1 /*
2  * OMAP IP block custom reset and preprogramming stubs
3  *
4  * Copyright (C) 2012 Texas Instruments, Inc.
5  * Paul Walmsley
6  *
7  * A small number of IP blocks need custom reset and preprogramming
8  * functions.  The stubs in this file provide a standard way for the
9  * hwmod code to call these functions, which are to be located under
10  * drivers/.
11  *
12  * This program is free software; you can redistribute it and/or
13  * modify it under the terms of the GNU General Public License as
14  * published by the Free Software Foundation version 2.
15  *
16  * This program is distributed "as is" WITHOUT ANY WARRANTY of any
17  * kind, whether express or implied; without even the implied warranty
18  * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
19  * GNU General Public License for more details.
20  *
21  * You should have received a copy of the GNU General Public License
22  * along with this program; if not, write to the Free Software
23  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
24  * 02110-1301 USA
25  */
26 #include <linux/kernel.h>
27 #include <linux/errno.h>
28 
29 #include "omap_hwmod.h"
30 #include "common.h"
31 
32 #define OMAP_RTC_STATUS_REG	0x44
33 #define OMAP_RTC_KICK0_REG	0x6c
34 #define OMAP_RTC_KICK1_REG	0x70
35 
36 #define OMAP_RTC_KICK0_VALUE	0x83E70B13
37 #define OMAP_RTC_KICK1_VALUE	0x95A4F1E0
38 #define OMAP_RTC_STATUS_BUSY	BIT(0)
39 #define OMAP_RTC_MAX_READY_TIME	50
40 
41 /**
42  * omap_rtc_wait_not_busy - Wait for the RTC BUSY flag
43  * @oh: struct omap_hwmod *
44  *
45  * For updating certain RTC registers, the MPU must wait
46  * for the BUSY status in OMAP_RTC_STATUS_REG to become zero.
47  * Once the BUSY status is zero, there is a 15 microseconds access
48  * period in which the MPU can program.
49  */
omap_rtc_wait_not_busy(struct omap_hwmod * oh)50 static void omap_rtc_wait_not_busy(struct omap_hwmod *oh)
51 {
52 	int i;
53 
54 	/* BUSY may stay active for 1/32768 second (~30 usec) */
55 	omap_test_timeout(omap_hwmod_read(oh, OMAP_RTC_STATUS_REG)
56 			  & OMAP_RTC_STATUS_BUSY, OMAP_RTC_MAX_READY_TIME, i);
57 	/* now we have ~15 microseconds to read/write various registers */
58 }
59 
60 /**
61  * omap_hwmod_rtc_unlock - Unlock the Kicker mechanism.
62  * @oh: struct omap_hwmod *
63  *
64  * RTC IP have kicker feature. This prevents spurious writes to its registers.
65  * In order to write into any of the RTC registers, KICK values has te be
66  * written in respective KICK registers. This is needed for hwmod to write into
67  * sysconfig register.
68  */
omap_hwmod_rtc_unlock(struct omap_hwmod * oh)69 void omap_hwmod_rtc_unlock(struct omap_hwmod *oh)
70 {
71 	unsigned long flags;
72 
73 	local_irq_save(flags);
74 	omap_rtc_wait_not_busy(oh);
75 	omap_hwmod_write(OMAP_RTC_KICK0_VALUE, oh, OMAP_RTC_KICK0_REG);
76 	omap_hwmod_write(OMAP_RTC_KICK1_VALUE, oh, OMAP_RTC_KICK1_REG);
77 	local_irq_restore(flags);
78 }
79 
80 /**
81  * omap_hwmod_rtc_lock - Lock the Kicker mechanism.
82  * @oh: struct omap_hwmod *
83  *
84  * RTC IP have kicker feature. This prevents spurious writes to its registers.
85  * Once the RTC registers are written, KICK mechanism needs to be locked,
86  * in order to prevent any spurious writes. This function locks back the RTC
87  * registers once hwmod completes its write into sysconfig register.
88  */
omap_hwmod_rtc_lock(struct omap_hwmod * oh)89 void omap_hwmod_rtc_lock(struct omap_hwmod *oh)
90 {
91 	unsigned long flags;
92 
93 	local_irq_save(flags);
94 	omap_rtc_wait_not_busy(oh);
95 	omap_hwmod_write(0x0, oh, OMAP_RTC_KICK0_REG);
96 	omap_hwmod_write(0x0, oh, OMAP_RTC_KICK1_REG);
97 	local_irq_restore(flags);
98 }
99