xref: /linux/arch/arm/mach-omap2/hdq1w.c (revision 75bf465f0bc33e9b776a46d6a1b9b990f5fb7c37)
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  */
omap_hdq1w_reset(struct omap_hwmod * oh)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 }
65