linux-kernel - Re: [PATCH v1 3/5] pinctrl: st: Add software edge trigger interrupt support.

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Date:	Wed, 15 Jan 2014 15:27:24 +0100
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Srinivas KANDAGATLA <srinivas.kandagatla@...com>
Cc:	Rob Herring <robh+dt@...nel.org>, Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Rob Landley <rob@...dley.net>,
	Russell King <linux@....linux.org.uk>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v1 3/5] pinctrl: st: Add software edge trigger interrupt support.

On Tue, Jan 14, 2014 at 3:52 PM,  <srinivas.kandagatla@...com> wrote:

> From: Srinivas Kandagatla <srinivas.kandagatla@...com>
>
> ST pin controller does not have hardware support for detecting edge
> triggered interrupts, It only has level triggering support.
> This patch attempts to fake up edge triggers from hw level trigger
> support in software. With this facility now the gpios can be easily used
> for keypads, otherwise it would be difficult for drivers like keypads to
> work with level trigger interrupts.
>
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...com>

Clever! Mostly I like the patch as it is but:

>         for_each_set_bit(n, &port_active, BITS_PER_LONG) {
> +               /* check if we are detecting fake edges ... */
> +               pin_edge_cfg = ST_IRQ_EDGE_CONF(bank_edge_mask, n);
> +
> +               if (pin_edge_cfg) {
> +                       /* edge detection. */
> +                       val = st_gpio_get(&bank->gpio_chip, n);
> +                       if (val)
> +                               writel(BIT(n), bank->base + REG_PIO_SET_PCOMP);
> +                       else
> +                               writel(BIT(n), bank->base + REG_PIO_CLR_PCOMP);
> +
> +                       if (pin_edge_cfg != ST_IRQ_EDGE_BOTH &&
> +                               !((pin_edge_cfg & ST_IRQ_EDGE_FALLING) ^ val))
> +                                       continue;
> +               }
> +

Please insert comments here to explain what you are actually doing
because I sure as hell do not understand this code without comments
describing the trick used.

Yours,
Linus Walleij
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