) {
> > + if (test_bit(i, bits))
> > + bgc->data |= bgc->pin2mask(bgc, i);
> > + else
> > + bgc->data &= ~bgc->pin2mask(bgc, i);
> > + }
> > + }
> > +
> > + bgc->write_reg(bgc->reg_dat, bgc->data);
> > +
> > + spin_unlock_irqrestore(&bgc->lock, flags);
> > +}
> > +
> > static void bgpio_set_with_clear(struct gpio_chip *gc, unsigned int gpio,
> > int val)
> > {
> > @@ -172,6 +197,32 @@ static void bgpio_set_with_clear(struct gpio_chip *gc,
> > unsigned int gpio,
> > bgc->write_reg(bgc->reg_clr, mask);
> > }
> >
> > +static void bgpio_set_multiple_with_clear(struct gpio_chip *gc,
> > + unsigned long *mask,
> > + unsigned long *bits)
> > +{
> > + struct bgpio_chip *bgc = to_bgpio_chip(gc);
> > + unsigned long set_mask = 0;
> > + unsigned long clear_mask = 0;
> > + int i;
> > +
> > + for (i = 0; i < bgc->bits; i++) {
> > + if (*mask == 0)
> > + break;
> > + if (__test_and_clear_bit(i, mask)) {
> > + if (test_bit(i, bits))
> > + set_mask |= bgc->pin2mask(bgc, i);
> > + else
> > + clear_mask |= bgc->pin2mask(bgc, i);
> > + }
> > + }
> > +
> > + if (set_mask)
> > + bgc->write_reg(bgc->reg_set, set_mask);
> > + if (clear_mask)
> > + bgc->write_reg(bgc->reg_clr, clear_mask);
> > +}
>
> Isn't this function missing spinlock protection?
>
I followed the lead of the bgpio_set_with_clear function which also does not
use a spinlock. With dedicated set and clear registers it shouldn't be
necessary.
> > +
> > static void bgpio_set_set(struct gpio_chip *gc, unsigned int gpio, int val)
> > {
> > struct bgpio_chip *bgc = to_bgpio_chip(gc);
> > @@ -190,6 +241,31 @@ static void bgpio_set_set(struct gpio_chip *gc,
> > unsigned int gpio, int val)
> > spin_unlock_irqrestore(&bgc->lock, flags);
> > }
> >
> > +static void bgpio_set_multiple_set(struct gpio_chip *gc, unsigned long
> > *mask,
> > + unsigned long *bits)
> > +{
> > + struct bgpio_chip *bgc = to_bgpio_chip(gc);
> > + unsigned long flags;
> > + int i;
> > +
> > + spin_lock_irqsave(&bgc->lock, flags);
> > +
> > + for (i = 0; i < bgc->bits; i++) {
> > + if (*mask == 0)
> > + break;
> > + if (__test_and_clear_bit(i, mask)) {
> > + if (test_bit(i, bits))
> > + bgc->data |= bgc->pin2mask(bgc, i);
> > + else
> > + bgc->data &= ~bgc->pin2mask(bgc, i);
> > + }
> > + }
> > +
> > + bgc->write_reg(bgc->reg_set, bgc->data);
> > +
> > + spin_unlock_irqrestore(&bgc->lock, flags);
> > +}
>
> Couldn't it be possible to factorize a great deal of these 3 functions?
>
> The only difference between bgpio_set_multiple() and
> bgpio_set_multiple_set() is the register that is written. In
> bgpio_set_multiple_set(), you only handle the set and cleared bits in
> different variables.
>
> How about a private function that looks like this:
>
> static void __bgpio_multiple_get_masks(struct bgpio_chip *bgc,
> unsigned long *mask, unsigned long
> *bits,
> unsigned long *set_mask,
> unsigned long *clear_mask)
> {
> int i;
>
> *set_mask = 0;
> *clear_mask = 0;
>
> for (i = 0; i < bgc->bits; i++) {
> if (*mask == 0)
> break;
> if (__test_and_clear_bit(i, mask)) {
> if (test_bit(i, bits))
> *set_mask |= bgc->pin2mask(bgc, i);
> else
> *clear_mask |= bgc->pin2mask(bgc, i);
> }
> }
> }
>
> Then, you could have:
>
> static void bgpio_set_multiple_with_clear(struct gpio_chip *gc,
> unsigned long *mask,
> unsigned long *bits)
> {
> struct bgpio_chip *bgc = to_bgpio_chip(gc);
> unsigned long flags;
> unsigned long set_mask, clear_mask;
>
> spin_lock_irqsave(&bgc->lock, flags);
>
> __bgpio_multiple_get_masks(bgc, mask, bits, &set_mask, &clear_mask);
>
> if (set_mask)
> bgc->write_reg(bgc->reg_set, set_mask);
> if (clear_mask)
> bgc->write_reg(bgc->reg_clr, clear_mask);
>
> spin_unlock_irqrestore(&bgc->lock, flags);
> }
>
> and:
>
> static void bgpio_set_multiple(struct gpio_chip *gc, unsigned long *mask,
> unsigned long *bits)
> {
> struct bgpio_chip *bgc = to_bgpio_chip(gc);
> unsigned long flags;
> unsigned long set_mask, clear_mask;
>
> spin_lock_irqsave(&bgc->lock, flags);
>
> __bgpio_multiple_get_masks(bgc, mask, bits, &set_mask, &clear_mask);
>
> bgc->data |= set_mask;
> bgc->data &= ~clear_mask;
>
> bgc->write_reg(bgc->reg_dat, bgc->data);
>
> spin_unlock_irqrestore(&bgc->lock, flags);
> }
>
> ... and something similar for __bgpio_multiple_get_masks. This would
> probably result in a smaller patch on top or reducing duplicate code.
You are right, of course. I'll post a revised version.
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