Subject: [PATCH v7 2/2] mfd: atmel-flexcom: add a driver for Atmel Flexible Serial Communication Unit

From: [email-masked] (Nicolas Ferre)
Date: Fri, 24 Jul 2015 10:47:03 +0200

Le 24/07/2015 10:43, Lee Jones a ?crit :
> On Thu, 23 Jul 2015, Cyrille Pitchen wrote:
> 
>> This driver supports the new Atmel Flexcom. The Flexcom is a wrapper which
>> integrates one SPI controller, one I2C controller and one USART. Only one
>> function can be enabled at a time. This driver selects the function once
>> for all, when the Flexcom is probed, using the "reg" property of the first
>> (should be unique) available DT child node.
>>
>> This driver has chosen to present the Flexcom to the system as a MFD so
>> the implementation is seamless for the existing Atmel SPI, I2C and USART
>> drivers.
>>
>> Also the Flexcom embeds FIFOs: the latest patches of the SPI, I2C and
>> USART drivers take advantage of this new feature.
>>
>> Signed-off-by: Cyrille Pitchen <[email-masked]>
>> ---
>>  drivers/mfd/Kconfig         |  11 +++++
>>  drivers/mfd/Makefile        |   1 +
>>  drivers/mfd/atmel-flexcom.c | 113 ++++++++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 125 insertions(+)
>>  create mode 100644 drivers/mfd/atmel-flexcom.c
>>
>> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
>> index 653815950aa2..2c75472c679c 100644
>> --- a/drivers/mfd/Kconfig
>> +++ b/drivers/mfd/Kconfig
>> @@ -60,6 +60,17 @@ config MFD_AAT2870_CORE
>>  	  additional drivers must be enabled in order to use the
>>  	  functionality of the device.
>>  
>> +config MFD_ATMEL_FLEXCOM
>> +	tristate "Atmel Flexcom (Flexible Serial Communication Unit)"
>> +	select MFD_CORE
>> +	depends on OF
>> +	help
>> +	  Select this to get support for Atmel Flexcom. This is a wrapper
>> +	  which embeds a SPI controller, a I2C controller and a USART. Only
>> +	  one function can be used at a time. The choice is done at boot time
>> +	  by the probe function of this MFD driver according to a device tree
>> +	  property.
> 
> Please grep for QCOM_GSBI in drivers/soc/qcom/*
> 
> Similar right?
> 
> Perhaps this should live in drivers/soc/atmel/* instead?
> 
>>  config MFD_ATMEL_HLCDC
>>  	tristate "Atmel HLCDC (High-end LCD Controller)"
>>  	select MFD_CORE
>> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
>> index ea40e076cb61..0705eb2d873d 100644
>> --- a/drivers/mfd/Makefile
>> +++ b/drivers/mfd/Makefile
>> @@ -160,6 +160,7 @@ obj-$(CONFIG_MFD_SPMI_PMIC)	+= qcom-spmi-pmic.o
>>  obj-$(CONFIG_TPS65911_COMPARATOR)	+= tps65911-comparator.o
>>  obj-$(CONFIG_MFD_TPS65090)	+= tps65090.o
>>  obj-$(CONFIG_MFD_AAT2870_CORE)	+= aat2870-core.o
>> +obj-$(CONFIG_MFD_ATMEL_FLEXCOM)	+= atmel-flexcom.o
>>  obj-$(CONFIG_MFD_ATMEL_HLCDC)	+= atmel-hlcdc.o
>>  obj-$(CONFIG_MFD_INTEL_MSIC)	+= intel_msic.o
>>  obj-$(CONFIG_MFD_PALMAS)	+= palmas.o
>> diff --git a/drivers/mfd/atmel-flexcom.c b/drivers/mfd/atmel-flexcom.c
>> new file mode 100644
>> index 000000000000..0d06b70696b0
>> --- /dev/null
>> +++ b/drivers/mfd/atmel-flexcom.c
>> @@ -0,0 +1,113 @@
>> +/*
>> + * Driver for Atmel Flexcom
>> + *
>> + * Copyright (C) 2015 Atmel Corporation
>> + *
>> + * Author: Cyrille Pitchen <[email-masked]>
>> + *
>> + * 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.
>> + *
>> + * This program is distributed in the hope that 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, see <http://www.gnu.org/licenses/>.
>> + */
>> +
>> +#include <linux/module.h>
>> +#include <linux/types.h>
>> +#include <linux/kernel.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/of.h>
>> +#include <linux/of_platform.h>
>> +#include <linux/err.h>
>> +#include <linux/io.h>
>> +#include <linux/clk.h>
>> +
>> +/* I/O register offsets */
>> +#define FLEX_MR		0x0	/* Mode Register */
>> +#define FLEX_VERSION	0xfc	/* Version Register */
>> +
>> +/* Mode Register bit fields */
>> +#define FLEX_MR_OPMODE_MASK	0x3
>> +#define FLEX_MR_OPMODE_NO_COM	0x0
>> +#define FLEX_MR_OPMODE_USART	0x1
>> +#define FLEX_MR_OPMODE_SPI	0x2
>> +#define FLEX_MR_OPMODE_TWI	0x3
>> +
>> +
>> +static int atmel_flexcom_probe(struct platform_device *pdev)
>> +{
>> +	struct device_node *child, *np = pdev->dev.of_node;
>> +	struct clk *clk;
>> +	struct resource *res;
>> +	void __iomem *base;
>> +	u32 opmode;
>> +	int err;
>> +
>> +	child = of_get_next_available_child(np, NULL);
>> +	if (!child)
>> +		return -ENODEV;
>> +
>> +	/*
>> +	 * The Operating Mode is stored into the first u32 of the reg property
>> +	 * of the child.
>> +	 */
>> +	err = of_property_read_u32_index(child, "reg", 0, &opmode);
>> +	of_node_put(child);
> 
> Don't think you need to of_node_put() after a u32 read.

Well, it's after an of_get_next_available_child() which is similar to
of_get_next_child(). It is said to release the node by calling
of_node_put()... So I suspect it's necessary.

Bye,

> 
>> +	if (err)
>> +		return -EINVAL;
> 
> Why are you making up your own return value.
> 
> Just return err.
> 
>> +	if ((opmode == FLEX_MR_OPMODE_NO_COM) ||
>> +	    (opmode & ~FLEX_MR_OPMODE_MASK))
>> +		return -EINVAL;
>> +
>> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> +	base = devm_ioremap_resource(&pdev->dev, res);
>> +	if (IS_ERR(base))
>> +		return PTR_ERR(base);
>> +
>> +	clk = devm_clk_get(&pdev->dev, NULL);
>> +	if (IS_ERR(clk))
>> +		return PTR_ERR(clk);
>> +
>> +	err = clk_prepare_enable(clk);
>> +	if (err)
>> +		return err;
>> +
>> +	/*
>> +	 * Set the Operating Mode in the Mode Register: only the selected device
>> +	 * is clocked. Hence, registers of the other serial devices remain
>> +	 * inaccessible and are read as zero. Also the external I/O lines of the
>> +	 * Flexcom are muxed to reach the selected device.
>> +	 */
>> +	writel(opmode, base + FLEX_MR);
>> +
>> +	clk_disable_unprepare(clk);
>> +
>> +	return of_platform_populate(np, NULL, NULL, &pdev->dev);
>> +}
>> +
>> +static const struct of_device_id atmel_flexcom_of_match[] = {
>> +	{ .compatible = "atmel,sama5d2-flexcom" },
>> +	{ /* sentinel */ }
>> +};
>> +MODULE_DEVICE_TABLE(of, atmel_flexcom_of_match);
>> +
>> +static struct platform_driver atmel_flexcom_driver = {
>> +	.probe	= atmel_flexcom_probe,
>> +	.driver	= {
>> +		.name		= "atmel_flexcom",
>> +		.of_match_table	= atmel_flexcom_of_match,
>> +	},
>> +};
>> +
>> +module_platform_driver(atmel_flexcom_driver);
>> +
>> +MODULE_AUTHOR("Cyrille Pitchen <[email-masked]>");
>> +MODULE_DESCRIPTION("Atmel Flexcom MFD driver");
>> +MODULE_LICENSE("GPL v2");
> 

-- 
Nicolas Ferre