Re: [PATCH v8 2/2] drivers/gpio: Altera soft IP GPIO driver

[Tien Hock Loh <thloh@altera.com>]

On Thu, 2015-02-05 at 18:54 -0800, Tien Hock Loh wrote:
> On Wed, 2015-01-14 at 10:58 +0100, Linus Walleij wrote:
> > On Wed, Dec 24, 2014 at 9:22 AM,  <thloh@altera.com> wrote:
> > 
> > > From: Tien Hock Loh <thloh@altera.com>
> > >
> > > Adds a new driver for Altera soft GPIO IP. The driver is able to
> > > do read/write and allows GPIO to be a interrupt controller.
> > >
> > > Tested on Altera GHRD on interrupt handling and IO.
> > >
> > > Signed-off-by: Tien Hock Loh <thloh@altera.com>
> > 
> > (...)
> > > +config GPIO_ALTERA
> > > +       tristate "Altera GPIO"
> > > +       depends on OF_GPIO
> > 
> > select GPIOLIB_IRQCHIP
> > 
> > Also, I think (see below)
> > 
> > select GENERIC_GPIO
> > 
> > > +#include <linux/gpio.h>
> > 
> > #include <linux/gpio/driver.h>
> > 
> > should be just fine instead of this old header.
> > 
> > > +#include <linux/init.h>
> > > +#include <linux/interrupt.h>
> > > +#include <linux/io.h>
> > > +#include <linux/irq.h>
> > 
> > Should not be needed.
> > 
> > > +#include <linux/irqchip/chained_irq.h>
> > > +#include <linux/irqdomain.h>
> > 
> > None of these should be needed.
> > 
> > > +#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/basic_mmio_gpio.h>
> > 
> > with GENERIC_GPIO (see below).
> 
> OK
> 
> > > +
> > > +#define ALTERA_GPIO_MAX_NGPIO          32
> > > +#define ALTERA_GPIO_DATA               0x0
> > > +#define ALTERA_GPIO_DIR                        0x4
> > > +#define ALTERA_GPIO_IRQ_MASK           0x8
> > > +#define ALTERA_GPIO_EDGE_CAP           0xc
> > > +
> > > +/**
> > > +* struct altera_gpio_chip
> > > +* @mmchip              : memory mapped chip structure.
> > > +* @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)
> > > +* @mapped_irq          : kernel mapped irq number.
> > > +*/
> > > +struct altera_gpio_chip {
> > > +       struct of_mm_gpio_chip mmchip;
> > > +       spinlock_t gpio_lock;
> > > +       int interrupt_trigger;
> > > +       int mapped_irq;
> > > +};
> > > +
> > > +static void altera_gpio_irq_unmask(struct irq_data *d)
> > > +{
> > > +       struct altera_gpio_chip *altera_gc;
> > > +       struct of_mm_gpio_chip *mm_gc;
> > > +       unsigned long flags;
> > > +       u32 intmask;
> > > +
> > > +       altera_gc = irq_data_get_irq_chip_data(d);
> > > +       mm_gc = &altera_gc->mmchip;
> > > +
> > > +       spin_lock_irqsave(&altera_gc->gpio_lock, flags);
> > > +       intmask = readl(mm_gc->regs + ALTERA_GPIO_IRQ_MASK);
> > > +       /* Set ALTERA_GPIO_IRQ_MASK bit to unmask */
> > > +       intmask |= BIT(irqd_to_hwirq(d));
> > > +       writel(intmask, mm_gc->regs + ALTERA_GPIO_IRQ_MASK);
> > > +       spin_unlock_irqrestore(&altera_gc->gpio_lock, flags);
> > > +}
> > > +
> > > +static void altera_gpio_irq_mask(struct irq_data *d)
> > > +{
> > > +       struct altera_gpio_chip *altera_gc;
> > > +       struct of_mm_gpio_chip *mm_gc;
> > > +       unsigned long flags;
> > > +       u32 intmask;
> > > +
> > > +       altera_gc = irq_data_get_irq_chip_data(d);
> > > +       mm_gc = &altera_gc->mmchip;
> > > +
> > > +       spin_lock_irqsave(&altera_gc->gpio_lock, flags);
> > > +       intmask = readl(mm_gc->regs + ALTERA_GPIO_IRQ_MASK);
> > > +       /* Clear ALTERA_GPIO_IRQ_MASK bit to mask */
> > > +       intmask &= ~BIT(irqd_to_hwirq(d));
> > > +       writel(intmask, mm_gc->regs + ALTERA_GPIO_IRQ_MASK);
> > > +       spin_unlock_irqrestore(&altera_gc->gpio_lock, flags);
> > > +}
> > > +
> > > +static int altera_gpio_irq_set_type(struct irq_data *d,
> > > +                                  unsigned int type)
> > > +{
> > > +       struct altera_gpio_chip *altera_gc = irq_data_get_irq_chip_data(d);
> > > +
> > > +       altera_gc = irq_data_get_irq_chip_data(d);
> > > +
> > > +       if (type == IRQ_TYPE_NONE)
> > > +               return 0;
> > > +       if (type == IRQ_TYPE_LEVEL_HIGH &&
> > > +               altera_gc->interrupt_trigger == IRQ_TYPE_LEVEL_HIGH)
> > > +               return 0;
> > > +       if (type == IRQ_TYPE_EDGE_RISING &&
> > > +               altera_gc->interrupt_trigger == IRQ_TYPE_EDGE_RISING)
> > > +               return 0;
> > > +       if (type == IRQ_TYPE_EDGE_FALLING &&
> > > +               altera_gc->interrupt_trigger == IRQ_TYPE_EDGE_FALLING)
> > > +               return 0;
> > > +       if (type == IRQ_TYPE_EDGE_BOTH &&
> > > +               altera_gc->interrupt_trigger == IRQ_TYPE_EDGE_BOTH)
> > > +               return 0;
> > > +
> > > +       return -EINVAL;
> > > +}
> > 
> > It took me a while to understand this. Write in a comment that
> > this is a hardware that is synthesized for a specific trigger
> > type, and that there is no way to software-configure the
> > trigger type.
> > 
> OK noted. 
> 
> > > +
> > > +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_mask(d);
> > > +}
> > 
> > Instead of those pointless functions just assign
> > the unmask/mask functions in the vtable right below.
> > 
> OK
> 
> > > +
> > > +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,
> > 
> > i.e. here.
> > 
> > > +static int altera_gpio_get(struct gpio_chip *gc, unsigned offset)
> > > +{
> > > +       struct of_mm_gpio_chip *mm_gc;
> > > +
> > > +       mm_gc = to_of_mm_gpio_chip(gc);
> > > +
> > > +       return !!(readl(mm_gc->regs + ALTERA_GPIO_DATA) >> offset);
> > > +}
> > > +
> > > +static void altera_gpio_set(struct gpio_chip *gc, unsigned offset, int value)
> > > +{
> > > +       struct of_mm_gpio_chip *mm_gc;
> > > +       struct altera_gpio_chip *chip;
> > > +       unsigned long flags;
> > > +       unsigned int data_reg;
> > > +
> > > +       mm_gc = to_of_mm_gpio_chip(gc);
> > > +       chip = container_of(mm_gc, struct altera_gpio_chip, mmchip);
> > > +
> > > +       spin_lock_irqsave(&chip->gpio_lock, flags);
> > > +       data_reg = readl(mm_gc->regs + ALTERA_GPIO_DATA);
> > > +       if (value)
> > > +               data_reg |= BIT(offset);
> > > +       else
> > > +               data_reg &= ~BIT(offset);
> > > +       writel(data_reg, mm_gc->regs + ALTERA_GPIO_DATA);
> > > +       spin_unlock_irqrestore(&chip->gpio_lock, flags);
> > > +}
> > > +
> > > +static int altera_gpio_direction_input(struct gpio_chip *gc, unsigned offset)
> > > +{
> > > +       struct of_mm_gpio_chip *mm_gc;
> > > +       struct altera_gpio_chip *chip;
> > > +       unsigned long flags;
> > > +       unsigned int gpio_ddr;
> > > +
> > > +       mm_gc = to_of_mm_gpio_chip(gc);
> > > +       chip = container_of(mm_gc, struct altera_gpio_chip, mmchip);
> > > +
> > > +       spin_lock_irqsave(&chip->gpio_lock, flags);
> > > +       /* Set pin as input, assumes software controlled IP */
> > > +       gpio_ddr = readl(mm_gc->regs + ALTERA_GPIO_DIR);
> > > +       gpio_ddr &= ~BIT(offset);
> > > +       writel(gpio_ddr, mm_gc->regs + ALTERA_GPIO_DIR);
> > > +       spin_unlock_irqrestore(&chip->gpio_lock, flags);
> > > +
> > > +       return 0;
> > > +}
> > > +
> > > +static int altera_gpio_direction_output(struct gpio_chip *gc,
> > > +               unsigned offset, int value)
> > > +{
> > > +       struct of_mm_gpio_chip *mm_gc;
> > > +       struct altera_gpio_chip *chip;
> > > +       unsigned long flags;
> > > +       unsigned int data_reg, gpio_ddr;
> > > +
> > > +       mm_gc = to_of_mm_gpio_chip(gc);
> > > +       chip = container_of(mm_gc, struct altera_gpio_chip, mmchip);
> > > +
> > > +       spin_lock_irqsave(&chip->gpio_lock, flags);
> > > +       /* Sets the GPIO value */
> > > +       data_reg = readl(mm_gc->regs + ALTERA_GPIO_DATA);
> > > +       if (value)
> > > +               data_reg |= BIT(offset);
> > > +       else
> > > +               data_reg &= ~BIT(offset);
> > > +       writel(data_reg, mm_gc->regs + ALTERA_GPIO_DATA);
> > > +
> > > +       /* Set pin as output, assumes software controlled IP */
> > > +       gpio_ddr = readl(mm_gc->regs + ALTERA_GPIO_DIR);
> > > +       gpio_ddr |= BIT(offset);
> > > +       writel(gpio_ddr, mm_gc->regs + ALTERA_GPIO_DIR);
> > > +       spin_unlock_irqrestore(&chip->gpio_lock, flags);
> > > +
> > > +       return 0;
> > > +}
> > 
> > These calls seem like pretty vanilla generic GPIO functions.
> > Use GENERIC_GPIO with bgpio_init() and override the default
> > functions only when really needed.
> > 
> > See e.g. drivers/gpio/gpio-74xx-mmio.c
> > 
> OK, I'll update this.

I just recall that I couldn't use bgpio because the number of gpio pins
is configurable and may not be multiple of 8, thus I'll not be updating
this to use bgpio. 

> 
> > > +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);
> > > +
> > > +       return 0;
> > > +}
> > > +
> > > +static const struct irq_domain_ops altera_gpio_irq_ops = {
> > > +       .map    = altera_gpio_irq_map,
> > > +       .xlate = irq_domain_xlate_onecell,
> > > +};
> > 
> > This looks like some leftover garbage. You don't need them with
> > GPIOLIB_IRQCHIP so delete these two.
> > 
> OK
> 
> > > +static int altera_gpio_remove(struct platform_device *pdev)
> > > +{
> > > +       struct altera_gpio_chip *altera_gc = platform_get_drvdata(pdev);
> > > +
> > > +       gpiochip_remove(&altera_gc->mmchip.gc);
> > > +
> > > +       irq_set_handler_data(altera_gc->mapped_irq, NULL);
> > > +       irq_set_chained_handler(altera_gc->mapped_irq, NULL);
> > 
> > These two calls should not be needed either.
> > 
> OK
> 
> > Yours,
> > Linus Walleij
> 
> Regards,
> Tien Hock Loh

Regards,
Tien Hock Loh