mfd: atmel-flexcom: Add a driver for Atmel Flexible Serial Communication Unit

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@atmel.com>
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

3 files changed, 116 insertions, 0 deletions

diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 99d63675f073..87e84e7c71da 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 d6c21e3c409f..a8b76b81b467 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -164,6 +164,7 @@ 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-$(CONFIG_MFD_INTEL_LPSS)    += intel-lpss.o
 obj-$(CONFIG_MFD_INTEL_LPSS_PCI)        += intel-lpss-pci.o
diff --git a/drivers/mfd/atmel-flexcom.c b/drivers/mfd/atmel-flexcom.c
new file mode 100644
index 000000000000..e8e67be6b493
--- /dev/null
+++ b/drivers/mfd/atmel-flexcom.c
@@ -0,0 +1,104 @@
+/*
+ * Driver for Atmel Flexcom
+ *
+ * Copyright (C) 2015 Atmel Corporation
+ *
+ * Author: Cyrille Pitchen <cyrille.pitchen@atmel.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.
+ *
+ * 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>
+#include <dt-bindings/mfd/atmel-flexcom.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_OFFSET   (0)  /* Operating Mode */
+#define FLEX_MR_OPMODE_MASK     (0x3 << FLEX_MR_OPMODE_OFFSET)
+#define FLEX_MR_OPMODE(opmode)  (((opmode) << FLEX_MR_OPMODE_OFFSET) &  \
+                                 FLEX_MR_OPMODE_MASK)
+
+
+static int atmel_flexcom_probe(struct platform_device *pdev)
+{
+        struct device_node *np = pdev->dev.of_node;
+        struct clk *clk;
+        struct resource *res;
+        void __iomem *base;
+        u32 opmode;
+        int err;
+
+        err = of_property_read_u32(np, "atmel,flexcom-mode", &opmode);
+        if (err)
+                return err;
+
+        if (opmode < ATMEL_FLEXCOM_MODE_USART ||
+            opmode > ATMEL_FLEXCOM_MODE_TWI)
+                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(FLEX_MR_OPMODE(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 <cyrille.pitchen@atmel.com>");
+MODULE_DESCRIPTION("Atmel Flexcom MFD driver");
+MODULE_LICENSE("GPL v2");