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

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Date:   Thu, 15 Jun 2023 09:48:12 +0000
From:   "Jadav, Raag" <raag.jadav@...el.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
CC:     "linus.walleij@...aro.org" <linus.walleij@...aro.org>,
        "mika.westerberg@...ux.intel.com" <mika.westerberg@...ux.intel.com>,
        "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 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);

> 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.