linux-kernel - Re: PXA25x: GPIO driver fails probe due to resource conflict with pinctrl driver

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Date:   Fri, 09 Dec 2022 09:55:41 +0100
From:   Robert Jarzmik <robert.jarzmik@...e.fr>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     Robert Jarzmik <robert.jarzmik@...e.fr>,
        Jonathan Neuschäfer 
        <j.neuschaefer@....net>, Andrew Lunn <andrew@...n.ch>,
        linux-arm-kernel@...ts.infradead.org,
        Haojian Zhuang <haojian.zhuang@...il.com>,
        Daniel Mack <daniel@...que.org>, linux-kernel@...r.kernel.org
Subject: Re: PXA25x: GPIO driver fails probe due to resource conflict with
 pinctrl driver


"Russell King (Oracle)" <linux@...linux.org.uk> writes:
> Does the GPIO driver talk to the pinctrl driver to switch GPIOs 
> between
> input and output mode? If it does, that's fine. If not, that can 
> cause
> regressions, as GPIOs may need to be switched between input and 
> output
> mode at runtime (e.g. for I2C gpio-based bitbang).

It does.
Basically it tries pinctrl first, and falls back to direct 
registers
access. Here is a small extract of the gpio direction manipulation 
in
gpio-pxa.c :
	if (pxa_gpio_has_pinctrl()) {
		ret = pinctrl_gpio_direction_output(chip->base + 
		offset);
		if (ret)
			return ret;
	}

	spin_lock_irqsave(&gpio_lock, flags);

	tmp = readl_relaxed(base + GPDR_OFFSET);
        ... blablabal we set the bit, and write back the register.

Cheers.

--
Robert