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Message-ID: <CACRpkdaOQM7=mDTA1K92N5P=jjaCyhsSw5DGL+bnXE_GOYw82Q@mail.gmail.com>
Date: Mon, 9 Jan 2017 20:35:37 +0100
From: Linus Walleij <linus.walleij@...aro.org>
To: David Daney <ddaney.cavm@...il.com>
Cc: Alexandre Courbot <gnurou@...il.com>,
Rob Herring <robh+dt@...nel.org>,
Mark Rutland <mark.rutland@....com>,
"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
David Daney <david.daney@...ium.com>,
Marc Zyngier <marc.zyngier@....com>
Subject: Re: [PATCH v2 2/3] gpio: Add gpio driver support for ThunderX and OCTEON-TX
On Sat, Jan 7, 2017 at 12:22 AM, David Daney <ddaney.cavm@...il.com> wrote:
> From: David Daney <david.daney@...ium.com>
>
> Cavium ThunderX and OCTEON-TX are arm64 based SoCs. Add driver for
> the on-chip GPIO pins.
>
> Signed-off-by: David Daney <david.daney@...ium.com>
(...)
> +config GPIO_THUNDERX
> + tristate "Cavium ThunderX/OCTEON-TX GPIO"
Do you really load this as module? OK then...
> +#include <linux/gpio.h>
No.
#include <linux/gpio/driver.h>
Nothing else.
> +#define GLITCH_FILTER_400NS ((4ull << GPIO_BIT_CFG_FIL_SEL_SHIFT) | \
> + (9ull << GPIO_BIT_CFG_FIL_CNT_SHIFT))
> +
> +static unsigned int bit_cfg_reg(unsigned int line)
> +{
> + return 8 * line + GPIO_BIT_CFG;
> +}
> +
> +static unsigned int intr_reg(unsigned int line)
> +{
> + return 8 * line + GPIO_INTR;
> +}
This looks a bit overzealous, but OK.
> +struct thunderx_gpio;
> +
> +struct thunderx_irqdev {
> + struct thunderx_gpio *gpio;
> + char *name;
> + unsigned int line;
> +};
> +
> +struct thunderx_gpio {
> + struct gpio_chip chip;
> + u8 __iomem *register_base;
> + struct msix_entry *msix_entries;
> + struct thunderx_irqdev *irqdev_entries;
> + raw_spinlock_t lock;
> + unsigned long invert_mask[2];
> + unsigned long od_mask[2];
> + int base_msi;
> +};
Why can't you just move the thunderx_irqdev fields
into thunderx_gpio? It will save very little memory for
non-irq systems, I do not think footprint warrants it.
> +
> +static bool thunderx_gpio_is_gpio(struct thunderx_gpio *gpio,
> + unsigned int line)
> +{
> + u64 bit_cfg = readq(gpio->register_base + bit_cfg_reg(line));
> + bool rv = (bit_cfg & GPIO_BIT_CFG_PIN_SEL_MASK) == 0;
> +
> + WARN_RATELIMIT(!rv, "Pin %d not available for GPIO\n", line);
> +
> + return rv;
> +}
Nifty. So this actually has a pin controller back-end?
I haven't seen the code for that yet, I think.
This seems like a cheap version of
/* External interface to pin control */
extern int pinctrl_request_gpio(unsigned gpio);
extern void pinctrl_free_gpio(unsigned gpio);
extern int pinctrl_gpio_direction_input(unsigned gpio);
extern int pinctrl_gpio_direction_output(unsigned gpio);
>From <linux/pinctrl/consumer.h>
So are you planning pin control support separately in drivers/pinctrl/*
in the future? Maybe some comment to replace this with proper pin control
in the future is warranted?
> +static int thunderx_gpio_dir_in(struct gpio_chip *chip, unsigned int line)
> +{
> + struct thunderx_gpio *gpio = container_of(chip, struct thunderx_gpio, chip);
1. Please use gpiochip_get_data() instead of the container_of() construction,
utilized devm_gpiochip_add_data() in your probe() call.
2. Do not call this local variable "gpio" that is superconfusing, at least call
it txgpio or something.
1 & 2 applies EVERYWHERE in thid driver.
> +static void thunderx_gpio_set(struct gpio_chip *chip, unsigned int line,
> + int value)
> +{
> + struct thunderx_gpio *gpio = container_of(chip, struct thunderx_gpio, chip);
> + int bank = line / 64;
> + int bank_bit = line % 64;
> +
> + void __iomem *reg = gpio->register_base +
> + (bank * GPIO_2ND_BANK) + (value ? GPIO_TX_SET : GPIO_TX_CLR);
> +
> + writeq(1ull << bank_bit, reg);
Use this:
#include <linus/bitops.h>
writeq(BIT(bank_bit), reg);
Applies EVERYWHERE you use (1ULL << n)
> +static int thunderx_gpio_set_single_ended(struct gpio_chip *chip,
> + unsigned int line,
> + enum single_ended_mode mode)
Thanks for implementing this properly.
> + read_bits >>= bank_bit;
> +
> + if (test_bit(line, gpio->invert_mask))
> + return !(read_bits & 1);
> + else
> + return read_bits & 1;
This looks superconvoluted.
Can't you just:
if (test_bit(line, gpio->invert_mask))
return !(read_bits & BIT(bank_bit));
else
return !!(read_bits & BIT(bank_bit));
OK maybe not much clearer but seems clearer to me.
> +static int thunderx_gpio_irq_request_resources(struct irq_data *data)
> +{
> + struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
> + struct thunderx_gpio *gpio = container_of(chip, struct thunderx_gpio, chip);
> + unsigned int line = data->hwirq;
> + struct thunderx_irqdev *irqdev;
> + int err;
> +
> + if (!thunderx_gpio_is_gpio(gpio, line))
> + return -EIO;
> +
> + irqdev = gpio->irqdev_entries + line;
> +
> + irqdev->gpio = gpio;
> + irqdev->line = line;
> + irqdev->name = devm_kasprintf(chip->parent, GFP_KERNEL,
> + "gpio-%d", line + chip->base);
> +
> + writeq(GPIO_INTR_ENA_W1C, gpio->register_base + intr_reg(line));
> +
> + err = devm_request_irq(chip->parent, gpio->msix_entries[line].vector,
> + thunderx_gpio_chain_handler, IRQF_NO_THREAD, irqdev->name, irqdev);
> + return err;
> +}
> +
> +static void thunderx_gpio_irq_release_resources(struct irq_data *data)
> +{
> + struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
> + struct thunderx_gpio *gpio = container_of(chip, struct thunderx_gpio, chip);
> + unsigned int line = data->hwirq;
> + struct thunderx_irqdev *irqdev;
> +
> + irqdev = gpio->irqdev_entries + line;
> +
> + /*
> + * The request_resources/release_resources functions may be
> + * called multiple times in the lifitime of the driver, so we
> + * need to clean up the devm_* things to avoid a resource
> + * leak.
> + */
> + devm_free_irq(chip->parent, gpio->msix_entries[line].vector, irqdev);
> +
> + writeq(GPIO_INTR_ENA_W1C, gpio->register_base + intr_reg(line));
> +
> + devm_kfree(chip->parent, irqdev->name);
> +}
Then just do not use the devm* variants. Explicitly allocate and free instead.
These callbacks should be called on all resources anyways.
> +static void thunderx_gpio_irq_unmask(struct irq_data *data)
> +{
> + struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
> + struct thunderx_gpio *gpio = container_of(chip, struct thunderx_gpio, chip);
> + unsigned int line = data->hwirq;
> +
> + writeq(GPIO_INTR_ENA_W1S, gpio->register_base + intr_reg(line));
> +}
> +
> +static int thunderx_gpio_irq_set_type(struct irq_data *data,
> + unsigned int flow_type)
> +{
> + struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
> + struct thunderx_gpio *gpio = container_of(chip, struct thunderx_gpio, chip);
> + unsigned int line = data->hwirq;
> + u64 bit_cfg;
> +
> + irqd_set_trigger_type(data, flow_type);
> +
> + bit_cfg = GLITCH_FILTER_400NS | GPIO_BIT_CFG_INT_EN;
> +
> + if (flow_type & IRQ_TYPE_EDGE_BOTH) {
> + irq_set_handler_locked(data, handle_edge_irq);
> + bit_cfg |= GPIO_BIT_CFG_INT_TYPE;
> + } else {
> + irq_set_handler_locked(data, handle_level_irq);
> + }
> +
> + raw_spin_lock(&gpio->lock);
> + if (flow_type & (IRQ_TYPE_EDGE_FALLING | IRQ_TYPE_LEVEL_LOW)) {
> + bit_cfg |= GPIO_BIT_CFG_PIN_XOR;
> + set_bit(line, gpio->invert_mask);
> + } else {
> + clear_bit(line, gpio->invert_mask);
> + }
> + clear_bit(line, gpio->od_mask);
> + writeq(bit_cfg, gpio->register_base + bit_cfg_reg(line));
> + raw_spin_unlock(&gpio->lock);
> +
> + return IRQ_SET_MASK_OK;
> +}
> +
> +/*
> + * Interrupts are chained from underlying MSI-X vectors. We have
> + * these irq_chip functions to be able to handle level triggering
> + * semantics and other acknowledgment tasks associated with the GPIO
> + * mechanism.
> + */
> +static struct irq_chip thunderx_gpio_irq_chip = {
> + .name = "GPIO",
> + .irq_enable = thunderx_gpio_irq_unmask,
> + .irq_disable = thunderx_gpio_irq_mask,
> + .irq_ack = thunderx_gpio_irq_ack,
> + .irq_mask = thunderx_gpio_irq_mask,
> + .irq_mask_ack = thunderx_gpio_irq_mask_ack,
> + .irq_unmask = thunderx_gpio_irq_unmask,
> + .irq_set_type = thunderx_gpio_irq_set_type,
> + .irq_request_resources = thunderx_gpio_irq_request_resources,
> + .irq_release_resources = thunderx_gpio_irq_release_resources,
> + .flags = IRQCHIP_SET_TYPE_MASKED
> +};
This looks wrong.
If you're calling devm_request_irq() on *every* *single* *irq* like you
do here, you are dealing with a hieararchical irqdomain, not a linear one,
and GPIOLIB_IRQCHIP may not be used.
Look at drivers/gpio/gpio-xgene-sb.c for inspiration. That is the only
hierarchical GPIO irqdomain I have right now.
Consult Marc Zyngier's IRQ domain lecture if you have time:
https://www.youtube.com/watch?v=YE8cRHVIM4E
If you have ideas how to combine hierarchical irqdomain and GPIOLIB_IRQCHIP
pls help out.
> + gpio->irqdev_entries = devm_kzalloc(dev,
> + sizeof(struct thunderx_irqdev) * ngpio,
> + GFP_KERNEL);
> + if (!gpio->irqdev_entries) {
> + err = -ENOMEM;
> + goto out;
> + }
I think this is overkill. Use hierarchical irqdomain.
Yours,
Linus Walleij
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