linux-kernel - Re: [PATCH for 4.12] Revert "pinctrl: rockchip: avoid hardirq-unsafe functions in irq

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Date:   Tue, 27 Jun 2017 15:06:26 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Brian Norris <briannorris@...omium.org>
cc:     Heiko Stuebner <heiko@...ech.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-rockchip@...ts.infradead.org,
        Julia Cartwright <julia@...com>,
        LKML <linux-kernel@...r.kernel.org>, linux-gpio@...r.kernel.org,
        John Keeping <john@...anate.com>, linux-pm@...r.kernel.org,
        Doug Anderson <dianders@...omium.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tony Lindgren <tony@...mide.com>,
        "David.Wu" <david.wu@...k-chips.com>,
        '黄涛' <huangtao@...k-chips.com>
Subject: Re: [PATCH for 4.12] Revert "pinctrl: rockchip: avoid hardirq-unsafe
 functions in irq_chip"

On Tue, 27 Jun 2017, Thomas Gleixner wrote:
> That aside, looking at the commit which caused this discussion:
> 
> 88bb94216f59e pinctrl: rockchip: avoid hardirq-unsafe functions in irq_chip
> 
> I assume (the changelog lacks details) that the patch want's to avoid a
> might sleep splat from the irq callbacks caused by the regmap spinlock,
> which gets converted into a sleeping lock on RT. It does this by abusing
> the irq_bus_lock() mechanism, which is wrong to begin with.
> 
> The only irq chip function which uses the regmap magic is the
> irq_set_type() callback. Now, I have a hard time to understand (though I'm
> no regmap/pinctrl expert) why that regmap stuff needs to be called in the
> first place. The level and the polarity are programmed via:
> 
>         writel_relaxed(level, gc->reg_base + GPIO_INTTYPE_LEVEL);
>         writel_relaxed(polarity, gc->reg_base + GPIO_INT_POLARITY);
> 
> Why needs the regmap machinery to be invoked there? The GPIO is already
> muxed and configured as interrupt, otherwise none of the irq functions
> could be invoked. Hmm?

That said, the commit should be reverted and the issue needs to analyzed
proper. We still need the RCU -> SCRU conversion, but that's a different
problem.

Thanks,

	tglx