From: Arnd Bergmann <arnd@arndb.de>
To: monstr@monstr.eu
Cc: balbi@ti.com, Mark Rutland <mark.rutland@arm.com>,
        Subbaraya Sundeep Bhatta <subbaraya.sundeep.bhatta@xilinx.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Subbaraya Sundeep Bhatta <sbhatta@xilinx.com>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>
Subject: Re: [PATCH RFC] usb: gadget: Add xilinx axi usb2 device support
Date: Fri, 21 Feb 2014 17:15:04 +0100
Message-ID: <1684019.mmMhl0O7OE@wuerfel>
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On Friday 21 February 2014 16:51:07 Michal Simek wrote:
> > | 
> > |     if (res->flags & IORESOURCE_CACHEABLE)
> > |             dest_ptr = devm_ioremap(dev, res->start, size);
> > |     else
> > |             dest_ptr = devm_ioremap_nocache(dev, res->start, size);
> 
> I have read it just not sure if IORESOURCE_CACHEABLE is setup by default
> or not.
> If yes, then you have to setup res->flags in your driver and have to
> check it.

ioremap() and ioremap_nocache() are the same on all architectures.
If you want a cacheable mapping, you need to call ioremap_cache(),
which unfortunately doesn't exist on all architectures and also
doesn't have a devm_* variant.

I don't know how the above code made it into devm_ioremap_resource(),
it's clearly bogus. The only time we ever set IORESOURCE_CACHEABLE
is for ROM BARs on PCI, which in turn are rarely used in the kernel.
It's never set for any platform devices, aside from one use
in arch/arm/mach-clps711x/board-cdb89712.c.

	Arnd
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