linux-kernel - Re: [PATCH 2/2] pinctrl: rockchip: Fix enable/disable/mask/unmask

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Date:	Wed, 19 Nov 2014 09:54:13 -0800
From:	Doug Anderson <dianders@...omium.org>
To:	Heiko Stuebner <heiko@...ech.de>,
	Linus Walleij <linus.walleij@...aro.org>
Cc:	Sonny Rao <sonnyrao@...omium.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Chris Zhong <zyw@...k-chips.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	Doug Anderson <dianders@...omium.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] pinctrl: rockchip: Fix enable/disable/mask/unmask

Hi,

On Tue, Nov 18, 2014 at 3:49 PM, Doug Anderson <dianders@...omium.org> wrote:
> +static void rockchip_irq_disable(struct irq_data *d)
> +{
> +       struct irq_chip_generic *gc = irq_data_get_irq_chip_data(d);
> +       u32 val;
> +
> +       irq_gc_lock(gc);
> +       val = irq_reg_readl(gc, GPIO_INTEN);
> +       irq_reg_writel(gc, val & ~d->mask, GPIO_INTEN);
> +       irq_gc_unlock(gc);
> +}

Off list, Dmitry asked me why I didn't use irq_gc_mask_disable_reg()
and irq_gc_unmask_enable_reg() (AKA why I coded up my own function
here).  Originally I tried to use irq_gc_mask_disable_reg() and
irq_gc_unmask_enable_reg().  ..but they're really not designed to work
in tandem with the irq_gc_mask_set_bit() and irq_gc_mask_clr_bit().

Specifically if you try to use one set of functions for your
mask/unmask and the other for your disable/enable you'll find that
they stomp on each other.  Both functions upkeep the exact same
"mask_cache" variable.

Personally I'm totally baffled by how irq_gc_mask_disable_reg() and
irq_gc_unmask_enable_reg() could actually be sane, but that's maybe a
topic for another discussion.  I say that they don't seem sane because
(it seems to me) that if we have a separate "enable" and "disable"
register in hardware that you'd want to write "1"s to both of them and
also possibly not even have a cache.  The current
irq_gc_mask_disable_reg() doesn't do this.  I'm imagining something
like I think I've seen on STM32 where you're got a 3 registers for
everything: the real register, a "write 1 to set", and a "write 1 to
clear".

-Doug
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