linux-kernel - Re: [PATCH v3 2/3] pinctrl: intel: refine ->irq_set

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Date:   Thu, 15 Jun 2023 12:55:17 +0300
From:   "mika.westerberg@...ux.intel.com" <mika.westerberg@...ux.intel.com>
To:     "Jadav, Raag" <raag.jadav@...el.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "linus.walleij@...aro.org" <linus.walleij@...aro.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Sangannavar, Mallikarjunappa" 
        <mallikarjunappa.sangannavar@...el.com>,
        "N, Pandith" <pandith.n@...el.com>
Subject: Re: [PATCH v3 2/3] pinctrl: intel: refine ->irq_set_type() hook

On Thu, Jun 15, 2023 at 09:48:12AM +0000, Jadav, Raag wrote:
> > On Tue, Jun 13, 2023 at 02:20:53PM +0530, Raag Jadav wrote:
> > > Utilize a temporary variable for common shift operation in
> > > ->irq_set_type() hook and improve readability.
> > > While at it, simplify if-else-if chain and save a few bytes.
> > >
> > > add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-16 (-16)
> > > Function                                     old     new   delta
> > > intel_gpio_irq_type                          317     301     -16
> > > Total: Before=10469, After=10453, chg -0.15%
> > 
> > ...
> > 
> > >  	value = readl(reg);
> > > -
> > >  	value &= ~(PADCFG0_RXEVCFG_MASK | PADCFG0_RXINV);
> > >
> > >  	if ((type & IRQ_TYPE_EDGE_BOTH) == IRQ_TYPE_EDGE_BOTH) {
> > > -		value |= PADCFG0_RXEVCFG_EDGE_BOTH <<
> > PADCFG0_RXEVCFG_SHIFT;
> > > +		rxevcfg = PADCFG0_RXEVCFG_EDGE_BOTH;
> > >  	} else if (type & IRQ_TYPE_EDGE_FALLING) {
> > > -		value |= PADCFG0_RXEVCFG_EDGE <<
> > PADCFG0_RXEVCFG_SHIFT;
> > > -		value |= PADCFG0_RXINV;
> > > +		rxevcfg = PADCFG0_RXEVCFG_EDGE;
> > >  	} else if (type & IRQ_TYPE_EDGE_RISING) {
> > > -		value |= PADCFG0_RXEVCFG_EDGE <<
> > PADCFG0_RXEVCFG_SHIFT;
> > > +		rxevcfg = PADCFG0_RXEVCFG_EDGE;
> > >  	} else if (type & IRQ_TYPE_LEVEL_MASK) {
> > > -		if (type & IRQ_TYPE_LEVEL_LOW)
> > > -			value |= PADCFG0_RXINV;
> > > +		rxevcfg = PADCFG0_RXEVCFG_LEVEL;
> > >  	} else {
> > > -		value |= PADCFG0_RXEVCFG_DISABLED <<
> > PADCFG0_RXEVCFG_SHIFT;
> > > +		rxevcfg = PADCFG0_RXEVCFG_DISABLED;
> > >  	}
> > >
> > > +	if (type == IRQ_TYPE_EDGE_FALLING || type ==
> > IRQ_TYPE_LEVEL_LOW)
> > > +		value |= PADCFG0_RXINV;
> > > +
> > > +	value |= rxevcfg << PADCFG0_RXEVCFG_SHIFT;
> > >  	writel(value, reg);
> > 
> > Looking at this I realized that entire temporary variable assignments can be
> > done outside of spin lock. You probably would need another one for keeping
> > rxinv value.
> 
> Something like this?
> 
>         u32 value, rxevcfg;
>         u32 rxinv = 0;
> 
>         if ((type & IRQ_TYPE_EDGE_BOTH) == IRQ_TYPE_EDGE_BOTH) {
>                 rxevcfg = PADCFG0_RXEVCFG_EDGE_BOTH;
>         } else if (type & IRQ_TYPE_EDGE_FALLING) {
>                 rxevcfg = PADCFG0_RXEVCFG_EDGE;
>         } else if (type & IRQ_TYPE_EDGE_RISING) {
>                 rxevcfg = PADCFG0_RXEVCFG_EDGE;
>         } else if (type & IRQ_TYPE_LEVEL_MASK) {
>                 rxevcfg = PADCFG0_RXEVCFG_LEVEL;
>         } else {
>                 rxevcfg = PADCFG0_RXEVCFG_DISABLED;
>         }
> 
>         if (type == IRQ_TYPE_EDGE_FALLING || type == IRQ_TYPE_LEVEL_LOW)
>                 rxinv = PADCFG0_RXINV;
> 
>         raw_spin_lock_irqsave(&pctrl->lock, flags);
> 
>         intel_gpio_set_gpio_mode(reg);
> 
>         value = readl(reg);
> 
>         value &= ~(PADCFG0_RXEVCFG_MASK | PADCFG0_RXINV);
>         value |= rxinv;
>         value |= rxevcfg << PADCFG0_RXEVCFG_SHIFT;
> 
>         writel(value, reg);

This one looks better.

> > Will it give us any memory reduction in comparison to the current code?
> 
> add/remove: 0/0 grow/shrink: 1/0 up/down: 4/0 (4)
> Function                                     old     new   delta
> intel_gpio_irq_type                          317     321      +4
> Total: Before=10469, After=10473, chg +0.04%
> 
> Unfortunately gcc doesn't seem to consider this as best of the sequence,
> and I'm not entirely sure why.

It's fine as is, readability counts more than few bytes here.