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Message-ID: <20150615193257.42c9df3d@bbrezillon>
Date: Mon, 15 Jun 2015 19:32:57 +0200
From: Boris Brezillon <boris.brezillon@...e-electrons.com>
To: Cyrille Pitchen <cyrille.pitchen@...el.com>
Cc: <nicolas.ferre@...el.com>, <alexandre.belloni@...e-electrons.com>,
<sameo@...ux.intel.com>, <lee.jones@...aro.org>,
<linux-arm-kernel@...ts.infradead.org>,
<linux-kernel@...r.kernel.org>, <robh+dt@...nel.org>,
<pawel.moll@....com>, <mark.rutland@....com>,
<ijc+devicetree@...lion.org.uk>, <galak@...eaurora.org>,
<devicetree@...r.kernel.org>
Subject: Re: [PATCH linux-next 2/2] mfd: flexcom: add a driver for Atmel
Flexible Serial Communication Unit
On Mon, 15 Jun 2015 18:38:05 +0200
Cyrille Pitchen <cyrille.pitchen@...el.com> 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, according to the value of the new
> "atmel,flexcom-mode" device tree property.
>
> 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 <cyrille.pitchen@...el.com>
> ---
> drivers/mfd/Kconfig | 11 +++++
> drivers/mfd/Makefile | 1 +
> drivers/mfd/atmel-flexcom.c | 97 +++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 109 insertions(+)
> create mode 100644 drivers/mfd/atmel-flexcom.c
>
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index aefbbbf..4aebf08 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.
> +
> 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 ea40e07..0705eb2 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 0000000..14c35e6
> --- /dev/null
> +++ b/drivers/mfd/atmel-flexcom.c
> @@ -0,0 +1,97 @@
> +/*
> + * Driver for Atmel Flexcom
> + *
> + * Copyright (C) 2015 Atmel Corporation
> + *
> + * Author: Cyrille Pitchen <cyrille.pitchen@...el.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + */
> +
> +#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>
> +
> +#define FX_MR 0x0
> +#define FX_RHR 0x10
> +#define FX_THR 0x20
> +#define FX_VERSION 0xfc
> +
> +#define FX_MR_NO_COM 0
> +#define FX_MR_USART 1
> +#define FX_MR_SPI 2
> +#define FX_MR_TWI 3
> +
> +
> +static int atmel_flexcom_probe(struct platform_device *pdev)
> +{
> + struct clk *clk;
> + struct resource *res;
> + unsigned char __iomem *map;
> + unsigned int version, mr;
> + const char *mode;
> + int err;
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + map = devm_ioremap_resource(&pdev->dev, res);
If you take the approach I suggested in the DT binding review,
you shouldn't reserve the whole memory region, just the flexcom
part(0x0 to 0x200).
> + if (IS_ERR(map))
> + return PTR_ERR(map);
> +
> + clk = devm_clk_get(&pdev->dev, NULL);
> + if (IS_ERR(clk))
> + return PTR_ERR(clk);
> +
> + err = of_property_read_string(pdev->dev.of_node,
> + "atmel,flexcom-mode", &mode);
> + if (err)
> + return err;
> +
> + if (!strcmp(mode, "usart"))
> + mr = FX_MR_USART;
> + else if (!strcmp(mode, "spi"))
> + mr = FX_MR_SPI;
> + else if (!strcmp(mode, "twi") || !strcmp(mode, "i2c"))
> + mr = FX_MR_TWI;
> + else
> + return -EINVAL;
> +
> + clk_prepare_enable(clk);
> + version = __raw_readl(map + FX_VERSION);
> + __raw_writel(mr, map + FX_MR);
> + clk_disable_unprepare(clk);
Is there a good reason to use the __raw versions of the writel/readl
functions ?
--
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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