drivers/mfd/atmel-flexcom.c

   1 /*
   2  * Driver for Atmel Flexcom
   3  *
   4  * Copyright (C) 2015 Atmel Corporation
   5  *
   6  * Author: Cyrille Pitchen <cyrille.pitchen@atmel.com>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  *
  12  * This program is distributed in the hope that it will be useful, but WITHOUT
  13  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  15  * more details.
  16  *
  17  * You should have received a copy of the GNU General Public License along with
  18  * this program.  If not, see <http://www.gnu.org/licenses/>.
  19  */
  20
  21 #include <linux/module.h>
  22 #include <linux/types.h>
  23 #include <linux/kernel.h>
  24 #include <linux/platform_device.h>
  25 #include <linux/of.h>
  26 #include <linux/of_platform.h>
  27 #include <linux/err.h>
  28 #include <linux/io.h>
  29 #include <linux/clk.h>
  30 #include <dt-bindings/mfd/atmel-flexcom.h>
  31
  32 /* I/O register offsets */
  33 #define FLEX_MR         0x0     /* Mode Register */
  34 #define FLEX_VERSION    0xfc    /* Version Register */
  35
  36 /* Mode Register bit fields */
  37 #define FLEX_MR_OPMODE_OFFSET   (0)  /* Operating Mode */
  38 #define FLEX_MR_OPMODE_MASK     (0x3 << FLEX_MR_OPMODE_OFFSET)
  39 #define FLEX_MR_OPMODE(opmode)  (((opmode) << FLEX_MR_OPMODE_OFFSET) &  \
  40                                  FLEX_MR_OPMODE_MASK)
  41
  42
  43 static int atmel_flexcom_probe(struct platform_device *pdev)
  44 {
  45         struct device_node *np = pdev->dev.of_node;
  46         struct clk *clk;
  47         struct resource *res;
  48         void __iomem *base;
  49         u32 opmode;
  50         int err;
  51
  52         err = of_property_read_u32(np, "atmel,flexcom-mode", &opmode);
  53         if (err)
  54                 return err;
  55
  56         if (opmode < ATMEL_FLEXCOM_MODE_USART ||
  57             opmode > ATMEL_FLEXCOM_MODE_TWI)
  58                 return -EINVAL;
  59
  60         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  61         base = devm_ioremap_resource(&pdev->dev, res);
  62         if (IS_ERR(base))
  63                 return PTR_ERR(base);
  64
  65         clk = devm_clk_get(&pdev->dev, NULL);
  66         if (IS_ERR(clk))
  67                 return PTR_ERR(clk);
  68
  69         err = clk_prepare_enable(clk);
  70         if (err)
  71                 return err;
  72
  73         /*
  74          * Set the Operating Mode in the Mode Register: only the selected device
  75          * is clocked. Hence, registers of the other serial devices remain
  76          * inaccessible and are read as zero. Also the external I/O lines of the
  77          * Flexcom are muxed to reach the selected device.
  78          */
  79         writel(FLEX_MR_OPMODE(opmode), base + FLEX_MR);
  80
  81         clk_disable_unprepare(clk);
  82
  83         return of_platform_populate(np, NULL, NULL, &pdev->dev);
  84 }
  85
  86 static const struct of_device_id atmel_flexcom_of_match[] = {
  87         { .compatible = "atmel,sama5d2-flexcom" },
  88         { /* sentinel */ }
  89 };
  90 MODULE_DEVICE_TABLE(of, atmel_flexcom_of_match);
  91
  92 static struct platform_driver atmel_flexcom_driver = {
  93         .probe  = atmel_flexcom_probe,
  94         .driver = {
  95                 .name           = "atmel_flexcom",
  96                 .of_match_table = atmel_flexcom_of_match,
  97         },
  98 };
  99
 100 module_platform_driver(atmel_flexcom_driver);
 101
 102 MODULE_AUTHOR("Cyrille Pitchen <cyrille.pitchen@atmel.com>");
 103 MODULE_DESCRIPTION("Atmel Flexcom MFD driver");
 104 MODULE_LICENSE("GPL v2");