1 /*
2  * OMAP36xx-specific clkops
3  *
4  * Copyright (C) 2010 Texas Instruments, Inc.
5  * Copyright (C) 2010 Nokia Corporation
6  *
7  * Mike Turquette
8  * Vijaykumar GN
9  * Paul Walmsley
10  *
11  * Parts of this code are based on code written by
12  * Richard Woodruff, Tony Lindgren, Tuukka Tikkanen, Karthik Dasu,
13  * Russell King
14  *
15  * This program is free software; you can redistribute it and/or modify
16  * it under the terms of the GNU General Public License version 2 as
17  * published by the Free Software Foundation.
18  */
19 #undef DEBUG
20 
21 #include <linux/kernel.h>
22 #include <linux/clk.h>
23 #include <linux/io.h>
24 
25 #include <plat/clock.h>
26 
27 #include "clock.h"
28 #include "clock36xx.h"
29 
30 
31 /**
32  * omap36xx_pwrdn_clk_enable_with_hsdiv_restore - enable clocks suffering
33  *         from HSDivider PWRDN problem Implements Errata ID: i556.
34  * @clk: DPLL output struct clk
35  *
36  * 3630 only: dpll3_m3_ck, dpll4_m2_ck, dpll4_m3_ck, dpll4_m4_ck,
37  * dpll4_m5_ck & dpll4_m6_ck dividers gets loaded with reset
38  * valueafter their respective PWRDN bits are set.  Any dummy write
39  * (Any other value different from the Read value) to the
40  * corresponding CM_CLKSEL register will refresh the dividers.
41  */
omap36xx_pwrdn_clk_enable_with_hsdiv_restore(struct clk * clk)42 static int omap36xx_pwrdn_clk_enable_with_hsdiv_restore(struct clk *clk)
43 {
44 	u32 dummy_v, orig_v, clksel_shift;
45 	int ret;
46 
47 	/* Clear PWRDN bit of HSDIVIDER */
48 	ret = omap2_dflt_clk_enable(clk);
49 
50 	/* Restore the dividers */
51 	if (!ret) {
52 		clksel_shift = __ffs(clk->parent->clksel_mask);
53 		orig_v = __raw_readl(clk->parent->clksel_reg);
54 		dummy_v = orig_v;
55 
56 		/* Write any other value different from the Read value */
57 		dummy_v ^= (1 << clksel_shift);
58 		__raw_writel(dummy_v, clk->parent->clksel_reg);
59 
60 		/* Write the original divider */
61 		__raw_writel(orig_v, clk->parent->clksel_reg);
62 	}
63 
64 	return ret;
65 }
66 
67 const struct clkops clkops_omap36xx_pwrdn_with_hsdiv_wait_restore = {
68 	.enable		= omap36xx_pwrdn_clk_enable_with_hsdiv_restore,
69 	.disable	= omap2_dflt_clk_disable,
70 	.find_companion	= omap2_clk_dflt_find_companion,
71 	.find_idlest	= omap2_clk_dflt_find_idlest,
72 };
73