linux-kernel - Re: [PATCH v4 4/4] gpio: xilinx: Utilize for_each_set

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Date:   Sun, 3 May 2020 04:55:12 +0530
From:   Syed Nayyar Waris <syednwaris@...il.com>
To:     William Breathitt Gray <vilhelm.gray@...il.com>
Cc:     akpm@...ux-foundation.org, andriy.shevchenko@...ux.intel.com,
        linus.walleij@...aro.org, bgolaszewski@...libre.com,
        michal.simek@...inx.com, linux-gpio@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 4/4] gpio: xilinx: Utilize for_each_set_clump macro

On Sat, May 02, 2020 at 03:03:54PM -0400, William Breathitt Gray wrote:
> On Sun, May 03, 2020 at 12:21:54AM +0530, Syed Nayyar Waris wrote:
> > This patch reimplements the xgpio_set_multiple function in
> > drivers/gpio/gpio-xilinx.c to use the new for_each_set_clump macro.
> > Instead of looping for each bit in xgpio_set_multiple
> > function, now we can check each channel at a time and save cycles.
> > 
> > Cc: Linus Walleij <linus.walleij@...aro.org>
> > Cc: Bartosz Golaszewski <bgolaszewski@...libre.com>
> > Cc: Michal Simek <michal.simek@...inx.com>
> > Signed-off-by: Syed Nayyar Waris <syednwaris@...il.com>
> > Signed-off-by: William Breathitt Gray <vilhelm.gray@...il.com>
> > ---
> > Changes in v4:
> >  - Minor change: Hardcode value for better code readability.
> > 
> > Changes in v3:
> >  - No change.
> > 
> > Changes in v2:
> >  - No change.
> > 
> >  drivers/gpio/gpio-xilinx.c | 64 ++++++++++++++++++++------------------
> >  1 file changed, 34 insertions(+), 30 deletions(-)
> > 
> > diff --git a/drivers/gpio/gpio-xilinx.c b/drivers/gpio/gpio-xilinx.c
> > index 67f9f82e0db0..67c5eeaf1bb9 100644
> > --- a/drivers/gpio/gpio-xilinx.c
> > +++ b/drivers/gpio/gpio-xilinx.c
> > @@ -136,39 +136,43 @@ static void xgpio_set(struct gpio_chip *gc, unsigned int gpio, int val)
> >  static void xgpio_set_multiple(struct gpio_chip *gc, unsigned long *mask,
> >  			       unsigned long *bits)
> >  {
> > -	unsigned long flags;
> > +	unsigned long flags[2];
> >  	struct xgpio_instance *chip = gpiochip_get_data(gc);
> > -	int index = xgpio_index(chip, 0);
> > -	int offset, i;
> > -
> > -	spin_lock_irqsave(&chip->gpio_lock[index], flags);
> > -
> > -	/* Write to GPIO signals */
> > -	for (i = 0; i < gc->ngpio; i++) {
> > -		if (*mask == 0)
> > -			break;
> > -		/* Once finished with an index write it out to the register */
> > -		if (index !=  xgpio_index(chip, i)) {
> > -			xgpio_writereg(chip->regs + XGPIO_DATA_OFFSET +
> > -				       index * XGPIO_CHANNEL_OFFSET,
> > -				       chip->gpio_state[index]);
> > -			spin_unlock_irqrestore(&chip->gpio_lock[index], flags);
> > -			index =  xgpio_index(chip, i);
> > -			spin_lock_irqsave(&chip->gpio_lock[index], flags);
> > -		}
> > -		if (__test_and_clear_bit(i, mask)) {
> > -			offset =  xgpio_offset(chip, i);
> > -			if (test_bit(i, bits))
> > -				chip->gpio_state[index] |= BIT(offset);
> > -			else
> > -				chip->gpio_state[index] &= ~BIT(offset);
> > -		}
> > +	u32 *const state = chip->gpio_state;
> > +	unsigned int *const width = chip->gpio_width;
> > +	const unsigned long state_size = 32;
> > +	const unsigned long total_state_bits = state_size * 2;
> 
> Hello Syed,
> 
> I don't think there's much need for these two variables either. You can
> remove the state_size and total_state_bits variables, and instead inline
> 32 and 64 directly in your code below.

Hi. Have sent v5 patchset incorporating your review comment.

Thank you.

> 
> William Breathitt Gray
> 
> > +	unsigned long offset, clump;
> > +	size_t index;
> > +
> > +	DECLARE_BITMAP(old, 64);
> > +	DECLARE_BITMAP(new, 64);
> > +	DECLARE_BITMAP(changed, 64);
> > +
> > +	spin_lock_irqsave(&chip->gpio_lock[0], flags[0]);
> > +	spin_lock_irqsave(&chip->gpio_lock[1], flags[1]);
> > +
> > +	bitmap_set_value(old, state[0], 0, width[0]);
> > +	bitmap_set_value(old, state[1], width[0], width[1]);
> > +	bitmap_replace(new, old, bits, mask, gc->ngpio);
> > +
> > +	bitmap_set_value(old, state[0], 0, state_size);
> > +	bitmap_set_value(old, state[1], state_size, state_size);
> > +	state[0] = bitmap_get_value(new, 0, width[0]);
> > +	state[1] = bitmap_get_value(new, width[0], width[1]);
> > +	bitmap_set_value(new, state[0], 0, state_size);
> > +	bitmap_set_value(new, state[1], state_size, state_size);
> > +	bitmap_xor(changed, old, new, total_state_bits);
> > +
> > +	for_each_set_clump(offset, clump, changed, total_state_bits, state_size) {
> > +		index = offset / state_size;
> > +		xgpio_writereg(chip->regs + XGPIO_DATA_OFFSET +
> > +				index * XGPIO_CHANNEL_OFFSET,
> > +				state[index]);
> >  	}
> >  
> > -	xgpio_writereg(chip->regs + XGPIO_DATA_OFFSET +
> > -		       index * XGPIO_CHANNEL_OFFSET, chip->gpio_state[index]);
> > -
> > -	spin_unlock_irqrestore(&chip->gpio_lock[index], flags);
> > +	spin_unlock_irqrestore(&chip->gpio_lock[1], flags[1]);
> > +	spin_unlock_irqrestore(&chip->gpio_lock[0], flags[0]);
> >  }
> >  
> >  /**
> > -- 
> > 2.26.2
> >