Re: [PATCH v2] gpio: Device tree support for LPC32xx
From: jonsmirl@xxxxxxxxx
Date: Sat Apr 07 2012 - 13:18:16 EST
On Sat, Apr 7, 2012 at 9:50 AM, Roland Stigge <stigge@xxxxxxxxx> wrote:
> Hi Grant,
>
> thanks for your suggestions about LPC32xx GPIO DT.
>
> Regarding the numbering:
>
> On 07/04/12 05:53, Grant Likely wrote:
>>> +Required properties:
>>> +- compatible: "nxp,lpc32xx-gpio"
>>> +- reg: Physical base address and length of the controller's registers.
>>> +- #address-cells: Always 1, for indexing of the subnodes (GPIO groups of the
>>> + SoC)
>>> +- #size-cells: Always 0
>>> +
>>> +Required properties of sub-nodes which describe the GPIO groups of LPC32xx:
>>> +- gpio-controller: Marks the device node as a GPIO controller.
>>> +- #gpio-cells: Should be two. The first cell is the pin number and the
>>> + second cell is used to specify optional parameters:
>>> + - bit 0 specifies polarity (0 for normal, 1 for inverted)
>>> +- reg: Index of the GPIO group
>>
>> If these are merely contiguous register banks of 32 gpio lines, then
>> established convention is pretty much to only use one node and make
>> the translate function decode bank and bit out of the gpio specifier.
>> There isn't a whole lot of value it having all the sub nodes when
>> there isn't anything significantly different between them.
>
> Please consider how the groups are specified in
> drivers/gpio/gpio-lpc32xx.c. They each have different numbers of lines
> and GPIO / GPI / GPO functionality. So they also have different callback
> sets, and we need to do separate gpiochip_add()s which leads to the
> separate gpio-bank specifications in the dtsi file. Separate enabling of
> those banks via OF are a nice by-product.
When you have six banks of 32b registers with sparse, active GPIOs in
the banks, is there any advantage to saying bank one has 8 gpios, bank
2 has 14, bank 3 has 2, etc in the gpiochip? Or just just register
them as six banks of 32 GPIOs without indicating which are
valid/invalid? Maybe add a way for the DT to indicate the sparse map
of valid GPIOs?
We're introducing a lot of complexity around invalid GPIO numbers that
shouldn't matter in a working system.
LPC31xx is even worse. I have 12 banks of sparse GPIOs.
>
> So I would like to keep it that way.
>
> What do you think?
>
> Thanks in advance,
>
> Roland
>
>>> + gpio: gpio@40028000 {
>>> + compatible = "nxp,lpc32xx-gpio";
>>> + reg = <0x40028000 0x1000>;
>>> + /* create a private address space for enumeration */
>>> + #address-cells = <1>;
>>> + #size-cells = <0>;
>>> +
>>> + gpio_p0: gpio-bank@0 {
>>> + gpio-controller;
>>> + #gpio-cells = <2>;
>>> + reg = <0>;
>>> + };
>>> +
>>> + gpio_p1: gpio-bank@1 {
>>> + gpio-controller;
>>> + #gpio-cells = <2>;
>>> + reg = <1>;
>>> + };
>>> +
>>> + gpio_p2: gpio-bank@2 {
>>> + gpio-controller;
>>> + #gpio-cells = <2>;
>>> + reg = <2>;
>>> + };
>>> +
>>> + gpio_p3: gpio-bank@3 {
>>> + gpio-controller;
>>> + #gpio-cells = <2>;
>>> + reg = <3>;
>>> + };
>>> +
>>> + gpi_p3: gpio-bank@4 {
>>> + gpio-controller;
>>> + #gpio-cells = <2>;
>>> + reg = <4>;
>>> + };
>>> +
>>> + gpo_p3: gpio-bank@5 {
>>> + gpio-controller;
>>> + #gpio-cells = <2>;
>>> + reg = <5>;
>>> + };
>>> + };
>>> --- linux-2.6.orig/arch/arm/mach-lpc32xx/include/mach/gpio.h
>>> +++ linux-2.6/arch/arm/mach-lpc32xx/include/mach/gpio.h
>>> @@ -1 +1,8 @@
>>> -/* empty */
>>> +#ifndef __MACH_GPIO_H
>>> +#define __MACH_GPIO_H
>>> +
>>> +#include "gpio-lpc32xx.h"
>>> +
>>> +#define ARCH_NR_GPIOS (LPC32XX_GPO_P3_GRP + LPC32XX_GPO_P3_MAX)
>>> +
>>> +#endif /* __MACH_GPIO_H */
>>> --- linux-2.6.orig/drivers/gpio/gpio-lpc32xx.c
>>> +++ linux-2.6/drivers/gpio/gpio-lpc32xx.c
>>> @@ -21,6 +21,9 @@
>>> #include <linux/io.h>
>>> #include <linux/errno.h>
>>> #include <linux/gpio.h>
>>> +#include <linux/of_gpio.h>
>>> +#include <linux/platform_device.h>
>>> +#include <linux/module.h>
>>>
>>> #include <mach/hardware.h>
>>> #include <mach/platform.h>
>>> @@ -454,10 +457,55 @@ static struct lpc32xx_gpio_chip lpc32xx_
>>> },
>>> };
>>>
>>> +/* Empty now, can be removed later when mach-lpc32xx is finally switched over
>>> + * to DT support
>>> + */
>>> void __init lpc32xx_gpio_init(void)
>>> {
>>> +}
>>> +
>>> +static int __devinit lpc32xx_gpio_probe(struct platform_device *pdev)
>>> +{
>>> + struct device_node *node;
>>> int i;
>>>
>>> - for (i = 0; i < ARRAY_SIZE(lpc32xx_gpiochip); i++)
>>> - gpiochip_add(&lpc32xx_gpiochip[i].chip);
>>> + if (pdev->dev.of_node) {
>>> + for_each_child_of_node(pdev->dev.of_node, node) {
>>> + if (of_device_is_available(node)) {
>>> + u32 index;
>>> + struct gpio_chip *chip;
>>> + if (of_property_read_u32(node,
>>> + "reg", &index) < 0)
>>> + continue;
>>> + if (index >= ARRAY_SIZE(lpc32xx_gpiochip))
>>> + continue;
>>> + chip = &lpc32xx_gpiochip[index].chip;
>>> + chip->of_node = of_node_get(node);
>>> + gpiochip_add(chip);
>>> + }
>>> + }
>>> + } else {
>>> + for (i = 0; i < ARRAY_SIZE(lpc32xx_gpiochip); i++)
>>> + gpiochip_add(&lpc32xx_gpiochip[i].chip);
>>> + }
>>> +
>>> + return 0;
>>> }
>>> +
>>> +#ifdef CONFIG_OF
>>> +static struct of_device_id lpc32xx_gpio_of_match[] __devinitdata = {
>>> + { .compatible = "nxp,lpc32xx-gpio", },
>>> + { },
>>> +};
>>> +#endif
>>> +
>>> +static struct platform_driver lpc32xx_gpio_driver = {
>>> + .driver = {
>>> + .name = "lpc32xx-gpio",
>>> + .owner = THIS_MODULE,
>>> + .of_match_table = lpc32xx_gpio_of_match,
>>> + },
>>> + .probe = lpc32xx_gpio_probe,
>>> +};
>>> +
>>> +module_platform_driver(lpc32xx_gpio_driver);
>>
>
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--
Jon Smirl
jonsmirl@xxxxxxxxx
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