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Date: Tue, 19 Jan 2016 12:09:08 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Sudip Mukherjee <sudipm.mukherjee@...il.com>,
Peter Hung <hpeter@...il.com>
Cc: Linus Walleij <linus.walleij@...aro.org>,
Alexandre Courbot <gnurou@...il.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jiri Slaby <jslaby@...e.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
Rob Groner <rgroner@....com>
Subject: Re: [PATCH v5] serial: 8250: add gpio support to exar
On Tue, Jan 19, 2016 at 8:06 AM, Sudip Mukherjee
<sudipm.mukherjee@...il.com> wrote:
> Exar XR17V352/354/358 chips have 16 multi-purpose inputs/outputs which
> can be controlled using gpio interface.
> Add support to use these pins.
+ Peter Hung.
Seems Fintek HW is going similar way you, guys, have to decide how to
proceed in general. I like this way Sudip made here, though I still
few comments below.
First of all, can we split it to two patches like cooking GPIO driver
first, then extend Exar piece of serial driver?
I also would like to vote for splitting out first Exar parts from
8250_pci like Peter did for Fintek.
> +++ b/drivers/gpio/gpio-exar.c
> @@ -0,0 +1,255 @@
> +/*
> + * GPIO driver for Exar XR17V35X chip
> + *
> + * Copyright (C) 2015 Sudip Mukherjee <sudipm.mukherjee@...il.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +#include <linux/platform_device.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/device.h>
> +#include <linux/pci.h>
> +#include <linux/gpio.h>
> +
> +#define EXAR_OFFSET_MPIOLVL_LO 0x90
> +#define EXAR_OFFSET_MPIOSEL_LO 0x93
> +#define EXAR_OFFSET_MPIOLVL_HI 0x96
> +#define EXAR_OFFSET_MPIOSEL_HI 0x99
> +
> +static LIST_HEAD(exar_list);
> +static DEFINE_MUTEX(exar_mtx); /* lock while manipulating the list */
I don't think it's a useful comment, though you may rename
exar_mtx to exar_list_mutex. It will be enough I guess.
> +
> +struct exar_gpio_chip {
> + struct gpio_chip gpio_chip;
> + struct mutex lock;
> + struct list_head list;
> + int index;
> + void __iomem *regs;
> + char name[16];
> +};
> +
> +#define to_exar_chip(n) container_of(n, struct exar_gpio_chip, gpio_chip)
> +
> +static inline unsigned int read_exar_reg(struct exar_gpio_chip *chip,
> + int offset)
> +{
> + pr_debug("%s regs=%p offset=%x\n", __func__, chip->regs, offset);
dev_dbg()
> + return readb(chip->regs + offset);
> +}
> +
> +static inline void write_exar_reg(struct exar_gpio_chip *chip, int offset,
> + int value)
> +{
> + pr_debug("%s regs=%p value=%x offset=%x\n", __func__, chip->regs,
> + value, offset);
Ditto.
> +static void exar_set(struct gpio_chip *chip, unsigned int reg, int val,
> + unsigned int offset)
This one by implementation looks like exar_update()
> +{
> + struct exar_gpio_chip *exar_gpio = to_exar_chip(chip);
> + int temp;
Looks like value -> val, maybe temp -> tmp?
It's minor, up to you.
> +static int exar_direction_output(struct gpio_chip *chip, unsigned int offset,
> + int value)
> +{
> + if (offset < 8)
> + exar_set(chip, EXAR_OFFSET_MPIOSEL_LO, 0, offset);
> + else
> + exar_set(chip, EXAR_OFFSET_MPIOSEL_HI, 0, offset - 8);
> + return 0;
> +}
> +
> +static int exar_direction_input(struct gpio_chip *chip, unsigned int offset)
> +{
> + if (offset < 8)
> + exar_set(chip, EXAR_OFFSET_MPIOSEL_LO, 1, offset);
> + else
> + exar_set(chip, EXAR_OFFSET_MPIOSEL_HI, 1, offset - 8);
> + return 0;
> +}
Maybe
static int exar_set_direction(struct gpio_chip *chip, int direction,
unsigned int offset)
{
if (offset < 8)
exar_set(chip, EXAR_OFFSET_MPIOSEL_LO, direction, offset - 0);
else
exar_set(chip, EXAR_OFFSET_MPIOSEL_HI, direction, offset - 8);
return 0;
}
static int exar_direction_output(struct gpio_chip *chip, unsigned int offset)
{
return exar_set_direction(chip, 0, offset);
}
static int exar_direction_input(struct gpio_chip *chip, unsigned int offset)
{
return exar_set_direction(chip, 1, offset);
}
?
> +
> +static int exar_get(struct gpio_chip *chip, unsigned int reg)
> +{
> + int value;
> + struct exar_gpio_chip *exar_gpio = to_exar_chip(chip);
struct exar_gpio_chip *exar_gpio = to_exar_chip(chip);
int value;
> + if (!exar_gpio) {
> + pr_err("%s exar_gpio is NULL\n", __func__);
I don't think this is useful message and even entire condition. How is
it possible that you get it NULL?
> + return -ENOMEM;
> + }
> +
> + mutex_lock(&exar_gpio->lock);
> + value = read_exar_reg(exar_gpio, reg);
> + mutex_unlock(&exar_gpio->lock);
> +
> + return value;
> +}
> +
> +static int exar_get_direction(struct gpio_chip *chip, unsigned int offset)
> +{
> + int val;
> +
> + if (offset < 8) {
> + val = exar_get(chip, EXAR_OFFSET_MPIOSEL_LO);
val = exar_get(chip, EXAR_OFFSET_MPIOSEL_LO) >> offset;
> + } else {
> + val = exar_get(chip, EXAR_OFFSET_MPIOSEL_HI);
val = exar_get(chip, EXAR_OFFSET_MPIOSEL_HI) >> (offset - 8);
> + offset -= 8;
> + }
> +
> + if (val > 0) {
> + val >>= offset;
> + val &= 0x01;
> + }
> +
> + return val;
return val & 0x01;
(Assume you have no error values returned)
> +}
> +
> +static int exar_get_value(struct gpio_chip *chip, unsigned int offset)
> +{
> + int val;
> +
> + if (offset < 8) {
> + val = exar_get(chip, EXAR_OFFSET_MPIOLVL_LO);
> + } else {
> + val = exar_get(chip, EXAR_OFFSET_MPIOLVL_HI);
> + offset -= 8;
> + }
> + val >>= offset;
> + val &= 0x01;
Ditto
> +
> + return val;
> +}
> +
> +static void exar_set_value(struct gpio_chip *chip, unsigned int offset,
> + int value)
> +{
> + if (offset < 8)
> + exar_set(chip, EXAR_OFFSET_MPIOLVL_LO, value, offset);
> + else
> + exar_set(chip, EXAR_OFFSET_MPIOLVL_HI, value, offset - 8);
> +}
> +
> +static int gpio_exar_probe(struct platform_device *pdev)
> +{
> + struct pci_dev *dev = platform_get_drvdata(pdev);
> + struct exar_gpio_chip *exar_gpio, *exar_temp;
> + void __iomem *p;
> + int index = 1;
> + int ret;
> +
> + if (dev->vendor != PCI_VENDOR_ID_EXAR)
> + return -ENODEV;
> +
> + p = pci_ioremap_bar(dev, 0);
So, if it would be separate driver for 8250_exar.c (by the way what is
8250_exar_st16c554.c?) you will use managed functions here…
> + if (!p)
> + return -ENOMEM;
> +
> + exar_gpio = devm_kzalloc(&dev->dev, sizeof(*exar_gpio), GFP_KERNEL);
> + if (!exar_gpio) {
> + ret = -ENOMEM;
> + goto err_unmap;
…and thus no need to free resources explicitly.
> + }
> +
> + mutex_init(&exar_gpio->lock);
> + INIT_LIST_HEAD(&exar_gpio->list);
> +
> + mutex_lock(&exar_mtx);
> + /* find the first unused index */
> + list_for_each_entry(exar_temp, &exar_list, list) {
> + if (exar_temp->index == index) {
> + index++;
Shouldn't be ida/idr value?
> + continue;
> + }
> + }
> +
> + sprintf(exar_gpio->name, "exar_gpio%d", index);
> + exar_gpio->gpio_chip.label = exar_gpio->name;
> + exar_gpio->gpio_chip.parent = &dev->dev;
> + exar_gpio->gpio_chip.direction_output = exar_direction_output;
> + exar_gpio->gpio_chip.direction_input = exar_direction_input;
> + exar_gpio->gpio_chip.get_direction = exar_get_direction;
> + exar_gpio->gpio_chip.get = exar_get_value;
> + exar_gpio->gpio_chip.set = exar_set_value;
> + exar_gpio->gpio_chip.base = -1;
> + exar_gpio->gpio_chip.ngpio = 16;
> + exar_gpio->gpio_chip.owner = THIS_MODULE;
Does core set it for you?
> + exar_gpio->regs = p;
> + exar_gpio->index = index;
> +
> + ret = gpiochip_add(&exar_gpio->gpio_chip);
> + if (ret)
> + goto err_destroy;
> +
> + list_add_tail(&exar_gpio->list, &exar_list);
> + mutex_unlock(&exar_mtx);
> +
> + platform_set_drvdata(pdev, exar_gpio);
> +
> + return 0;
> +
> +err_destroy:
> + mutex_unlock(&exar_mtx);
> + mutex_destroy(&exar_gpio->lock);
I think it would be done in other way if you use IDR framework.
> +err_unmap:
> + iounmap(p);
> + return ret;
> +}
> +
> +static int gpio_exar_remove(struct platform_device *pdev)
> +{
> + struct exar_gpio_chip *exar_gpio, *exar_temp1, *exar_temp2;
> +
> + exar_gpio = platform_get_drvdata(pdev);
> +
> + mutex_lock(&exar_mtx);
> + list_for_each_entry_safe(exar_temp1, exar_temp2, &exar_list, list) {
> + if (exar_temp1->index == exar_gpio->index) {
> + list_del(&exar_temp1->list);
> + break;
Ditto.
> + }
> + }
> + mutex_unlock(&exar_mtx);
> +
> + gpiochip_remove(&exar_gpio->gpio_chip);
> + mutex_destroy(&exar_gpio->lock);
> + iounmap(exar_gpio->regs);
> +
> + return 0;
> +}
> +
> +static struct platform_driver gpio_exar_driver = {
> + .probe = gpio_exar_probe,
> + .remove = gpio_exar_remove,
> + .driver = {
> + .name = "gpio_exar",
DRIVER_NAME
> + },
> +};
> +
> +static const struct platform_device_id gpio_exar_id[] = {
> + { "gpio_exar", 0},
This is default fallback. I don't think you need this at all (example
in my mind is dw_dmac driver, where you can't find such line). But
please recheck.
> + { },
> +};
> +
> +MODULE_DEVICE_TABLE(platform, gpio_exar_id);
> +
> +module_platform_driver(gpio_exar_driver)
> +
> +MODULE_DESCRIPTION("Exar GPIO driver");
> +MODULE_AUTHOR("Sudip Mukherjee <sudipm.mukherjee@...il.com>");
> +MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:" DRIVER_NAME);
where DRIVER_NAME is defined somewhere on top.
--
With Best Regards,
Andy Shevchenko
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