Re: [PATCH V7 1/1] drivers/gpio: Altera soft IP GPIO driver and devicetree binding

[Tien Hock Loh]

On Fri, Mar 7, 2014 at 11:14 PM, Josh Cartwright <joshc@xxxxxxxxxxxxxx> wrote:
> On Mon, Mar 03, 2014 at 06:27:43PM +0800, thloh@xxxxxxxxxx wrote:
>> From: Tien Hock Loh <thloh@xxxxxxxxxx>
>>
>> Add driver support for Altera GPIO soft IP, including interrupts and I/O.
>> Tested on Altera CV SoC board using dipsw and LED using LED framework.
>>
>> Signed-off-by: Tien Hock Loh <thloh@xxxxxxxxxx>
>> ---
>>  .../devicetree/bindings/gpio/gpio-altera.txt       |  44 +++
>>  drivers/gpio/Kconfig                               |   7 +
>>  drivers/gpio/Makefile                              |   1 +
>>  drivers/gpio/gpio-altera.c                         | 419 +++++++++++++++++++++
>>  4 files changed, 471 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/gpio/gpio-altera.txt
>>  create mode 100644 drivers/gpio/gpio-altera.c
>>
>> diff --git a/Documentation/devicetree/bindings/gpio/gpio-altera.txt b/Documentation/devicetree/bindings/gpio/gpio-altera.txt
>> new file mode 100644
>> index 0000000..1de1f9b
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/gpio/gpio-altera.txt
>> @@ -0,0 +1,44 @@
>> +Altera GPIO controller bindings
>> +
>> +Required properties:
>> +- compatible:
>> +  - "altr,pio-1.0"
>> +- reg: Physical base address and length of the controller's registers.
>> +- #gpio-cells : Should be 1
>> +  - The first cell is the gpio offset number
>> +- gpio-controller : Marks the device node as a GPIO controller.
>> +- #interrupt-cells : Should be 1.
>> +  - The first cell is the GPIO offset number within the GPIO controller.
>> +- interrupts: Specify the interrupt.
>> +- interrupt-controller: Mark the device node as an interrupt controller
>> +
>> +Altera GPIO specific required properties:
>> +- altr,interrupt_trigger: Specifies the interrupt trigger type the GPIO
>> +  hardware is synthesized. This field is required if the Altera GPIO controller
>> +  used has IRQ enabled as the interrupt type is not software controlled,
>> +  but hardware synthesized. Required if GPIO is used as an interrupt
>> +  controller. The value is defined in <dt-bindings/interrupt-controller/irq.h>
>> +  Only the following flags are supported:
>> +    IRQ_TYPE_EDGE_RISING
>> +    IRQ_TYPE_EDGE_FALLING
>> +    IRQ_TYPE_EDGE_BOTH
>> +    IRQ_TYPE_LEVEL_HIGH
>
> I'd suggest "altr,interrupt-trigger" (with a hyphen).  So, if I'm
> understanding properly, this controller doesn't support per-gpio trigger
> settings?

Okay, I'll change it to interrupt-trigger. Yes, the hardware doesn't
support per-gpio trigger.

>
> Low-level triggered interrupts aren't supported?

Yes, the hardware controller doesn't support it.

>
>> +
>> +Altera GPIO specific optional properties:
>> +- altr,gpio-bank-width: Width of the GPIO bank. This defines how many pins the
>> +  GPIO device has. Ranges between 1-32. Optional and defaults to 32 is not
>> +  specified.
>
> Generally, this is called 'ngpio', I think.  Might be nice to stay
> consistent with other bindings.

Noted. Thanks.

>
>> +
>> +Example:
>> +
>> +gpio_altr: gpio@40000 {
>> +    compatible = "altr,pio-1.0";
>> +    reg = <0xff200000 0x10>;
>> +    interrupts = <0 45 4>;
>> +    altr,gpio-bank-width = <32>;
>> +    altr,interrupt_trigger = <IRQ_TYPE_EDGE_RISING>;
>> +    #gpio-cells = <1>;
>> +    gpio-controller;
>> +    #interrupt-cells = <1>;
>> +    interrupt-controller;
>> +};
>> diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
>> index 6973387..07bccdf 100644
>> --- a/drivers/gpio/Kconfig
>> +++ b/drivers/gpio/Kconfig
>> @@ -128,6 +128,13 @@ config GPIO_GENERIC_PLATFORM
>>       help
>>         Say yes here to support basic platform_device memory-mapped GPIO controllers.
>>
>> +config GPIO_ALTERA
>> +       tristate "Altera GPIO"
>> +       select IRQ_DOMAIN
>> +       depends on OF_GPIO
>> +       help
>> +         Say yes here to support the Altera PIO device.
>
> nit: you should use tabs for indentation instead of spaces to stay
> consistent.

OK.

>
>> +
>>  config GPIO_IT8761E
>>       tristate "IT8761E GPIO support"
>>       depends on X86  # unconditional access to IO space.
>> diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
>> index 5d50179..88374d2 100644
>> --- a/drivers/gpio/Makefile
>> +++ b/drivers/gpio/Makefile
>> @@ -14,6 +14,7 @@ obj-$(CONFIG_GPIO_74X164)   += gpio-74x164.o
>>  obj-$(CONFIG_GPIO_ADNP)              += gpio-adnp.o
>>  obj-$(CONFIG_GPIO_ADP5520)   += gpio-adp5520.o
>>  obj-$(CONFIG_GPIO_ADP5588)   += gpio-adp5588.o
>> +obj-$(CONFIG_GPIO_ALTERA)    += gpio-altera.o
>>  obj-$(CONFIG_GPIO_AMD8111)   += gpio-amd8111.o
>>  obj-$(CONFIG_GPIO_ARIZONA)   += gpio-arizona.o
>>  obj-$(CONFIG_GPIO_BCM_KONA)  += gpio-bcm-kona.o
>> diff --git a/drivers/gpio/gpio-altera.c b/drivers/gpio/gpio-altera.c
>> new file mode 100644
>> index 0000000..ab0738f
>> --- /dev/null
>> +++ b/drivers/gpio/gpio-altera.c
>> @@ -0,0 +1,419 @@
>> +/*
>> + * Copyright (C) 2013 Altera Corporation
>> + * Based on gpio-mpc8xxx.c
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License as published by
>> + * the Free Software Foundation; either version 2 of the License, or
>> + * (at your option) any later version.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> + * GNU General Public License for more details.
>> + *
>> + * You should have received a copy of the GNU General Public License
>> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
>> + */
>> +
>> +#include <linux/gpio.h>
>> +#include <linux/init.h>
>> +#include <linux/irqdomain.h>
>> +#include <linux/interrupt.h>
>> +#include <linux/io.h>
>> +#include <linux/irq.h>
>> +#include <linux/kernel.h>
>> +#include <linux/module.h>
>> +#include <linux/of_irq.h>
>> +#include <linux/of_gpio.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/slab.h>
>> +
>> +#include <linux/irqchip/chained_irq.h>
>> +
>> +#define ALTERA_GPIO_DATA             0x0
>> +#define ALTERA_GPIO_DIR                      0x4
>> +#define ALTERA_GPIO_IRQ_MASK         0x8
>> +#define ALTERA_GPIO_EDGE_CAP         0xc
>> +#define ALTERA_GPIO_OUTSET           0x10
>> +#define ALTERA_GPIO_OUTCLEAR         0x14
>> +
>> +/**
>> +* struct altera_gpio_chip
>> +* @mmchip            : memory mapped chip structure.
>> +* @irq                       : irq domain that this driver is registered to.
>
> s/@irq/@domain/ ?
>
Yes missed this sorry.

>> +* @gpio_lock         : synchronization lock so that new irq/set/get requests
>> +                       will be blocked until the current one completes.
>> +* @interrupt_trigger : specifies the hardware configured IRQ trigger type
>> +                       (rising, falling, both, high)
>
> @edge_type?
>
Oh, a stray. I'll remove this.

>> +* @mapped_irq                : kernel mapped irq number.
>> +*/
>> +struct altera_gpio_chip {
>> +     struct of_mm_gpio_chip mmchip;
>
> I had never really looked into of_mm_gpio_chip before but...does this
> really get you anything?  All it does is manage mapping your registers
> for you; as far as I can tell it's just another layer of indirection
> with no gain.
>
> I'd suggest lifting 'regs' and 'chip' directly into your
> altera_gpio_chip:
>
>         struct altera_gpio_chip {
>                 struct gpio_chip chip;
>                 struct irq_domain *domain;
>                 void __iomem *regs;
>                 spinlock_t gpio_lock;
>                 int mapped_irq;
>         };
>
> [..]
>

The variable is used in the helper function of_mm_gpiochip_add() for
general memory mapped gpio to reduce code duplications. A lot of the
memory mapped GPIO driver uses this, I just refers to them. Please let
me know if you strongly feel otherwise.

>> +static unsigned int altera_gpio_irq_startup(struct irq_data *d)
>> +{
>> +     altera_gpio_irq_unmask(d);
>> +
>> +     return 0;
>> +}
>> +
>> +static void altera_gpio_irq_shutdown(struct irq_data *d)
>> +{
>> +     altera_gpio_irq_unmask(d);
>> +}
>
> Should you really even be touching masks in startup/shutdown?
>

I'm referring from other GPIO drivers and that's what they do. I do
make a mistake by unmasking the PIOs during shutdown. I'll fix this.

>> +static struct irq_chip altera_irq_chip = {
>> +     .name           = "altera-gpio",
>> +     .irq_mask       = altera_gpio_irq_mask,
>> +     .irq_unmask     = altera_gpio_irq_unmask,
>> +     .irq_set_type   = altera_gpio_irq_set_type,
>> +     .irq_startup    = altera_gpio_irq_startup,
>> +     .irq_shutdown   = altera_gpio_irq_shutdown,
>> +};
>> +
> [..]
>> +static int altera_gpio_to_irq(struct gpio_chip *gc, unsigned offset)
>> +{
>> +     struct of_mm_gpio_chip *mm_gc = to_of_mm_gpio_chip(gc);
>> +     struct altera_gpio_chip *altera_gc = container_of(mm_gc,
>> +                             struct altera_gpio_chip, mmchip);
>> +
>> +     if (!altera_gc->domain)
>> +             return -ENXIO;
>
> How could this happen (hint, move your domain creation before
> gpiochip_add).

Noted. Thanks.

>
>> +     if (offset < altera_gc->mmchip.gc.ngpio)
>> +             return irq_find_mapping(altera_gc->domain, offset);
>> +     else
>> +             return -ENXIO;
>> +}
>> +
>> +static void altera_gpio_irq_handler(unsigned int irq, struct irq_desc *desc)
>> +{
>> +     struct altera_gpio_chip *altera_gc = irq_desc_get_handler_data(desc);
>> +     struct irq_chip *chip = irq_desc_get_chip(desc);
>> +     struct of_mm_gpio_chip *mm_gc = &altera_gc->mmchip;
>> +     unsigned long status;
>> +
>> +     int i;
>> +
>> +     chained_irq_enter(chip, desc);
>> +     /* Handling for level trigger and edge trigger is different */
>> +     if (altera_gc->interrupt_trigger == IRQ_TYPE_LEVEL_HIGH) {
>
> Suggestion: split this into two handling functions, install
> one-or-the-other in your probe() based on the "altr,trigger-type"
> property.  Bonus points: remove interrupt_trigger member from
> altera_gpio_chip entirely.
>

Good point. I'll implement this. However I don't think I can remove
interrupt_trigger from altera_gpio_chip since when doing
altera_gpio_irq_set_type we still need the variable to determine if we
can set the type requested by the user.

>> +             status = readl_relaxed(mm_gc->regs + ALTERA_GPIO_DATA);
>> +             status &= readl_relaxed(mm_gc->regs + ALTERA_GPIO_IRQ_MASK);
>> +
>> +             for (i = 0; i < mm_gc->gc.ngpio; i++) {
>> +                     if (status & BIT(i)) {
>> +                             generic_handle_irq(irq_find_mapping(
>> +                                     altera_gc->domain, i));
>> +                     }
>> +             }
>
> You may find for_each_set_bit() handy.
>

Good point. Will implement. Thanks.

>> +     } else {
>> +             while ((status =
>> +                     (readl_relaxed(mm_gc->regs + ALTERA_GPIO_EDGE_CAP) &
>> +                     readl_relaxed(mm_gc->regs + ALTERA_GPIO_IRQ_MASK)))) {
>> +                     writel_relaxed(status,
>> +                             mm_gc->regs + ALTERA_GPIO_EDGE_CAP);
>> +                     for (i = 0; i < mm_gc->gc.ngpio; i++) {
>> +                             if (status & BIT(i)) {
>> +                                     generic_handle_irq(irq_find_mapping(
>> +                                             altera_gc->domain, i));
>> +                             }
>> +                     }
>> +             }
>> +     }
>> +
>> +     chained_irq_exit(chip, desc);
>> +}
>> +
>> +static int altera_gpio_irq_map(struct irq_domain *h, unsigned int irq,
>> +                             irq_hw_number_t hw_irq_num)
>> +{
>> +     irq_set_chip_data(irq, h->host_data);
>> +     irq_set_chip_and_handler(irq, &altera_irq_chip, handle_level_irq);
>> +     irq_set_irq_type(irq, IRQ_TYPE_NONE);
>
> Does irq_set_irq_type(irq, IRQ_TYPE_NONE) even do anything meaningful here?
>

I'll remove this.

>> +
>> +     return 0;
>> +}
>> +
>> +static struct irq_domain_ops altera_gpio_irq_ops = {
>
> const?
>

I'll add this.

>> +     .map    = altera_gpio_irq_map,
>> +     .xlate = irq_domain_xlate_onecell,
>> +};
>> +
>> +int altera_gpio_probe(struct platform_device *pdev)
>> +{
>> +     struct device_node *node = pdev->dev.of_node;
>> +     int i, id, reg, ret;
>> +     struct altera_gpio_chip *altera_gc = devm_kzalloc(&pdev->dev,
>> +                             sizeof(*altera_gc), GFP_KERNEL);
>> +     if (altera_gc == NULL) {
>> +             pr_err("%s: out of memory\n", node->full_name);
>
> This print is not necessary, as the allocator will complain loudly on
> your behalf.  Also, I'd suggest you not define and initialize
> 'altera_gc' on the same line.

Noted.

>
>> +             return -ENOMEM;
>> +     }
>> +     altera_gc->domain = 0;
>> +
>> +     spin_lock_init(&altera_gc->gpio_lock);
>> +
>> +     id = pdev->id;
>> +
>> +     if (of_property_read_u32(node, "altr,gpio-bank-width", &reg))
>> +             /*By default assume full GPIO controller*/
>> +             altera_gc->mmchip.gc.ngpio = 32;
>> +     else
>> +             altera_gc->mmchip.gc.ngpio = reg;
>> +
>> +     if (altera_gc->mmchip.gc.ngpio > 32) {
>> +             dev_warn(&pdev->dev,
>> +                     "ngpio is greater than 32, defaulting to 32\n");
>> +             altera_gc->mmchip.gc.ngpio = 32;
>> +     }
>> +
>> +     altera_gc->mmchip.gc.direction_input    = altera_gpio_direction_input;
>> +     altera_gc->mmchip.gc.direction_output   = altera_gpio_direction_output;
>> +     altera_gc->mmchip.gc.get                = altera_gpio_get;
>> +     altera_gc->mmchip.gc.set                = altera_gpio_set;
>> +     altera_gc->mmchip.gc.to_irq             = altera_gpio_to_irq;
>> +     altera_gc->mmchip.gc.owner              = THIS_MODULE;
>> +
>> +     ret = of_mm_gpiochip_add(node, &altera_gc->mmchip);
>> +     if (ret) {
>> +             dev_err(&pdev->dev, "Failed adding memory mapped gpiochip\n");
>> +             return ret;
>> +     }
>> +
>> +     platform_set_drvdata(pdev, altera_gc);
>> +
>> +     altera_gc->mapped_irq = irq_of_parse_and_map(node, 0);
>>
>
> platform_get_irq(pdev, 0);
>
OK.

>> +
>> +     if (!altera_gc->mapped_irq)
>> +             goto skip_irq;
>> +
>> +     altera_gc->domain = irq_domain_add_linear(node,
>> +             altera_gc->mmchip.gc.ngpio, &altera_gpio_irq_ops, altera_gc);
>> +
>> +     if (!altera_gc->domain) {
>> +             ret = -ENODEV;
>> +             goto dispose_irq;
>> +     }
>> +
>> +     for (i = 0; i < altera_gc->mmchip.gc.ngpio; i++)
>> +             irq_create_mapping(altera_gc->domain, i);
>> +
>> +     if (of_property_read_u32(node, "altr,interrupt_type", &reg)) {
>> +             ret = -EINVAL;
>> +             dev_err(&pdev->dev,
>> +                     "altr,interrupt_type value not set in device tree\n");
>> +             goto teardown;
>> +     }
>> +     altera_gc->interrupt_trigger = reg;
>> +
>> +     irq_set_handler_data(altera_gc->mapped_irq, altera_gc);
>> +     irq_set_chained_handler(altera_gc->mapped_irq, altera_gpio_irq_handler);
>> +
>> +     return 0;
>> +
>> +teardown:
>> +     irq_domain_remove(altera_gc->domain);
>> +dispose_irq:
>> +     irq_dispose_mapping(altera_gc->mapped_irq);
>> +     WARN_ON(gpiochip_remove(&altera_gc->mmchip.gc) < 0);
>> +
>> +     pr_err("%s: registration failed with status %d\n",
>> +             node->full_name, ret);
>> +
>> +     return ret;
>> +skip_irq:
>> +     return 0;
>> +}
>> +
>> +static int altera_gpio_remove(struct platform_device *pdev)
>> +{
>> +     unsigned int irq, i;
>> +     int status;
>> +     struct altera_gpio_chip *altera_gc = platform_get_drvdata(pdev);
>> +
>> +     status = gpiochip_remove(&altera_gc->mmchip.gc);
>> +
>> +     if (status < 0)
>> +             return status;
>> +
>> +     if (altera_gc->domain) {
>
> How could this happen?
>

Must be me getting overlay paranoid. I'll remove this.

>> +             irq_dispose_mapping(altera_gc->mapped_irq);
>
> Does irq_domain_remove() not teardown mappings?

The irq_domain_remove states that caller has to ensure all mapping has
been disposed prior to calling the function.

>> +
>> +             for (i = 0; i < altera_gc->mmchip.gc.ngpio; i++) {
>> +                     irq = irq_find_mapping(altera_gc->domain, i);
>> +                     if (irq > 0)
>> +                             irq_dispose_mapping(irq);
>> +             }
>> +
>> +             irq_domain_remove(altera_gc->domain);
>> +     }
>> +
>> +     irq_set_handler_data(altera_gc->mapped_irq, NULL);
>> +     irq_set_chained_handler(altera_gc->mapped_irq, NULL);
>> +     return -EIO;
>> +}
>> +
>> +static struct of_device_id altera_gpio_of_match[] = {
>
> const?
>
OK.

>> +     { .compatible = "altr,pio-1.0", },
>> +     {},
>> +};
>> +MODULE_DEVICE_TABLE(of, altera_gpio_of_match);
>> +
>> +static struct platform_driver altera_gpio_driver = {
>> +     .driver = {
>> +             .name   = "altera_gpio",
>> +             .owner  = THIS_MODULE,
>> +             .of_match_table = of_match_ptr(altera_gpio_of_match),
>> +     },
>> +     .probe          = altera_gpio_probe,
>> +     .remove         = altera_gpio_remove,
>> +};
>> +
>> +static int __init altera_gpio_init(void)
>> +{
>> +     return platform_driver_register(&altera_gpio_driver);
>> +}
>> +subsys_initcall(altera_gpio_init);
>> +
>> +static void __exit altera_gpio_exit(void)
>> +{
>> +     platform_driver_unregister(&altera_gpio_driver);
>> +}
>> +module_exit(altera_gpio_exit);
>> +
>> +MODULE_AUTHOR("Tien Hock Loh <thloh@xxxxxxxxxx>");
>> +MODULE_DESCRIPTION("Altera GPIO driver");
>> +MODULE_LICENSE("GPL");
>
> --
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
> hosted by The Linux Foundation
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