kernel/drivers/clk/sunxi/clk-sun6i-ar100.c

   1 /*
   2  * Copyright (C) 2014 Free Electrons
   3  *
   4  * License Terms: GNU General Public License v2
   5  * Author: Boris BREZILLON <boris.brezillon@free-electrons.com>
   6  *
   7  * Allwinner A31 AR100 clock driver
   8  *
   9  */
  10
  11 #include <linux/clk-provider.h>
  12 #include <linux/module.h>
  13 #include <linux/of.h>
  14 #include <linux/platform_device.h>
  15
  16 #define SUN6I_AR100_MAX_PARENTS         4
  17 #define SUN6I_AR100_SHIFT_MASK          0x3
  18 #define SUN6I_AR100_SHIFT_MAX           SUN6I_AR100_SHIFT_MASK
  19 #define SUN6I_AR100_SHIFT_SHIFT         4
  20 #define SUN6I_AR100_DIV_MASK            0x1f
  21 #define SUN6I_AR100_DIV_MAX             (SUN6I_AR100_DIV_MASK + 1)
  22 #define SUN6I_AR100_DIV_SHIFT           8
  23 #define SUN6I_AR100_MUX_MASK            0x3
  24 #define SUN6I_AR100_MUX_SHIFT           16
  25
  26 struct ar100_clk {
  27         struct clk_hw hw;
  28         void __iomem *reg;
  29 };
  30
  31 static inline struct ar100_clk *to_ar100_clk(struct clk_hw *hw)
  32 {
  33         return container_of(hw, struct ar100_clk, hw);
  34 }
  35
  36 static unsigned long ar100_recalc_rate(struct clk_hw *hw,
  37                                        unsigned long parent_rate)
  38 {
  39         struct ar100_clk *clk = to_ar100_clk(hw);
  40         u32 val = readl(clk->reg);
  41         int shift = (val >> SUN6I_AR100_SHIFT_SHIFT) & SUN6I_AR100_SHIFT_MASK;
  42         int div = (val >> SUN6I_AR100_DIV_SHIFT) & SUN6I_AR100_DIV_MASK;
  43
  44         return (parent_rate >> shift) / (div + 1);
  45 }
  46
  47 static int ar100_determine_rate(struct clk_hw *hw,
  48                                 struct clk_rate_request *req)
  49 {
  50         int nparents = clk_hw_get_num_parents(hw);
  51         long best_rate = -EINVAL;
  52         int i;
  53
  54         req->best_parent_hw = NULL;
  55
  56         for (i = 0; i < nparents; i++) {
  57                 unsigned long parent_rate;
  58                 unsigned long tmp_rate;
  59                 struct clk_hw *parent;
  60                 unsigned long div;
  61                 int shift;
  62
  63                 parent = clk_hw_get_parent_by_index(hw, i);
  64                 parent_rate = clk_hw_get_rate(parent);
  65                 div = DIV_ROUND_UP(parent_rate, req->rate);
  66
  67                 /*
  68                  * The AR100 clk contains 2 divisors:
  69                  * - one power of 2 divisor
  70                  * - one regular divisor
  71                  *
  72                  * First check if we can safely shift (or divide by a power
  73                  * of 2) without losing precision on the requested rate.
  74                  */
  75                 shift = ffs(div) - 1;
  76                 if (shift > SUN6I_AR100_SHIFT_MAX)
  77                         shift = SUN6I_AR100_SHIFT_MAX;
  78
  79                 div >>= shift;
  80
  81                 /*
  82                  * Then if the divisor is still bigger than what the HW
  83                  * actually supports, use a bigger shift (or power of 2
  84                  * divider) value and accept to lose some precision.
  85                  */
  86                 while (div > SUN6I_AR100_DIV_MAX) {
  87                         shift++;
  88                         div >>= 1;
  89                         if (shift > SUN6I_AR100_SHIFT_MAX)
  90                                 break;
  91                 }
  92
  93                 /*
  94                  * If the shift value (or power of 2 divider) is bigger
  95                  * than what the HW actually support, skip this parent.
  96                  */
  97                 if (shift > SUN6I_AR100_SHIFT_MAX)
  98                         continue;
  99
 100                 tmp_rate = (parent_rate >> shift) / div;
 101                 if (!req->best_parent_hw || tmp_rate > best_rate) {
 102                         req->best_parent_hw = parent;
 103                         req->best_parent_rate = parent_rate;
 104                         best_rate = tmp_rate;
 105                 }
 106         }
 107
 108         if (best_rate < 0)
 109                 return best_rate;
 110
 111         req->rate = best_rate;
 112
 113         return 0;
 114 }
 115
 116 static int ar100_set_parent(struct clk_hw *hw, u8 index)
 117 {
 118         struct ar100_clk *clk = to_ar100_clk(hw);
 119         u32 val = readl(clk->reg);
 120
 121         if (index >= SUN6I_AR100_MAX_PARENTS)
 122                 return -EINVAL;
 123
 124         val &= ~(SUN6I_AR100_MUX_MASK << SUN6I_AR100_MUX_SHIFT);
 125         val |= (index << SUN6I_AR100_MUX_SHIFT);
 126         writel(val, clk->reg);
 127
 128         return 0;
 129 }
 130
 131 static u8 ar100_get_parent(struct clk_hw *hw)
 132 {
 133         struct ar100_clk *clk = to_ar100_clk(hw);
 134         return (readl(clk->reg) >> SUN6I_AR100_MUX_SHIFT) &
 135                SUN6I_AR100_MUX_MASK;
 136 }
 137
 138 static int ar100_set_rate(struct clk_hw *hw, unsigned long rate,
 139                           unsigned long parent_rate)
 140 {
 141         unsigned long div = parent_rate / rate;
 142         struct ar100_clk *clk = to_ar100_clk(hw);
 143         u32 val = readl(clk->reg);
 144         int shift;
 145
 146         if (parent_rate % rate)
 147                 return -EINVAL;
 148
 149         shift = ffs(div) - 1;
 150         if (shift > SUN6I_AR100_SHIFT_MAX)
 151                 shift = SUN6I_AR100_SHIFT_MAX;
 152
 153         div >>= shift;
 154
 155         if (div > SUN6I_AR100_DIV_MAX)
 156                 return -EINVAL;
 157
 158         val &= ~((SUN6I_AR100_SHIFT_MASK << SUN6I_AR100_SHIFT_SHIFT) |
 159                  (SUN6I_AR100_DIV_MASK << SUN6I_AR100_DIV_SHIFT));
 160         val |= (shift << SUN6I_AR100_SHIFT_SHIFT) |
 161                (div << SUN6I_AR100_DIV_SHIFT);
 162         writel(val, clk->reg);
 163
 164         return 0;
 165 }
 166
 167 static struct clk_ops ar100_ops = {
 168         .recalc_rate = ar100_recalc_rate,
 169         .determine_rate = ar100_determine_rate,
 170         .set_parent = ar100_set_parent,
 171         .get_parent = ar100_get_parent,
 172         .set_rate = ar100_set_rate,
 173 };
 174
 175 static int sun6i_a31_ar100_clk_probe(struct platform_device *pdev)
 176 {
 177         const char *parents[SUN6I_AR100_MAX_PARENTS];
 178         struct device_node *np = pdev->dev.of_node;
 179         const char *clk_name = np->name;
 180         struct clk_init_data init;
 181         struct ar100_clk *ar100;
 182         struct resource *r;
 183         struct clk *clk;
 184         int nparents;
 185
 186         ar100 = devm_kzalloc(&pdev->dev, sizeof(*ar100), GFP_KERNEL);
 187         if (!ar100)
 188                 return -ENOMEM;
 189
 190         r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 191         ar100->reg = devm_ioremap_resource(&pdev->dev, r);
 192         if (IS_ERR(ar100->reg))
 193                 return PTR_ERR(ar100->reg);
 194
 195         nparents = of_clk_get_parent_count(np);
 196         if (nparents > SUN6I_AR100_MAX_PARENTS)
 197                 nparents = SUN6I_AR100_MAX_PARENTS;
 198
 199         of_clk_parent_fill(np, parents, nparents);
 200
 201         of_property_read_string(np, "clock-output-names", &clk_name);
 202
 203         init.name = clk_name;
 204         init.ops = &ar100_ops;
 205         init.parent_names = parents;
 206         init.num_parents = nparents;
 207         init.flags = 0;
 208
 209         ar100->hw.init = &init;
 210
 211         clk = clk_register(&pdev->dev, &ar100->hw);
 212         if (IS_ERR(clk))
 213                 return PTR_ERR(clk);
 214
 215         return of_clk_add_provider(np, of_clk_src_simple_get, clk);
 216 }
 217
 218 static const struct of_device_id sun6i_a31_ar100_clk_dt_ids[] = {
 219         { .compatible = "allwinner,sun6i-a31-ar100-clk" },
 220         { /* sentinel */ }
 221 };
 222 MODULE_DEVICE_TABLE(of, sun6i_a31_ar100_clk_dt_ids);
 223
 224 static struct platform_driver sun6i_a31_ar100_clk_driver = {
 225         .driver = {
 226                 .name = "sun6i-a31-ar100-clk",
 227                 .of_match_table = sun6i_a31_ar100_clk_dt_ids,
 228         },
 229         .probe = sun6i_a31_ar100_clk_probe,
 230 };
 231 module_platform_driver(sun6i_a31_ar100_clk_driver);
 232
 233 MODULE_AUTHOR("Boris BREZILLON <boris.brezillon@free-electrons.com>");
 234 MODULE_DESCRIPTION("Allwinner A31 AR100 clock Driver");
 235 MODULE_LICENSE("GPL v2");