drivers/clk/bcm/clk-raspberrypi.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Raspberry Pi driver for firmware controlled clocks
   4  *
   5  * Even though clk-bcm2835 provides an interface to the hardware registers for
   6  * the system clocks we've had to factor out 'pllb' as the firmware 'owns' it.
   7  * We're not allowed to change it directly as we might race with the
   8  * over-temperature and under-voltage protections provided by the firmware.
   9  *
  10  * Copyright (C) 2019 Nicolas Saenz Julienne <[email protected]>
  11  */
  12
  13 #include <linux/clkdev.h>
  14 #include <linux/clk-provider.h>
  15 #include <linux/io.h>
  16 #include <linux/module.h>
  17 #include <linux/platform_device.h>
  18
  19 #include <soc/bcm2835/raspberrypi-firmware.h>
  20
  21 #define RPI_FIRMWARE_ARM_CLK_ID         0x00000003
  22
  23 #define RPI_FIRMWARE_STATE_ENABLE_BIT   BIT(0)
  24 #define RPI_FIRMWARE_STATE_WAIT_BIT     BIT(1)
  25
  26 /*
  27  * Even though the firmware interface alters 'pllb' the frequencies are
  28  * provided as per 'pllb_arm'. We need to scale before passing them trough.
  29  */
  30 #define RPI_FIRMWARE_PLLB_ARM_DIV_RATE  2
  31
  32 #define A2W_PLL_FRAC_BITS               20
  33
  34 struct raspberrypi_clk {
  35         struct device *dev;
  36         struct rpi_firmware *firmware;
  37         struct platform_device *cpufreq;
  38
  39         unsigned long min_rate;
  40         unsigned long max_rate;
  41
  42         struct clk_hw pllb;
  43         struct clk_hw *pllb_arm;
  44         struct clk_lookup *pllb_arm_lookup;
  45 };
  46
  47 /*
  48  * Structure of the message passed to Raspberry Pi's firmware in order to
  49  * change clock rates. The 'disable_turbo' option is only available to the ARM
  50  * clock (pllb) which we enable by default as turbo mode will alter multiple
  51  * clocks at once.
  52  *
  53  * Even though we're able to access the clock registers directly we're bound to
  54  * use the firmware interface as the firmware ultimately takes care of
  55  * mitigating overheating/undervoltage situations and we would be changing
  56  * frequencies behind his back.
  57  *
  58  * For more information on the firmware interface check:
  59  * https://github.com/raspberrypi/firmware/wiki/Mailbox-property-interface
  60  */
  61 struct raspberrypi_firmware_prop {
  62         __le32 id;
  63         __le32 val;
  64         __le32 disable_turbo;
  65 } __packed;
  66
  67 static int raspberrypi_clock_property(struct rpi_firmware *firmware, u32 tag,
  68                                       u32 clk, u32 *val)
  69 {
  70         struct raspberrypi_firmware_prop msg = {
  71                 .id = cpu_to_le32(clk),
  72                 .val = cpu_to_le32(*val),
  73                 .disable_turbo = cpu_to_le32(1),
  74         };
  75         int ret;
  76
  77         ret = rpi_firmware_property(firmware, tag, &msg, sizeof(msg));
  78         if (ret)
  79                 return ret;
  80
  81         *val = le32_to_cpu(msg.val);
  82
  83         return 0;
  84 }
  85
  86 static int raspberrypi_fw_pll_is_on(struct clk_hw *hw)
  87 {
  88         struct raspberrypi_clk *rpi = container_of(hw, struct raspberrypi_clk,
  89                                                    pllb);
  90         u32 val = 0;
  91         int ret;
  92
  93         ret = raspberrypi_clock_property(rpi->firmware,
  94                                          RPI_FIRMWARE_GET_CLOCK_STATE,
  95                                          RPI_FIRMWARE_ARM_CLK_ID, &val);
  96         if (ret)
  97                 return 0;
  98
  99         return !!(val & RPI_FIRMWARE_STATE_ENABLE_BIT);
 100 }
 101
 102
 103 static unsigned long raspberrypi_fw_pll_get_rate(struct clk_hw *hw,
 104                                                  unsigned long parent_rate)
 105 {
 106         struct raspberrypi_clk *rpi = container_of(hw, struct raspberrypi_clk,
 107                                                    pllb);
 108         u32 val = 0;
 109         int ret;
 110
 111         ret = raspberrypi_clock_property(rpi->firmware,
 112                                          RPI_FIRMWARE_GET_CLOCK_RATE,
 113                                          RPI_FIRMWARE_ARM_CLK_ID,
 114                                          &val);
 115         if (ret)
 116                 return ret;
 117
 118         return val * RPI_FIRMWARE_PLLB_ARM_DIV_RATE;
 119 }
 120
 121 static int raspberrypi_fw_pll_set_rate(struct clk_hw *hw, unsigned long rate,
 122                                        unsigned long parent_rate)
 123 {
 124         struct raspberrypi_clk *rpi = container_of(hw, struct raspberrypi_clk,
 125                                                    pllb);
 126         u32 new_rate = rate / RPI_FIRMWARE_PLLB_ARM_DIV_RATE;
 127         int ret;
 128
 129         ret = raspberrypi_clock_property(rpi->firmware,
 130                                          RPI_FIRMWARE_SET_CLOCK_RATE,
 131                                          RPI_FIRMWARE_ARM_CLK_ID,
 132                                          &new_rate);
 133         if (ret)
 134                 dev_err_ratelimited(rpi->dev, "Failed to change %s frequency: %d",
 135                                     clk_hw_get_name(hw), ret);
 136
 137         return ret;
 138 }
 139
 140 /*
 141  * Sadly there is no firmware rate rounding interface. We borrowed it from
 142  * clk-bcm2835.
 143  */
 144 static int raspberrypi_pll_determine_rate(struct clk_hw *hw,
 145                                           struct clk_rate_request *req)
 146 {
 147         struct raspberrypi_clk *rpi = container_of(hw, struct raspberrypi_clk,
 148                                                    pllb);
 149         u64 div, final_rate;
 150         u32 ndiv, fdiv;
 151
 152         /* We can't use req->rate directly as it would overflow */
 153         final_rate = clamp(req->rate, rpi->min_rate, rpi->max_rate);
 154
 155         div = (u64)final_rate << A2W_PLL_FRAC_BITS;
 156         do_div(div, req->best_parent_rate);
 157
 158         ndiv = div >> A2W_PLL_FRAC_BITS;
 159         fdiv = div & ((1 << A2W_PLL_FRAC_BITS) - 1);
 160
 161         final_rate = ((u64)req->best_parent_rate *
 162                                         ((ndiv << A2W_PLL_FRAC_BITS) + fdiv));
 163
 164         req->rate = final_rate >> A2W_PLL_FRAC_BITS;
 165
 166         return 0;
 167 }
 168
 169 static const struct clk_ops raspberrypi_firmware_pll_clk_ops = {
 170         .is_prepared = raspberrypi_fw_pll_is_on,
 171         .recalc_rate = raspberrypi_fw_pll_get_rate,
 172         .set_rate = raspberrypi_fw_pll_set_rate,
 173         .determine_rate = raspberrypi_pll_determine_rate,
 174 };
 175
 176 static int raspberrypi_register_pllb(struct raspberrypi_clk *rpi)
 177 {
 178         u32 min_rate = 0, max_rate = 0;
 179         struct clk_init_data init;
 180         int ret;
 181
 182         memset(&init, 0, sizeof(init));
 183
 184         /* All of the PLLs derive from the external oscillator. */
 185         init.parent_names = (const char *[]){ "osc" };
 186         init.num_parents = 1;
 187         init.name = "pllb";
 188         init.ops = &raspberrypi_firmware_pll_clk_ops;
 189         init.flags = CLK_GET_RATE_NOCACHE | CLK_IGNORE_UNUSED;
 190
 191         /* Get min & max rates set by the firmware */
 192         ret = raspberrypi_clock_property(rpi->firmware,
 193                                          RPI_FIRMWARE_GET_MIN_CLOCK_RATE,
 194                                          RPI_FIRMWARE_ARM_CLK_ID,
 195                                          &min_rate);
 196         if (ret) {
 197                 dev_err(rpi->dev, "Failed to get %s min freq: %d\n",
 198                         init.name, ret);
 199                 return ret;
 200         }
 201
 202         ret = raspberrypi_clock_property(rpi->firmware,
 203                                          RPI_FIRMWARE_GET_MAX_CLOCK_RATE,
 204                                          RPI_FIRMWARE_ARM_CLK_ID,
 205                                          &max_rate);
 206         if (ret) {
 207                 dev_err(rpi->dev, "Failed to get %s max freq: %d\n",
 208                         init.name, ret);
 209                 return ret;
 210         }
 211
 212         if (!min_rate || !max_rate) {
 213                 dev_err(rpi->dev, "Unexpected frequency range: min %u, max %u\n",
 214                         min_rate, max_rate);
 215                 return -EINVAL;
 216         }
 217
 218         dev_info(rpi->dev, "CPU frequency range: min %u, max %u\n",
 219                  min_rate, max_rate);
 220
 221         rpi->min_rate = min_rate * RPI_FIRMWARE_PLLB_ARM_DIV_RATE;
 222         rpi->max_rate = max_rate * RPI_FIRMWARE_PLLB_ARM_DIV_RATE;
 223
 224         rpi->pllb.init = &init;
 225
 226         return devm_clk_hw_register(rpi->dev, &rpi->pllb);
 227 }
 228
 229 static int raspberrypi_register_pllb_arm(struct raspberrypi_clk *rpi)
 230 {
 231         rpi->pllb_arm = clk_hw_register_fixed_factor(rpi->dev,
 232                                 "pllb_arm", "pllb",
 233                                 CLK_SET_RATE_PARENT | CLK_GET_RATE_NOCACHE,
 234                                 1, 2);
 235         if (IS_ERR(rpi->pllb_arm)) {
 236                 dev_err(rpi->dev, "Failed to initialize pllb_arm\n");
 237                 return PTR_ERR(rpi->pllb_arm);
 238         }
 239
 240         rpi->pllb_arm_lookup = clkdev_hw_create(rpi->pllb_arm, NULL, "cpu0");
 241         if (!rpi->pllb_arm_lookup) {
 242                 dev_err(rpi->dev, "Failed to initialize pllb_arm_lookup\n");
 243                 clk_hw_unregister_fixed_factor(rpi->pllb_arm);
 244                 return -ENOMEM;
 245         }
 246
 247         return 0;
 248 }
 249
 250 static int raspberrypi_clk_probe(struct platform_device *pdev)
 251 {
 252         struct device_node *firmware_node;
 253         struct device *dev = &pdev->dev;
 254         struct rpi_firmware *firmware;
 255         struct raspberrypi_clk *rpi;
 256         int ret;
 257
 258         firmware_node = of_find_compatible_node(NULL, NULL,
 259                                         "raspberrypi,bcm2835-firmware");
 260         if (!firmware_node) {
 261                 dev_err(dev, "Missing firmware node\n");
 262                 return -ENOENT;
 263         }
 264
 265         firmware = rpi_firmware_get(firmware_node);
 266         of_node_put(firmware_node);
 267         if (!firmware)
 268                 return -EPROBE_DEFER;
 269
 270         rpi = devm_kzalloc(dev, sizeof(*rpi), GFP_KERNEL);
 271         if (!rpi)
 272                 return -ENOMEM;
 273
 274         rpi->dev = dev;
 275         rpi->firmware = firmware;
 276         platform_set_drvdata(pdev, rpi);
 277
 278         ret = raspberrypi_register_pllb(rpi);
 279         if (ret) {
 280                 dev_err(dev, "Failed to initialize pllb, %d\n", ret);
 281                 return ret;
 282         }
 283
 284         ret = raspberrypi_register_pllb_arm(rpi);
 285         if (ret)
 286                 return ret;
 287
 288         rpi->cpufreq = platform_device_register_data(dev, "raspberrypi-cpufreq",
 289                                                      -1, NULL, 0);
 290
 291         return 0;
 292 }
 293
 294 static int raspberrypi_clk_remove(struct platform_device *pdev)
 295 {
 296         struct raspberrypi_clk *rpi = platform_get_drvdata(pdev);
 297
 298         platform_device_unregister(rpi->cpufreq);
 299
 300         return 0;
 301 }
 302
 303 static struct platform_driver raspberrypi_clk_driver = {
 304         .driver = {
 305                 .name = "raspberrypi-clk",
 306         },
 307         .probe          = raspberrypi_clk_probe,
 308         .remove         = raspberrypi_clk_remove,
 309 };
 310 module_platform_driver(raspberrypi_clk_driver);
 311
 312 MODULE_AUTHOR("Nicolas Saenz Julienne <[email protected]>");
 313 MODULE_DESCRIPTION("Raspberry Pi firmware clock driver");
 314 MODULE_LICENSE("GPL");
 315 MODULE_ALIAS("platform:raspberrypi-clk");