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

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Date:   Sat, 2 May 2020 15:03:54 -0400
From:   William Breathitt Gray <vilhelm.gray@...il.com>
To:     Syed Nayyar Waris <syednwaris@...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 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.

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
> 

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