RE: [PATCH v1 1/1] gpio: add driver for Mellanox BlueField GPIO controller

From: Shravan Ramani
Date: Tue Feb 19 2019 - 15:55:05 EST

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Thank you for the feedback. Regarding the suggested use of regmap mmio, all of the registers being accessed here are 64-bit and the regmap_update_bits/regmap_read/regmap_write calls aren't very convenient to use in this case. All other comments have been addressed in v2.

Regards,
Shravan Kumar Ramani

-----Original Message-----
From: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
Sent: Friday, February 15, 2019 3:48 AM
To: Shravan Ramani <sramani@xxxxxxxxxxxx>
Cc: Linus Walleij <linus.walleij@xxxxxxxxxx>; linux-gpio <linux-gpio@xxxxxxxxxxxxxxx>; LKML <linux-kernel@xxxxxxxxxxxxxxx>
Subject: Re: [PATCH v1 1/1] gpio: add driver for Mellanox BlueField GPIO controller

czw., 14 lut 2019 o 22:30 Shravan Kumar Ramani <sramani@xxxxxxxxxxxx>
napisaÅ(a):
>
> This patch adds support for the GPIO controller used by Mellanox
> BlueField SOCs.
>
> Reviewed-by: David Woods <dwoods@xxxxxxxxxxxx>
> Signed-off-by: Shravan Kumar Ramani <sramani@xxxxxxxxxxxx>
> ---
> drivers/gpio/Kconfig | 7 ++
> drivers/gpio/Makefile | 1 +
> drivers/gpio/gpio-mlxbf.c | 287
> ++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 295 insertions(+)
> create mode 100644 drivers/gpio/gpio-mlxbf.c
>
> diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig index
> b5a2845..2bebe92 100644
> --- a/drivers/gpio/Kconfig
> +++ b/drivers/gpio/Kconfig
> @@ -1292,6 +1292,13 @@ config GPIO_MERRIFIELD
> help
> Say Y here to support Intel Merrifield GPIO.
>
> +config GPIO_MLXBF
> + tristate "Mellanox BlueField SoC GPIO"
> + depends on (MELLANOX_PLATFORM && ARM64 && ACPI) || COMPILE_TEST
> + select GPIO_GENERIC

You're not really depending on it.

> + help
> + Say Y here if you want GPIO support on Mellanox BlueField SoC.
> +
> config GPIO_ML_IOH
> tristate "OKI SEMICONDUCTOR ML7213 IOH GPIO support"
> depends on X86 || COMPILE_TEST diff --git
> a/drivers/gpio/Makefile b/drivers/gpio/Makefile index 37628f8..8d54279
> 100644
> --- a/drivers/gpio/Makefile
> +++ b/drivers/gpio/Makefile
> @@ -83,6 +83,7 @@ obj-$(CONFIG_GPIO_MENZ127) += gpio-menz127.o
> obj-$(CONFIG_GPIO_MERRIFIELD) += gpio-merrifield.o
> obj-$(CONFIG_GPIO_MC33880) += gpio-mc33880.o
> obj-$(CONFIG_GPIO_MC9S08DZ60) += gpio-mc9s08dz60.o
> +obj-$(CONFIG_GPIO_MLXBF) += gpio-mlxbf.o
> obj-$(CONFIG_GPIO_ML_IOH) += gpio-ml-ioh.o
> obj-$(CONFIG_GPIO_MM_LANTIQ) += gpio-mm-lantiq.o
> obj-$(CONFIG_GPIO_MOCKUP) += gpio-mockup.o
> diff --git a/drivers/gpio/gpio-mlxbf.c b/drivers/gpio/gpio-mlxbf.c new
> file mode 100644 index 0000000..e5c50db
> --- /dev/null
> +++ b/drivers/gpio/gpio-mlxbf.c
> @@ -0,0 +1,287 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/acpi.h>
> +#include <linux/bitops.h>
> +#include <linux/device.h>
> +#include <linux/gpio/driver.h>
> +#include <linux/io.h>
> +#include <linux/ioport.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/moduleparam.h>
> +#include <linux/pinctrl/consumer.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm.h>
> +#include <linux/resource.h>
> +#include <linux/spinlock.h>
> +#include <linux/types.h>
> +#include <linux/version.h>
> +
> +/* Number of pins on BlueField */
> +#define MLXBF_GPIO_NR 54
> +
> +/* Pad Electrical Controls. */
> +#define GPIO_PAD_CONTROL__FIRST_WORD 0x0700 #define
> +GPIO_PAD_CONTROL_1__FIRST_WORD 0x0708 #define
> +GPIO_PAD_CONTROL_2__FIRST_WORD 0x0710 #define
> +GPIO_PAD_CONTROL_3__FIRST_WORD 0x0718
> +
> +#define GPIO_PIN_DIR_I 0x1040
> +#define GPIO_PIN_DIR_O 0x1048
> +#define GPIO_PIN_STATE 0x1000
> +#define GPIO_SCRATCHPAD 0x20
> +
> +#ifdef CONFIG_PM
> +struct bluefield_context_save_regs {
> + u64 gpio_scratchpad;
> + u64 gpio_pad_control[MLXBF_GPIO_NR];
> + u64 gpio_pin_dir_i;
> + u64 gpio_pin_dir_o;
> +};
> +#endif
> +
> +/* Device state structure. */
> +struct gpio_state {
> + struct list_head node;

Why do you need that? You're not using it anywhere AFAICT.

> + struct platform_device *pdev;

You're not using this either.

> +
> + struct gpio_chip gc;
> +
> + /* Must hold this lock to modify shared data. */
> + spinlock_t lock;
> +
> + /* Memory Address */
> + void __iomem *dc_base;
> +
> +#ifdef CONFIG_PM
> + struct bluefield_context_save_regs csave_regs; #endif };
> +
> +/* GPIO driver set input pins */
> +static int gpio_bf_set_input(struct gpio_chip *chip, unsigned int
> +offset) {
> + struct gpio_state *gs = gpiochip_get_data(chip);
> + u64 in;
> + u64 out;
> +
> + if (offset > MLXBF_GPIO_NR - 1) {
> + dev_err(chip->parent, "gpio input pins: Invalid offset %d\n",
> + offset);
> + return -EINVAL;
> + }

You don't need that, the subsystem makes sure this doesn't happen.
Same elsewhere.

> +
> + out = readq(gs->dc_base + GPIO_PIN_DIR_O);
> + in = readq(gs->dc_base + GPIO_PIN_DIR_I);
> +
> + writeq(out & ~BIT(offset), gs->dc_base + GPIO_PIN_DIR_O);
> + writeq(in | BIT(offset), gs->dc_base + GPIO_PIN_DIR_I);
> +

If you used the mmio regmap in this driver you could avoid both the locking (regmap uses a spinlock if fast_io is set to true) and manual bit updating here. You would do something like:
regmap_update_bits(map, gs->dc_base + GPIO_PIN_DIR_O, out & BIT(offset), ~BIT(offset)).

> + return 0;
> +}
> +
> +/* GPIO driver set output pins */
> +static int gpio_bf_set_output(struct gpio_chip *chip, unsigned int
> +offset) {
> + struct gpio_state *gs = gpiochip_get_data(chip);
> + u64 in;
> + u64 out;
> +
> + if (offset > MLXBF_GPIO_NR - 1) {
> + dev_err(chip->parent, "gpio output pins: Invalid offset %d\n",
> + offset);
> + return -EINVAL;
> + }
> +
> + out = readq(gs->dc_base + GPIO_PIN_DIR_O);
> + in = readq(gs->dc_base + GPIO_PIN_DIR_I);
> +
> + writeq(out | BIT(offset), gs->dc_base + GPIO_PIN_DIR_O);
> + writeq(in & ~BIT(offset), gs->dc_base + GPIO_PIN_DIR_I);
> +
> + return 0;
> +}
> +
> +/* GPIO driver output direction */
> +static int gpio_bf_set_output_lock(struct gpio_chip *chip,
> + unsigned int offset, int value) {
> + struct gpio_state *gs = gpiochip_get_data(chip);
> +
> + spin_lock(&gs->lock);
> + gpio_bf_set_output(chip, offset);
> + spin_unlock(&gs->lock);
> +
> + return 0;
> +}
> +
> +/* GPIO driver input direction */
> +static int gpio_bf_set_input_lock(struct gpio_chip *chip, unsigned
> +int offset) {
> + struct gpio_state *gs = gpiochip_get_data(chip);
> +
> + spin_lock(&gs->lock);
> + gpio_bf_set_input(chip, offset);
> + spin_unlock(&gs->lock);
> +
> + return 0;
> +}
> +
> +/* GPIO driver read routine. */
> +static int gpio_bf_get(struct gpio_chip *chip, unsigned int offset) {
> + u64 value;
> + struct gpio_state *gs = gpiochip_get_data(chip);
> +
> + value = readq(gs->dc_base + GPIO_PIN_STATE);
> +
> + return (value >> offset) & 1;
> +}
> +
> +/* GPIO driver write routine. */
> +static void gpio_bf_set(struct gpio_chip *chip, unsigned int offset,
> +int value) {
> + u64 data;
> + struct gpio_state *gs = gpiochip_get_data(chip);
> +
> + spin_lock(&gs->lock);
> + data = readq(gs->dc_base + GPIO_PIN_STATE);
> +
> + if (value)
> + data |= BIT(offset);
> + else
> + data &= ~BIT(offset);
> + writeq(data, gs->dc_base + GPIO_PIN_STATE);
> + spin_unlock(&gs->lock);
> +}
> +
> +/* GPIO driver initialization routine. */

These comments are obsolete to me. Everyone knows that probe, set, get, output and input functions do. It's clear from their names.

> +static int gpiodrv_probe(struct platform_device *pdev) {
> + struct gpio_state *gs;
> + struct device *dev = &pdev->dev;
> + struct gpio_chip *gc;
> + struct resource *dc_res;
> + int ret;
> +
> + dc_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + if (!dc_res)
> + return -EINVAL;
> +
> + if (devm_request_mem_region(&pdev->dev, dc_res->start,
> + resource_size(dc_res), "gpiodrv") == NULL)
> + return -EBUSY;
> +

Please use devm_ioremap_resource() here to save some code.

> + gs = devm_kzalloc(&pdev->dev, sizeof(struct gpio_state), GFP_KERNEL);
> + if (!gs)
> + return -ENOMEM;
> +
> + gs->dc_base = devm_ioremap(&pdev->dev, dc_res->start,
> + resource_size(dc_res));
> + if (!gs->dc_base)
> + return -ENOMEM;
> +
> + gc = &gs->gc;
> + gc->direction_input = gpio_bf_set_input_lock;
> + gc->get = gpio_bf_get;
> + gc->direction_output = gpio_bf_set_output_lock;
> + gc->set = gpio_bf_set;
> + gc->label = dev_name(dev);
> + gc->parent = &pdev->dev;
> + gc->owner = THIS_MODULE;
> + gc->base = 0;
> + gc->ngpio = MLXBF_GPIO_NR;
> +
> + ret = gpiochip_add_data(&gs->gc, gs);

Why not the resource managed version?

> + if (ret) {
> + dev_err(&pdev->dev, "Failed adding memory mapped gpiochip\n");
> + goto err;
> + }
> +
> + spin_lock_init(&gs->lock);
> + platform_set_drvdata(pdev, gs);
> + dev_info(&pdev->dev, "registered Mellanox BlueField GPIO");
> + return 0;
> +
> +err:
> + dev_err(&pdev->dev, "Probe, Failed\n");
> + return ret;
> +}
> +
> +#ifdef CONFIG_PM
> +/* GPIO driver suspend routine. */
> +static int gpiodrv_suspend(struct platform_device *pdev, pm_message_t
> +state) {
> + struct gpio_state *gs = platform_get_drvdata(pdev);
> +
> + gs->csave_regs.gpio_scratchpad = readq(gs->dc_base + GPIO_SCRATCHPAD);
> + gs->csave_regs.gpio_pad_control[0] =
> + readq(gs->dc_base + GPIO_PAD_CONTROL__FIRST_WORD);
> + gs->csave_regs.gpio_pad_control[1] =
> + readq(gs->dc_base + GPIO_PAD_CONTROL_1__FIRST_WORD);
> + gs->csave_regs.gpio_pad_control[2] =
> + readq(gs->dc_base + GPIO_PAD_CONTROL_2__FIRST_WORD);
> + gs->csave_regs.gpio_pad_control[3] =
> + readq(gs->dc_base + GPIO_PAD_CONTROL_3__FIRST_WORD);
> + gs->csave_regs.gpio_pin_dir_i = readq(gs->dc_base + GPIO_PIN_DIR_I);
> + gs->csave_regs.gpio_pin_dir_o = readq(gs->dc_base +
> + GPIO_PIN_DIR_O);
> +
> + return 0;
> +}
> +
> +/* GPIO driver resume routine. */
> +static int gpiodrv_resume(struct platform_device *pdev) {
> + struct gpio_state *gs = platform_get_drvdata(pdev);
> +
> + writeq(gs->csave_regs.gpio_scratchpad, gs->dc_base + GPIO_SCRATCHPAD);
> + writeq(gs->csave_regs.gpio_pad_control[0], gs->dc_base +
> + GPIO_PAD_CONTROL__FIRST_WORD);
> + writeq(gs->csave_regs.gpio_pad_control[1], gs->dc_base +
> + GPIO_PAD_CONTROL_1__FIRST_WORD);
> + writeq(gs->csave_regs.gpio_pad_control[2], gs->dc_base +
> + GPIO_PAD_CONTROL_2__FIRST_WORD);
> + writeq(gs->csave_regs.gpio_pad_control[3], gs->dc_base +
> + GPIO_PAD_CONTROL_3__FIRST_WORD);
> + writeq(gs->csave_regs.gpio_pin_dir_i, gs->dc_base + GPIO_PIN_DIR_I);
> + writeq(gs->csave_regs.gpio_pin_dir_o, gs->dc_base +
> + GPIO_PIN_DIR_O);
> +
> + return 0;
> +}
> +#endif
> +
> +/* GPIO driver exit routine. */
> +static int gpiodrv_remove(struct platform_device *pdev) {
> + struct gpio_state *gs = platform_get_drvdata(pdev);
> +
> + gpiochip_remove(&gs->gc);
> + iounmap(gs->dc_base);
> +
> + return 0;
> +}

The entire function is unnecessary - use devm_ where possible: both when mapping memory and adding the gpio chip.

> +
> +static const struct acpi_device_id gpiodrv_acpi_match[] = {
> + { "MLNXBF02", 0 },
> + {}
> +};
> +MODULE_DEVICE_TABLE(acpi, gpiodrv_acpi_match);
> +
> +static struct platform_driver gpiodrv_gpio_driver = {
> + .driver = {
> + .name = "gpiodrv",
> + .acpi_match_table = ACPI_PTR(gpiodrv_acpi_match),
> + },
> + .probe = gpiodrv_probe,
> + .remove = gpiodrv_remove,
> +#ifdef CONFIG_PM
> + .suspend = gpiodrv_suspend,
> + .resume = gpiodrv_resume,
> +#endif
> +};
> +
> +module_platform_driver(gpiodrv_gpio_driver);
> +
> +MODULE_DESCRIPTION("Mellanox BlueField GPIO Driver");
> +MODULE_AUTHOR("Mellanox Technologies"); MODULE_LICENSE("GPL");
> --
> 2.1.2
>

Best regards,
Bartosz Golaszewski

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