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

Russell King (Oracle)
2022-12-08T19:10:45Z

On Thu, Dec 08, 2022 at 07:46:26PM +0100, Robert Jarzmik wrote:
>
> Jonathan Neuschäfer <j.neuschaefer@gmx.net> writes:
>
> > Without further code changes this wouldn't be sufficient, because the
> > pinctrl driver also touches the GPIO direction registers at offset
> > 0x0c-0x14.
>
> Historically, this problem was adressed by a "hack" if I remember correctly,
> as the
> registers do overlap (on pxa27x at least, but I think on pxa25x as well) :
> - GAFR (alternate functions) and GPDR (input or output) are "pinctrl"
> - GPSR, GPCR, GPLR are "gpio" registers
> - the memory map (physical) at 0x40e0 0000 is as Jonathan wrote :
> - 3 u32 GPLR (gpio)
> - 3 u32 GPDR (pinctrl)
> - 3 u32 GPSR (gpio)
> - 3 u32 GPCR (gpio)
>
> The "hack" was that one driver was mapping the area _without_ claiming it
> (this
> is part from memory, I didn't check in the code today). The gpio was
> probably
> the claiming one, while the pinctrl was the "only using one".
>
> As of today, I should have a look what was changed, but I'm pretty sure in
> all
> pxa2xx architecture there is an overlap, as for these ancient platforms the
> pinctrl wasn't yet separated from the gpio IC.
>
> The only was out so far I can see from my head would be to declare multiple
> very small IO ranges :
> - pinctrl pxa25x : 0x40e0 000c (12 bytes), 0x40e0 0054 (32 bytes)
> - pinctrl pxa25x : 0x40e0 000c (12 bytes), 0x40e0 0054 (32 bytes), 0x40e0
> 010c (4 bytes)
> - gpio : from 0x40e0 0000 to 0x40e0 0070 included, without the pinctrl ones
>
> As a general guide, in gpio-pxa.c, you have the table in [1]. Think GPDR and
> GAFR as
> pinctrl, and all the other ones as gpio. Ah and yes, the GAFR ones are
> missing in this
> table.
>
> One last think : in a pre device-tree world, when we didn't had yet the pxa
> pinctrl
> driver, the gpio driver was directly playing with the GPDR registers, fun
> old times.

From a quick look, I think this commit is to blame:

542c25b7a209 drivers: gpio: pxa: use devm_platform_ioremap_resource()

Someone "helpfully" making this change:

- res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
- if (!res)
- return -EINVAL;
- gpio_reg_base = devm_ioremap(&pdev->dev, res->start,
- resource_size(res));
+
+ gpio_reg_base = devm_platform_ioremap_resource(pdev, 0);

which introduces request_mem_region() to the PXA GPIO driver, resulting
in this resource clash.

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