arch/arm/mach-omap2/hdq1w.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * IP block integration code for the HDQ1W/1-wire IP block
   4  *
   5  * Copyright (C) 2012 Texas Instruments, Inc.
   6  * Paul Walmsley
   7  *
   8  * Based on the I2C reset code in arch/arm/mach-omap2/i2c.c by
   9  *     Avinash.H.M <avinashhm@ti.com>
  10  */
  11
  12 #include <linux/kernel.h>
  13 #include <linux/init.h>
  14 #include <linux/err.h>
  15 #include <linux/platform_device.h>
  16
  17 #include "soc.h"
  18 #include "omap_hwmod.h"
  19 #include "omap_device.h"
  20 #include "hdq1w.h"
  21
  22 #include "prm.h"
  23 #include "common.h"
  24
  25 /**
  26  * omap_hdq1w_reset - reset the OMAP HDQ1W module
  27  * @oh: struct omap_hwmod *
  28  *
  29  * OCP soft reset the HDQ1W IP block.  Section 20.6.1.4 "HDQ1W/1-Wire
  30  * Software Reset" of the OMAP34xx Technical Reference Manual Revision
  31  * ZR (SWPU223R) does not include the rather important fact that, for
  32  * the reset to succeed, the HDQ1W module's internal clock gate must be
  33  * programmed to allow the clock to propagate to the rest of the
  34  * module.  In this sense, it's rather similar to the I2C custom reset
  35  * function.  Returns 0.
  36  */
  37 int omap_hdq1w_reset(struct omap_hwmod *oh)
  38 {
  39         u32 v;
  40         int c = 0;
  41
  42         /* Write to the SOFTRESET bit */
  43         omap_hwmod_softreset(oh);
  44
  45         /* Enable the module's internal clocks */
  46         v = omap_hwmod_read(oh, HDQ_CTRL_STATUS_OFFSET);
  47         v |= 1 << HDQ_CTRL_STATUS_CLOCKENABLE_SHIFT;
  48         omap_hwmod_write(v, oh, HDQ_CTRL_STATUS_OFFSET);
  49
  50         /* Poll on RESETDONE bit */
  51         omap_test_timeout((omap_hwmod_read(oh,
  52                                            oh->class->sysc->syss_offs)
  53                            & SYSS_RESETDONE_MASK),
  54                           MAX_MODULE_SOFTRESET_WAIT, c);
  55
  56         if (c == MAX_MODULE_SOFTRESET_WAIT)
  57                 pr_warn("%s: %s: softreset failed (waited %d usec)\n",
  58                         __func__, oh->name, MAX_MODULE_SOFTRESET_WAIT);
  59         else
  60                 pr_debug("%s: %s: softreset in %d usec\n", __func__,
  61                          oh->name, c);
  62
  63         return 0;
  64 }