Date:	Fri, 11 May 2012 13:20:50 -0600
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] gpio: add MSIC gpio driver

On Tue, 24 Apr 2012 11:02:49 +0100, Alan Cox <alan@...rguk.ukuu.org.uk> wrote:
> From: Mathias Nyman <mathias.nyman@...ux.intel.com>
> 
> Add gpio support for Intel MSIC chips found in Intel Medfield platforms.
> MSIC supports totally 24 GPIOs with 16 low voltage and 8 high voltage pins.
> Driver uses MSIC mfd interface for MSIC access.
> 
> (Updated comment to indicate why locking is actually safe)
> 
> Signed-off-by: Mathias Nyman <mathias.nyman@...ux.intel.com>
> Signed-off-by: Alan Cox <alan@...ux.intel.com>

I've got a comment, but since this is a new driver I don't have any
problem applying it.  Any possible changes can be handled in a
follow-on patch, so I've merged it.

My main question is what is responsible for allocating the irq_descs
uses by this driver?  I don't see a call to irq_alloc_descs() in this
function.

Also, I'm pushing for gpio controllers that handle irqs to use an
irq_domain for mapping to a Linux irq.  It makes sense on the embedded
platforms, but I haven't looked enough at x86 to say if it should be
done there too (aside from when using DT).

g.

> ---
> 
>  drivers/gpio/Kconfig     |    8 +
>  drivers/gpio/Makefile    |    1 
>  drivers/gpio/gpio-msic.c |  339 ++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 348 insertions(+), 0 deletions(-)
>  create mode 100644 drivers/gpio/gpio-msic.c
> 
> 
> diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
> index 0833ed5..b686db8 100644
> --- a/drivers/gpio/Kconfig
> +++ b/drivers/gpio/Kconfig
> @@ -532,4 +532,12 @@ config GPIO_TPS65910
>  	help
>  	  Select this option to enable GPIO driver for the TPS65910
>  	  chip family.
> +
> +config GPIO_MSIC
> +	bool "Intel MSIC mixed signal gpio support"
> +	depends on MFD_INTEL_MSIC
> +	help
> +	  Enable support for GPIO on intel MSIC controllers found in
> +	  intel MID devices
> +
>  endif
> diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
> index ad963811..fe8d182 100644
> --- a/drivers/gpio/Makefile
> +++ b/drivers/gpio/Makefile
> @@ -34,6 +34,7 @@ obj-$(CONFIG_GPIO_MCP23S08)	+= gpio-mcp23s08.o
>  obj-$(CONFIG_GPIO_ML_IOH)	+= gpio-ml-ioh.o
>  obj-$(CONFIG_GPIO_MPC5200)	+= gpio-mpc5200.o
>  obj-$(CONFIG_GPIO_MPC8XXX)	+= gpio-mpc8xxx.o
> +obj-$(CONFIG_GPIO_MSIC)		+= gpio-msic.o
>  obj-$(CONFIG_GPIO_MSM_V1)	+= gpio-msm-v1.o
>  obj-$(CONFIG_GPIO_MSM_V2)	+= gpio-msm-v2.o
>  obj-$(CONFIG_GPIO_MXC)		+= gpio-mxc.o
> diff --git a/drivers/gpio/gpio-msic.c b/drivers/gpio/gpio-msic.c
> new file mode 100644
> index 0000000..71a838f
> --- /dev/null
> +++ b/drivers/gpio/gpio-msic.c
> @@ -0,0 +1,339 @@
> +/*
> + * Intel Medfield MSIC GPIO driver>
> + * Copyright (c) 2011, Intel Corporation.
> + *
> + * Author: Mathias Nyman <mathias.nyman@...ux.intel.com>
> + * Based on intel_pmic_gpio.c
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along with
> + * this program; if not, write to the Free Software Foundation, Inc.,
> + * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
> + *
> + */
> +
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/slab.h>
> +#include <linux/interrupt.h>
> +#include <linux/init.h>
> +#include <linux/gpio.h>
> +#include <linux/platform_device.h>
> +#include <linux/mfd/intel_msic.h>
> +
> +/* the offset for the mapping of global gpio pin to irq */
> +#define MSIC_GPIO_IRQ_OFFSET	0x100
> +
> +#define MSIC_GPIO_DIR_IN	0
> +#define MSIC_GPIO_DIR_OUT	BIT(5)
> +#define MSIC_GPIO_TRIG_FALL	BIT(1)
> +#define MSIC_GPIO_TRIG_RISE	BIT(2)
> +
> +/* masks for msic gpio output GPIOxxxxCTLO registers */
> +#define MSIC_GPIO_DIR_MASK	BIT(5)
> +#define MSIC_GPIO_DRV_MASK	BIT(4)
> +#define MSIC_GPIO_REN_MASK	BIT(3)
> +#define MSIC_GPIO_RVAL_MASK	(BIT(2) | BIT(1))
> +#define MSIC_GPIO_DOUT_MASK	BIT(0)
> +
> +/* masks for msic gpio input GPIOxxxxCTLI registers */
> +#define MSIC_GPIO_GLBYP_MASK	BIT(5)
> +#define MSIC_GPIO_DBNC_MASK	(BIT(4) | BIT(3))
> +#define MSIC_GPIO_INTCNT_MASK	(BIT(2) | BIT(1))
> +#define MSIC_GPIO_DIN_MASK	BIT(0)
> +
> +#define MSIC_NUM_GPIO		24
> +
> +struct msic_gpio {
> +	struct platform_device	*pdev;
> +	struct mutex		buslock;
> +	struct gpio_chip	chip;
> +	int			irq;
> +	unsigned		irq_base;
> +	unsigned long		trig_change_mask;
> +	unsigned		trig_type;
> +};
> +
> +/*
> + * MSIC has 24 gpios, 16 low voltage (1.2-1.8v) and 8 high voltage (3v).
> + * Both the high and low voltage gpios are divided in two banks.
> + * GPIOs are numbered with GPIO0LV0 as gpio_base in the following order:
> + * GPIO0LV0..GPIO0LV7: low voltage, bank 0, gpio_base
> + * GPIO1LV0..GPIO1LV7: low voltage, bank 1,  gpio_base + 8
> + * GPIO0HV0..GPIO0HV3: high voltage, bank 0, gpio_base + 16
> + * GPIO1HV0..GPIO1HV3: high voltage, bank 1, gpio_base + 20
> + */
> +
> +static int msic_gpio_to_ireg(unsigned offset)
> +{
> +	if (offset >= MSIC_NUM_GPIO)
> +		return -EINVAL;
> +
> +	if (offset < 8)
> +		return INTEL_MSIC_GPIO0LV0CTLI - offset;
> +	if (offset < 16)
> +		return INTEL_MSIC_GPIO1LV0CTLI - offset + 8;
> +	if (offset < 20)
> +		return INTEL_MSIC_GPIO0HV0CTLI - offset + 16;
> +
> +	return INTEL_MSIC_GPIO1HV0CTLI - offset + 20;
> +}
> +
> +static int msic_gpio_to_oreg(unsigned offset)
> +{
> +	if (offset >= MSIC_NUM_GPIO)
> +		return -EINVAL;
> +
> +	if (offset < 8)
> +		return INTEL_MSIC_GPIO0LV0CTLO - offset;
> +	if (offset < 16)
> +		return INTEL_MSIC_GPIO1LV0CTLO - offset + 8;
> +	if (offset < 20)
> +		return INTEL_MSIC_GPIO0HV0CTLO - offset + 16;
> +
> +	return INTEL_MSIC_GPIO1HV0CTLO + offset + 20;
> +}
> +
> +static int msic_gpio_direction_input(struct gpio_chip *chip, unsigned offset)
> +{
> +	int reg;
> +
> +	reg = msic_gpio_to_oreg(offset);
> +	if (reg < 0)
> +		return reg;
> +
> +	return intel_msic_reg_update(reg, MSIC_GPIO_DIR_IN, MSIC_GPIO_DIR_MASK);
> +}
> +
> +static int msic_gpio_direction_output(struct gpio_chip *chip,
> +			unsigned offset, int value)
> +{
> +	int reg;
> +	unsigned mask;
> +
> +	value = (!!value) | MSIC_GPIO_DIR_OUT;
> +	mask = MSIC_GPIO_DIR_MASK | MSIC_GPIO_DOUT_MASK;
> +
> +	reg = msic_gpio_to_oreg(offset);
> +	if (reg < 0)
> +		return reg;
> +
> +	return intel_msic_reg_update(reg, value, mask);
> +}
> +
> +static int msic_gpio_get(struct gpio_chip *chip, unsigned offset)
> +{
> +	u8 r;
> +	int ret;
> +	int reg;
> +
> +	reg = msic_gpio_to_ireg(offset);
> +	if (reg < 0)
> +		return reg;
> +
> +	ret = intel_msic_reg_read(reg, &r);
> +	if (ret < 0)
> +		return ret;
> +
> +	return r & MSIC_GPIO_DIN_MASK;
> +}
> +
> +static void msic_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
> +{
> +	int reg;
> +
> +	reg = msic_gpio_to_oreg(offset);
> +	if (reg < 0)
> +		return;
> +
> +	intel_msic_reg_update(reg, !!value , MSIC_GPIO_DOUT_MASK);
> +}
> +
> +/*
> + * This is called from genirq with mg->buslock locked and
> + * irq_desc->lock held. We can not access the scu bus here, so we
> + * store the change and update in the bus_sync_unlock() function below
> + */
> +static int msic_irq_type(struct irq_data *data, unsigned type)
> +{
> +	struct msic_gpio *mg = irq_data_get_irq_chip_data(data);
> +	u32 gpio = data->irq - mg->irq_base;
> +
> +	if (gpio >= mg->chip.ngpio)
> +		return -EINVAL;
> +
> +	/* mark for which gpio the trigger changed, protected by buslock */
> +	mg->trig_change_mask |= (1 << gpio);
> +	mg->trig_type = type;
> +
> +	return 0;
> +}
> +
> +static int msic_gpio_to_irq(struct gpio_chip *chip, unsigned offset)
> +{
> +	struct msic_gpio *mg = container_of(chip, struct msic_gpio, chip);
> +	return mg->irq_base + offset;
> +}
> +
> +static void msic_bus_lock(struct irq_data *data)
> +{
> +	struct msic_gpio *mg = irq_data_get_irq_chip_data(data);
> +	mutex_lock(&mg->buslock);
> +}
> +
> +static void msic_bus_sync_unlock(struct irq_data *data)
> +{
> +	struct msic_gpio *mg = irq_data_get_irq_chip_data(data);
> +	int offset;
> +	int reg;
> +	u8 trig = 0;
> +
> +	/* We can only get one change at a time as the buslock covers the
> +	   entire transaction. The irq_desc->lock is dropped before we are
> +	   called but that is fine */
> +	if (mg->trig_change_mask) {
> +		offset = __ffs(mg->trig_change_mask);
> +
> +		reg = msic_gpio_to_ireg(offset);
> +		if (reg < 0)
> +			goto out;
> +
> +		if (mg->trig_type & IRQ_TYPE_EDGE_RISING)
> +			trig |= MSIC_GPIO_TRIG_RISE;
> +		if (mg->trig_type & IRQ_TYPE_EDGE_FALLING)
> +			trig |= MSIC_GPIO_TRIG_FALL;
> +
> +		intel_msic_reg_update(reg, trig, MSIC_GPIO_INTCNT_MASK);
> +		mg->trig_change_mask = 0;
> +	}
> +out:
> +	mutex_unlock(&mg->buslock);
> +}
> +
> +/* Firmware does all the masking and unmasking for us, no masking here. */
> +static void msic_irq_unmask(struct irq_data *data) { }
> +
> +static void msic_irq_mask(struct irq_data *data) { }
> +
> +static struct irq_chip msic_irqchip = {
> +	.name			= "MSIC-GPIO",
> +	.irq_mask		= msic_irq_mask,
> +	.irq_unmask		= msic_irq_unmask,
> +	.irq_set_type		= msic_irq_type,
> +	.irq_bus_lock		= msic_bus_lock,
> +	.irq_bus_sync_unlock	= msic_bus_sync_unlock,
> +};
> +
> +static void msic_gpio_irq_handler(unsigned irq, struct irq_desc *desc)
> +{
> +	struct irq_data *data = irq_desc_get_irq_data(desc);
> +	struct msic_gpio *mg = irq_data_get_irq_handler_data(data);
> +	struct irq_chip *chip = irq_data_get_irq_chip(data);
> +	struct intel_msic *msic = pdev_to_intel_msic(mg->pdev);
> +	int i;
> +	int bitnr;
> +	u8 pin;
> +	unsigned long pending = 0;
> +
> +	for (i = 0; i < (mg->chip.ngpio / BITS_PER_BYTE); i++) {
> +		intel_msic_irq_read(msic, INTEL_MSIC_GPIO0LVIRQ + i, &pin);
> +		pending = pin;
> +
> +		if (pending) {
> +			for_each_set_bit(bitnr, &pending, BITS_PER_BYTE)
> +				generic_handle_irq(mg->irq_base +
> +						   (i * BITS_PER_BYTE) + bitnr);
> +		}
> +	}
> +	chip->irq_eoi(data);
> +}
> +
> +static int __devinit platform_msic_gpio_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct intel_msic_gpio_pdata *pdata = dev->platform_data;
> +	struct msic_gpio *mg;
> +	int irq = platform_get_irq(pdev, 0);
> +	int retval;
> +	int i;
> +
> +	if (irq < 0) {
> +		dev_err(dev, "no IRQ line\n");
> +		return -EINVAL;
> +	}
> +
> +	if (!pdata || !pdata->gpio_base) {
> +		dev_err(dev, "incorrect or missing platform data\n");
> +		return -EINVAL;
> +	}
> +
> +	mg = kzalloc(sizeof(*mg), GFP_KERNEL);
> +	if (!mg)
> +		return -ENOMEM;
> +
> +	dev_set_drvdata(dev, mg);
> +
> +	mg->pdev = pdev;
> +	mg->irq = irq;
> +	mg->irq_base = pdata->gpio_base + MSIC_GPIO_IRQ_OFFSET;
> +	mg->chip.label = "msic_gpio";
> +	mg->chip.direction_input = msic_gpio_direction_input;
> +	mg->chip.direction_output = msic_gpio_direction_output;
> +	mg->chip.get = msic_gpio_get;
> +	mg->chip.set = msic_gpio_set;
> +	mg->chip.to_irq = msic_gpio_to_irq;
> +	mg->chip.base = pdata->gpio_base;
> +	mg->chip.ngpio = MSIC_NUM_GPIO;
> +	mg->chip.can_sleep = 1;
> +	mg->chip.dev = dev;
> +
> +	mutex_init(&mg->buslock);
> +
> +	retval = gpiochip_add(&mg->chip);
> +	if (retval) {
> +		dev_err(dev, "Adding MSIC gpio chip failed\n");
> +		goto err;
> +	}
> +
> +	for (i = 0; i < mg->chip.ngpio; i++) {
> +		irq_set_chip_data(i + mg->irq_base, mg);
> +		irq_set_chip_and_handler_name(i + mg->irq_base,
> +					      &msic_irqchip,
> +					      handle_simple_irq,
> +					      "demux");
> +	}
> +	irq_set_chained_handler(mg->irq, msic_gpio_irq_handler);
> +	irq_set_handler_data(mg->irq, mg);
> +
> +	return 0;
> +err:
> +	kfree(mg);
> +	return retval;
> +}
> +
> +static struct platform_driver platform_msic_gpio_driver = {
> +	.driver = {
> +		.name		= "msic_gpio",
> +		.owner		= THIS_MODULE,
> +	},
> +	.probe		= platform_msic_gpio_probe,
> +};
> +
> +static int __init platform_msic_gpio_init(void)
> +{
> +	return platform_driver_register(&platform_msic_gpio_driver);
> +}
> +
> +subsys_initcall(platform_msic_gpio_init);
> +
> +MODULE_AUTHOR("Mathias Nyman <mathias.nyman@...ux.intel.com>");
> +MODULE_DESCRIPTION("Intel Medfield MSIC GPIO driver");
> +MODULE_LICENSE("GPL v2");
> 

-- 
Grant Likely, B.Sc, P.Eng.
Secret Lab Technologies, Ltd.
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