[RFC 4/4] gpio: sifive: Add GPIO driver for SiFive SoCs

[atish.patra@wdc.com (Atish Patra)]

On 10/10/18 5:35 AM, Linus Walleij wrote:
> Hi Atish,
> 
> thanks for your patch!
> 
> On Tue, Oct 9, 2018 at 8:51 PM Atish Patra <atish.patra@wdc.com> wrote:
> 
>> From: "Wesley W. Terpstra" <wesley@sifive.com>
>>
>> Adds the GPIO driver for SiFive RISC-V SoCs.
>>
>> Signed-off-by: Wesley W. Terpstra <wesley@sifive.com>
>> [Atish: Various fixes and code cleanup]
>> Signed-off-by: Atish Patra <atish.patra@wdc.com>
> 
> (...)
> 
>> +config GPIO_SIFIVE
>> +       bool "SiFive GPIO support"
>> +       depends on OF_GPIO
>> +       select GPIOLIB_IRQCHIP
> 
> I suggest to add
> select GPIO_GENERIC as per below.
> 
> Maybe select REGMAP_MMIO as well.

ok.

> 
>> +       help
>> +         Say yes here to support the GPIO device on SiFive SoCs.
>> +
> 
>> +#include <linux/of_irq.h>
>> +#include <linux/irqchip/chained_irq.h>
> 
> Do you need these two? I think <linux/gpio/driver.h>
> will bring them in for you.
> 

driver.h only brings chained_irq.h. of_irq.h is still required. Right ?

>> +#include <linux/pinctrl/consumer.h>
> 
> Are you using this?

My bad. Left over from the old code. I will remove it.

> 
>> +struct sifive_gpio {
>> +       raw_spinlock_t          lock;
>> +       void __iomem            *base;
>> +       struct gpio_chip        gc;
>> +       unsigned long           enabled;
> 
> Since max GPIO is 32 why not use an u32 for this?
> 

Sure.

>> +       unsigned int            trigger[MAX_GPIO];
>> +       unsigned int            irq_parent[MAX_GPIO];
>> +       struct sifive_gpio      *self_ptr[MAX_GPIO];
>> +};
>> +
>> +static void sifive_assign_bit(void __iomem *ptr, unsigned int offset, int value)
>> +{
>> +       /*
>> +        * It's frustrating that we are not allowed to use the device atomics
>> +        * which are GUARANTEED to be supported by this device on RISC-V
>> +        */
>> +       u32 bit = BIT(offset), old = ioread32(ptr);
>> +
>> +       if (value)
>> +               iowrite32(old | bit, ptr);
>> +       else
>> +               iowrite32(old & ~bit, ptr);
>> +}
> 
> This looks like a mask and set implementation, you are
> essentially reinventing regmap MMIO and the
> regmap_update_bits() call. Could you look into
> just using regmap MMIO in that case?
> 
> If you need examples, look at gpio-mvebu.c that calls
> devm_regmap_init_mmio() for example.
> 

That's really cool. Sorry, for not checking that earlier.
I am pretty new to this.

>> +static int sifive_direction_input(struct gpio_chip *gc, unsigned int offset)
>> +static int sifive_direction_output(struct gpio_chip *gc, unsigned int offset,
>> +static int sifive_get_direction(struct gpio_chip *gc, unsigned int offset)
>> +static int sifive_get_value(struct gpio_chip *gc, unsigned int offset)
>> +static void sifive_set_value(struct gpio_chip *gc, unsigned int offset,
> 
> These functions look like a typical hardware that can use
> 
> GPIOLIB_GENERIC and bgpio_init() to set up the accessors.
> 
> See gpio-ftgpio010.c for an example.
> 
> As a bonus you will get .get/.set_multiple implemented by
> the generic GPIO.
> 

Great. This will reduce the driver a code by a big factor.
Thanks for the pointer.


>> +static void sifive_irq_enable(struct irq_data *d)
>> +static void sifive_irq_disable(struct irq_data *d)
> (...)
>> +static struct irq_chip sifive_irqchip = {
>> +       .name           = "sifive-gpio",
>> +       .irq_set_type   = sifive_irq_set_type,
>> +       .irq_mask       = sifive_irq_mask,
>> +       .irq_unmask     = sifive_irq_unmask,
>> +       .irq_enable     = sifive_irq_enable,
>> +       .irq_disable    = sifive_irq_disable,
> 
> The handling of .irq_enable and .irq_disable has
> changed upstream. Please align with the new codebase
> as changed by Hans Verkuil:
> 
> commit 461c1a7d4733d1dfd5c47b040cf32a5e7eefbc6c
> "gpiolib: override irq_enable/disable"
> commit 4e9439ddacea06f35acce4d374bf6bd0acf99bc8
> "gpiolib: add flag to indicate if the irq is disabled"
> 
> You will need to rebase your work on the v4.20-rc1 once it is
> out. Right now the changes are on linux-next or my devel
> branch.

Will do.

> 
>> +       ngpio = of_irq_count(node);
>> +       if (ngpio >= MAX_GPIO) {
>> +               dev_err(dev, "Too many GPIO interrupts (max=%d)\n", MAX_GPIO);
>> +               return -ENXIO;
>> +       }
> (...)
>> +       for (gpio = 0; gpio < ngpio; ++gpio) {
>> +               irq = platform_get_irq(pdev, gpio);
>> +               if (irq < 0) {
>> +                       dev_err(dev, "invalid IRQ\n");
>> +                       gpiochip_remove(&chip->gc);
>> +                       return -ENODEV;
>> +               }
> 
> This is an hierarchical IRQ so it should use an hierarchical
> irqdomain.
> 
> I am discussing with Thierry to make more generic irq domains
> for hierarchical IRQ GPIOs, until then you have to look at
> gpio-thunderx.c, gpio-uniphier.c or gpio-xgene-sb.c that all
> use hierarchical IRQs.
> 

Thanks. I will convert them to hierarchical IRQ.

Regards,
Atish
> Yours,
> Linus Walleij
>