linux-kernel - Re: [PATCH v2] pinctrl/nomadik: make independent of prcmu driver

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Date:	Fri, 09 Nov 2012 10:16:03 -0700
From:	Stephen Warren <swarren@...dotorg.org>
To:	Linus Walleij <linus.walleij@...ricsson.com>
CC:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Anmar Oueja <anmar.oueja@...aro.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Stephen Warren <swarren@...dia.com>,
	Loic Pallardy <loic.pallardy@...com>,
	Jonas Aaberg <jonas.aberg@...ricsson.com>
Subject: Re: [PATCH v2] pinctrl/nomadik: make independent of prcmu driver

On 11/09/2012 03:28 AM, Linus Walleij wrote:
> From: Jonas Aaberg <jonas.aberg@...ricsson.com>
> 
> Currently there are some unnecessary criss-cross
> dependencies between the PRCMU driver in MFD and a lot of
> other drivers, mainly because other drivers need to poke
> around in the PRCM register range.
> 
> In cases like this there are actually just a few select
> registers that the pinctrl driver need to read/modify/write,
> and it turns out that no other driver is actually using
> these registers, so there are no concurrency issues
> whatsoever.
> 
> So: don't let the location of the register range complicate
> things, just poke into these registers directly and skip
> a layer of indirection.
> 
> Take this opportunity to add kerneldoc to the pinctrl
> state container.

> diff --git a/drivers/pinctrl/pinctrl-nomadik.c b/drivers/pinctrl/pinctrl-nomadik.c

> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (res) {
> +		npct->prcm_base = devm_ioremap(&pdev->dev, res->start,
> +					       resource_size(res));
> +		if (!npct->prcm_base) {
> +			dev_err(&pdev->dev,
> +				"failed to ioremap PRCM registers\n");
> +			return -ENOMEM;
> +		}
> +	} else {
> +		dev_info(&pdev->dev,
> +			 "No PRCM base, assume no ALT-Cx control is available\n");
> +	}

Where is "assume no ALT-Cx control is available" implemented; I don't
see anything that uses npct->prcm_base to conditionally enable/block any
features. Is it just assumed that the DT won't contain any entries that
trigger writes to the PRCM registers? That seems fragile; it could cause
a "user"-triggered kernel crash.

Aside from that, this seems fine. Much smaller than V1:-)
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