Re: [PATCH 2/2] of: use platform_device_add

From: Shawn Guo
Date: Sat Feb 16 2013 - 22:03:52 EST

On Fri, Jan 18, 2013 at 01:40:00AM +0000, Grant Likely wrote:
> This allows platform_device_add a chance to call insert_resource on all
> of the resources from OF. At a minimum this fills in proc/iomem and
> presumably makes resource tracking and conflict detection work better.
> However, it has the side effect of moving all OF generated platform
> devices from /sys/devices to /sys/devices/platform/. It /shouldn't/
> break userspace because userspace is not supposed to depend on the full
> path (because userspace always does what it is supposed to, right?).
> This may cause breakage if either:
> 1) any two nodes in a given device tree have overlapping & staggered
> regions (ie. 0x80..0xbf and 0xa0..0xdf; where one is not contained
> within the other). In this case one of the devices will fail to
> register and an exception will be needed in platform_device_add() to
> complain but not fail.


The patch introduce a regression on imx6q boot. The IOMUXC block on
imx6q is special. It acts not only a pin controller but also a system
controller with a bunch of system level registers in there. That's why
we currently have the following two nodes in imx6q device tree with the
same start "reg" address, which work with drivers/mfd/syscon.c and
drivers/pinctrl/pinctrl-imx6q.c respectively.

gpr: iomuxc-gpr@020e0000 {
compatible = "fsl,imx6q-iomuxc-gpr", "syscon";
reg = <0x020e0000 0x38>;

iomuxc: iomuxc@020e0000 {
compatible = "fsl,imx6q-iomuxc";
reg = <0x020e0000 0x4000>;

With the patch in place, pinctrl-imx6q fails to register like below.

syscon 20e0000.iomuxc: syscon regmap start 0x20e0000 end 0x20e3fff registered
imx6q-pinctrl 20e0000.iomuxc: can't request region for resource [mem 0x020e0000-0x020e3fff]
imx6q-pinctrl: probe of 20e0000.iomuxc failed with error -16


> 2) any device calls request_mem_region() on a region larger than
> specified in the device tree. In this case the device node may be
> wrong, or the driver is overreaching. In either case I'd like to know
> about any problems and fix them.

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