clk: tegra: Add closed loop support for the DFLL
authorTuomas Tynkkynen <ttynkkynen@nvidia.com>
Wed, 13 May 2015 14:58:37 +0000 (17:58 +0300)
committerThierry Reding <treding@nvidia.com>
Thu, 16 Jul 2015 07:32:46 +0000 (09:32 +0200)
With closed loop support, the clock rate of the DFLL can be adjusted.

The oscillator itself in the DFLL is a free-running oscillator whose
rate is directly determined the supply voltage. However, the DFLL
module contains logic to compare the DFLL output rate to a fixed
reference clock (51 MHz) and make a decision to either lower or raise
the DFLL supply voltage. The DFLL module can then autonomously change
the supply voltage by communicating with an off-chip PMIC via either I2C
or PWM signals. This driver currently supports only I2C.

Signed-off-by: Tuomas Tynkkynen <ttynkkynen@nvidia.com>
Signed-off-by: Mikko Perttunen <mikko.perttunen@kapsi.fi>
Acked-by: Peter De Schrijver <pdeschrijver@nvidia.com>
Acked-by: Michael Turquette <mturquette@linaro.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>
drivers/clk/tegra/clk-dfll.c

index fb138bfa0af291c9f6ed6c932e02ab559d6f9ced..6ec645776897d7759db5c97ec6dd70fa6497a956 100644 (file)
  */
 #define REF_CLOCK_RATE                 51000000UL
 
+#define DVCO_RATE_TO_MULT(rate, ref_rate)      ((rate) / ((ref_rate) / 2))
+#define MULT_TO_DVCO_RATE(mult, ref_rate)      ((mult) * ((ref_rate) / 2))
 
 /**
  * enum dfll_ctrl_mode - DFLL hardware operating mode
  * @DFLL_UNINITIALIZED: (uninitialized state - not in hardware bitfield)
  * @DFLL_DISABLED: DFLL not generating an output clock
  * @DFLL_OPEN_LOOP: DVCO running, but DFLL not adjusting voltage
+ * @DFLL_CLOSED_LOOP: DVCO running, and DFLL adjusting voltage to match
+ *                   the requested rate
  *
  * The integer corresponding to the last two states, minus one, is
  * written to the DFLL hardware to change operating modes.
@@ -220,6 +224,7 @@ enum dfll_ctrl_mode {
        DFLL_UNINITIALIZED = 0,
        DFLL_DISABLED = 1,
        DFLL_OPEN_LOOP = 2,
+       DFLL_CLOSED_LOOP = 3,
 };
 
 /**
@@ -237,6 +242,22 @@ enum dfll_tune_range {
        DFLL_TUNE_LOW = 1,
 };
 
+/**
+ * struct dfll_rate_req - target DFLL rate request data
+ * @rate: target frequency, after the postscaling
+ * @dvco_target_rate: target frequency, after the postscaling
+ * @lut_index: LUT index at which voltage the dvco_target_rate will be reached
+ * @mult_bits: value to program to the MULT bits of the DFLL_FREQ_REQ register
+ * @scale_bits: value to program to the SCALE bits of the DFLL_FREQ_REQ register
+ */
+struct dfll_rate_req {
+       unsigned long rate;
+       unsigned long dvco_target_rate;
+       int lut_index;
+       u8 mult_bits;
+       u8 scale_bits;
+};
+
 struct tegra_dfll {
        struct device                   *dev;
        struct tegra_dfll_soc_data      *soc;
@@ -261,9 +282,27 @@ struct tegra_dfll {
        struct dentry                   *debugfs_dir;
        struct clk_hw                   dfll_clk_hw;
        const char                      *output_clock_name;
+       struct dfll_rate_req            last_req;
+       unsigned long                   last_unrounded_rate;
 
        /* Parameters from DT */
        u32                             droop_ctrl;
+       u32                             sample_rate;
+       u32                             force_mode;
+       u32                             cf;
+       u32                             ci;
+       u32                             cg;
+       bool                            cg_scale;
+
+       /* I2C interface parameters */
+       u32                             i2c_fs_rate;
+       u32                             i2c_reg;
+       u32                             i2c_slave_addr;
+
+       /* i2c_lut array entries are regulator framework selectors */
+       unsigned                        i2c_lut[MAX_DFLL_VOLTAGES];
+       int                             i2c_lut_size;
+       u8                              lut_min, lut_max, lut_safe;
 };
 
 #define clk_hw_to_dfll(_hw) container_of(_hw, struct tegra_dfll, dfll_clk_hw)
@@ -273,6 +312,7 @@ static const char * const mode_name[] = {
        [DFLL_UNINITIALIZED] = "uninitialized",
        [DFLL_DISABLED] = "disabled",
        [DFLL_OPEN_LOOP] = "open_loop",
+       [DFLL_CLOSED_LOOP] = "closed_loop",
 };
 
 /*
@@ -498,6 +538,283 @@ static void dfll_set_mode(struct tegra_dfll *td,
        dfll_wmb(td);
 }
 
+/*
+ * DFLL-to-I2C controller interface
+ */
+
+/**
+ * dfll_i2c_set_output_enabled - enable/disable I2C PMIC voltage requests
+ * @td: DFLL instance
+ * @enable: whether to enable or disable the I2C voltage requests
+ *
+ * Set the master enable control for I2C control value updates. If disabled,
+ * then I2C control messages are inhibited, regardless of the DFLL mode.
+ */
+static int dfll_i2c_set_output_enabled(struct tegra_dfll *td, bool enable)
+{
+       u32 val;
+
+       val = dfll_i2c_readl(td, DFLL_OUTPUT_CFG);
+
+       if (enable)
+               val |= DFLL_OUTPUT_CFG_I2C_ENABLE;
+       else
+               val &= ~DFLL_OUTPUT_CFG_I2C_ENABLE;
+
+       dfll_i2c_writel(td, val, DFLL_OUTPUT_CFG);
+       dfll_i2c_wmb(td);
+
+       return 0;
+}
+
+/**
+ * dfll_load_lut - load the voltage lookup table
+ * @td: struct tegra_dfll *
+ *
+ * Load the voltage-to-PMIC register value lookup table into the DFLL
+ * IP block memory. Look-up tables can be loaded at any time.
+ */
+static void dfll_load_i2c_lut(struct tegra_dfll *td)
+{
+       int i, lut_index;
+       u32 val;
+
+       for (i = 0; i < MAX_DFLL_VOLTAGES; i++) {
+               if (i < td->lut_min)
+                       lut_index = td->lut_min;
+               else if (i > td->lut_max)
+                       lut_index = td->lut_max;
+               else
+                       lut_index = i;
+
+                 val = regulator_list_hardware_vsel(td->vdd_reg,
+                                                    td->i2c_lut[lut_index]);
+               __raw_writel(val, td->lut_base + i * 4);
+       }
+
+       dfll_i2c_wmb(td);
+}
+
+/**
+ * dfll_init_i2c_if - set up the DFLL's DFLL-I2C interface
+ * @td: DFLL instance
+ *
+ * During DFLL driver initialization, program the DFLL-I2C interface
+ * with the PMU slave address, vdd register offset, and transfer mode.
+ * This data is used by the DFLL to automatically construct I2C
+ * voltage-set commands, which are then passed to the DFLL's internal
+ * I2C controller.
+ */
+static void dfll_init_i2c_if(struct tegra_dfll *td)
+{
+       u32 val;
+
+       if (td->i2c_slave_addr > 0x7f) {
+               val = td->i2c_slave_addr << DFLL_I2C_CFG_SLAVE_ADDR_SHIFT_10BIT;
+               val |= DFLL_I2C_CFG_SLAVE_ADDR_10;
+       } else {
+               val = td->i2c_slave_addr << DFLL_I2C_CFG_SLAVE_ADDR_SHIFT_7BIT;
+       }
+       val |= DFLL_I2C_CFG_SIZE_MASK;
+       val |= DFLL_I2C_CFG_ARB_ENABLE;
+       dfll_i2c_writel(td, val, DFLL_I2C_CFG);
+
+       dfll_i2c_writel(td, td->i2c_reg, DFLL_I2C_VDD_REG_ADDR);
+
+       val = DIV_ROUND_UP(td->i2c_clk_rate, td->i2c_fs_rate * 8);
+       BUG_ON(!val || (val > DFLL_I2C_CLK_DIVISOR_MASK));
+       val = (val - 1) << DFLL_I2C_CLK_DIVISOR_FS_SHIFT;
+
+       /* default hs divisor just in case */
+       val |= 1 << DFLL_I2C_CLK_DIVISOR_HS_SHIFT;
+       __raw_writel(val, td->i2c_controller_base + DFLL_I2C_CLK_DIVISOR);
+       dfll_i2c_wmb(td);
+}
+
+/**
+ * dfll_init_out_if - prepare DFLL-to-PMIC interface
+ * @td: DFLL instance
+ *
+ * During DFLL driver initialization or resume from context loss,
+ * disable the I2C command output to the PMIC, set safe voltage and
+ * output limits, and disable and clear limit interrupts.
+ */
+static void dfll_init_out_if(struct tegra_dfll *td)
+{
+       u32 val;
+
+       td->lut_min = 0;
+       td->lut_max = td->i2c_lut_size - 1;
+       td->lut_safe = td->lut_min + 1;
+
+       dfll_i2c_writel(td, 0, DFLL_OUTPUT_CFG);
+       val = (td->lut_safe << DFLL_OUTPUT_CFG_SAFE_SHIFT) |
+               (td->lut_max << DFLL_OUTPUT_CFG_MAX_SHIFT) |
+               (td->lut_min << DFLL_OUTPUT_CFG_MIN_SHIFT);
+       dfll_i2c_writel(td, val, DFLL_OUTPUT_CFG);
+       dfll_i2c_wmb(td);
+
+       dfll_writel(td, 0, DFLL_OUTPUT_FORCE);
+       dfll_i2c_writel(td, 0, DFLL_INTR_EN);
+       dfll_i2c_writel(td, DFLL_INTR_MAX_MASK | DFLL_INTR_MIN_MASK,
+                       DFLL_INTR_STS);
+
+       dfll_load_i2c_lut(td);
+       dfll_init_i2c_if(td);
+}
+
+/*
+ * Set/get the DFLL's targeted output clock rate
+ */
+
+/**
+ * find_lut_index_for_rate - determine I2C LUT index for given DFLL rate
+ * @td: DFLL instance
+ * @rate: clock rate
+ *
+ * Determines the index of a I2C LUT entry for a voltage that approximately
+ * produces the given DFLL clock rate. This is used when forcing a value
+ * to the integrator during rate changes. Returns -ENOENT if a suitable
+ * LUT index is not found.
+ */
+static int find_lut_index_for_rate(struct tegra_dfll *td, unsigned long rate)
+{
+       struct dev_pm_opp *opp;
+       int i, uv;
+
+       opp = dev_pm_opp_find_freq_ceil(td->soc->opp_dev, &rate);
+       if (IS_ERR(opp))
+               return PTR_ERR(opp);
+       uv = dev_pm_opp_get_voltage(opp);
+
+       for (i = 0; i < td->i2c_lut_size; i++) {
+               if (regulator_list_voltage(td->vdd_reg, td->i2c_lut[i]) == uv)
+                       return i;
+       }
+
+       return -ENOENT;
+}
+
+/**
+ * dfll_calculate_rate_request - calculate DFLL parameters for a given rate
+ * @td: DFLL instance
+ * @req: DFLL-rate-request structure
+ * @rate: the desired DFLL rate
+ *
+ * Populate the DFLL-rate-request record @req fields with the scale_bits
+ * and mult_bits fields, based on the target input rate. Returns 0 upon
+ * success, or -EINVAL if the requested rate in req->rate is too high
+ * or low for the DFLL to generate.
+ */
+static int dfll_calculate_rate_request(struct tegra_dfll *td,
+                                      struct dfll_rate_req *req,
+                                      unsigned long rate)
+{
+       u32 val;
+
+       /*
+        * If requested rate is below the minimum DVCO rate, active the scaler.
+        * In the future the DVCO minimum voltage should be selected based on
+        * chip temperature and the actual minimum rate should be calibrated
+        * at runtime.
+        */
+       req->scale_bits = DFLL_FREQ_REQ_SCALE_MAX - 1;
+       if (rate < td->dvco_rate_min) {
+               int scale;
+
+               scale = DIV_ROUND_CLOSEST(rate / 1000 * DFLL_FREQ_REQ_SCALE_MAX,
+                                         td->dvco_rate_min / 1000);
+               if (!scale) {
+                       dev_err(td->dev, "%s: Rate %lu is too low\n",
+                               __func__, rate);
+                       return -EINVAL;
+               }
+               req->scale_bits = scale - 1;
+               rate = td->dvco_rate_min;
+       }
+
+       /* Convert requested rate into frequency request and scale settings */
+       val = DVCO_RATE_TO_MULT(rate, td->ref_rate);
+       if (val > FREQ_MAX) {
+               dev_err(td->dev, "%s: Rate %lu is above dfll range\n",
+                       __func__, rate);
+               return -EINVAL;
+       }
+       req->mult_bits = val;
+       req->dvco_target_rate = MULT_TO_DVCO_RATE(req->mult_bits, td->ref_rate);
+       req->rate = dfll_scale_dvco_rate(req->scale_bits,
+                                        req->dvco_target_rate);
+       req->lut_index = find_lut_index_for_rate(td, req->dvco_target_rate);
+       if (req->lut_index < 0)
+               return req->lut_index;
+
+       return 0;
+}
+
+/**
+ * dfll_set_frequency_request - start the frequency change operation
+ * @td: DFLL instance
+ * @req: rate request structure
+ *
+ * Tell the DFLL to try to change its output frequency to the
+ * frequency represented by @req. DFLL must be in closed-loop mode.
+ */
+static void dfll_set_frequency_request(struct tegra_dfll *td,
+                                      struct dfll_rate_req *req)
+{
+       u32 val = 0;
+       int force_val;
+       int coef = 128; /* FIXME: td->cg_scale? */;
+
+       force_val = (req->lut_index - td->lut_safe) * coef / td->cg;
+       force_val = clamp(force_val, FORCE_MIN, FORCE_MAX);
+
+       val |= req->mult_bits << DFLL_FREQ_REQ_MULT_SHIFT;
+       val |= req->scale_bits << DFLL_FREQ_REQ_SCALE_SHIFT;
+       val |= ((u32)force_val << DFLL_FREQ_REQ_FORCE_SHIFT) &
+               DFLL_FREQ_REQ_FORCE_MASK;
+       val |= DFLL_FREQ_REQ_FREQ_VALID | DFLL_FREQ_REQ_FORCE_ENABLE;
+
+       dfll_writel(td, val, DFLL_FREQ_REQ);
+       dfll_wmb(td);
+}
+
+/**
+ * tegra_dfll_request_rate - set the next rate for the DFLL to tune to
+ * @td: DFLL instance
+ * @rate: clock rate to target
+ *
+ * Convert the requested clock rate @rate into the DFLL control logic
+ * settings. In closed-loop mode, update new settings immediately to
+ * adjust DFLL output rate accordingly. Otherwise, just save them
+ * until the next switch to closed loop. Returns 0 upon success,
+ * -EPERM if the DFLL driver has not yet been initialized, or -EINVAL
+ * if @rate is outside the DFLL's tunable range.
+ */
+static int dfll_request_rate(struct tegra_dfll *td, unsigned long rate)
+{
+       int ret;
+       struct dfll_rate_req req;
+
+       if (td->mode == DFLL_UNINITIALIZED) {
+               dev_err(td->dev, "%s: Cannot set DFLL rate in %s mode\n",
+                       __func__, mode_name[td->mode]);
+               return -EPERM;
+       }
+
+       ret = dfll_calculate_rate_request(td, &req, rate);
+       if (ret)
+               return ret;
+
+       td->last_unrounded_rate = rate;
+       td->last_req = req;
+
+       if (td->mode == DFLL_CLOSED_LOOP)
+               dfll_set_frequency_request(td, &td->last_req);
+
+       return 0;
+}
+
 /*
  * DFLL enable/disable & open-loop <-> closed-loop transitions
  */
@@ -570,8 +887,76 @@ static void dfll_set_open_loop_config(struct tegra_dfll *td)
        dfll_wmb(td);
 }
 
+/**
+ * tegra_dfll_lock - switch from open-loop to closed-loop mode
+ * @td: DFLL instance
+ *
+ * Switch from OPEN_LOOP state to CLOSED_LOOP state. Returns 0 upon success,
+ * -EINVAL if the DFLL's target rate hasn't been set yet, or -EPERM if the
+ * DFLL is not currently in open-loop mode.
+ */
+static int dfll_lock(struct tegra_dfll *td)
+{
+       struct dfll_rate_req *req = &td->last_req;
+
+       switch (td->mode) {
+       case DFLL_CLOSED_LOOP:
+               return 0;
+
+       case DFLL_OPEN_LOOP:
+               if (req->rate == 0) {
+                       dev_err(td->dev, "%s: Cannot lock DFLL at rate 0\n",
+                               __func__);
+                       return -EINVAL;
+               }
+
+               dfll_i2c_set_output_enabled(td, true);
+               dfll_set_mode(td, DFLL_CLOSED_LOOP);
+               dfll_set_frequency_request(td, req);
+               return 0;
+
+       default:
+               BUG_ON(td->mode > DFLL_CLOSED_LOOP);
+               dev_err(td->dev, "%s: Cannot lock DFLL in %s mode\n",
+                       __func__, mode_name[td->mode]);
+               return -EPERM;
+       }
+}
+
+/**
+ * tegra_dfll_unlock - switch from closed-loop to open-loop mode
+ * @td: DFLL instance
+ *
+ * Switch from CLOSED_LOOP state to OPEN_LOOP state. Returns 0 upon success,
+ * or -EPERM if the DFLL is not currently in open-loop mode.
+ */
+static int dfll_unlock(struct tegra_dfll *td)
+{
+       switch (td->mode) {
+       case DFLL_CLOSED_LOOP:
+               dfll_set_open_loop_config(td);
+               dfll_set_mode(td, DFLL_OPEN_LOOP);
+               dfll_i2c_set_output_enabled(td, false);
+               return 0;
+
+       case DFLL_OPEN_LOOP:
+               return 0;
+
+       default:
+               BUG_ON(td->mode > DFLL_CLOSED_LOOP);
+               dev_err(td->dev, "%s: Cannot unlock DFLL in %s mode\n",
+                       __func__, mode_name[td->mode]);
+               return -EPERM;
+       }
+}
+
 /*
  * Clock framework integration
+ *
+ * When the DFLL is being controlled by the CCF, always enter closed loop
+ * mode when the clk is enabled. This requires that a DFLL rate request
+ * has been set beforehand, which implies that a clk_set_rate() call is
+ * always required before a clk_enable().
  */
 
 static int dfll_clk_is_enabled(struct clk_hw *hw)
@@ -584,21 +969,72 @@ static int dfll_clk_is_enabled(struct clk_hw *hw)
 static int dfll_clk_enable(struct clk_hw *hw)
 {
        struct tegra_dfll *td = clk_hw_to_dfll(hw);
+       int ret;
+
+       ret = dfll_enable(td);
+       if (ret)
+               return ret;
+
+       ret = dfll_lock(td);
+       if (ret)
+               dfll_disable(td);
 
-       return dfll_enable(td);
+       return ret;
 }
 
 static void dfll_clk_disable(struct clk_hw *hw)
+{
+       struct tegra_dfll *td = clk_hw_to_dfll(hw);
+       int ret;
+
+       ret = dfll_unlock(td);
+       if (!ret)
+               dfll_disable(td);
+}
+
+static unsigned long dfll_clk_recalc_rate(struct clk_hw *hw,
+                                         unsigned long parent_rate)
 {
        struct tegra_dfll *td = clk_hw_to_dfll(hw);
 
-       dfll_disable(td);
+       return td->last_unrounded_rate;
+}
+
+static long dfll_clk_round_rate(struct clk_hw *hw,
+                               unsigned long rate,
+                               unsigned long *parent_rate)
+{
+       struct tegra_dfll *td = clk_hw_to_dfll(hw);
+       struct dfll_rate_req req;
+       int ret;
+
+       ret = dfll_calculate_rate_request(td, &req, rate);
+       if (ret)
+               return ret;
+
+       /*
+        * Don't return the rounded rate, since it doesn't really matter as
+        * the output rate will be voltage controlled anyway, and cpufreq
+        * freaks out if any rounding happens.
+        */
+       return rate;
+}
+
+static int dfll_clk_set_rate(struct clk_hw *hw, unsigned long rate,
+                            unsigned long parent_rate)
+{
+       struct tegra_dfll *td = clk_hw_to_dfll(hw);
+
+       return dfll_request_rate(td, rate);
 }
 
 static const struct clk_ops dfll_clk_ops = {
        .is_enabled     = dfll_clk_is_enabled,
        .enable         = dfll_clk_enable,
        .disable        = dfll_clk_disable,
+       .recalc_rate    = dfll_clk_recalc_rate,
+       .round_rate     = dfll_clk_round_rate,
+       .set_rate       = dfll_clk_set_rate,
 };
 
 static struct clk_init_data dfll_clk_init_data = {
@@ -677,6 +1113,23 @@ static int attr_enable_set(void *data, u64 val)
 DEFINE_SIMPLE_ATTRIBUTE(enable_fops, attr_enable_get, attr_enable_set,
                        "%llu\n");
 
+static int attr_lock_get(void *data, u64 *val)
+{
+       struct tegra_dfll *td = data;
+
+       *val = (td->mode == DFLL_CLOSED_LOOP);
+
+       return 0;
+}
+static int attr_lock_set(void *data, u64 val)
+{
+       struct tegra_dfll *td = data;
+
+       return val ? dfll_lock(td) :  dfll_unlock(td);
+}
+DEFINE_SIMPLE_ATTRIBUTE(lock_fops, attr_lock_get, attr_lock_set,
+                       "%llu\n");
+
 static int attr_rate_get(void *data, u64 *val)
 {
        struct tegra_dfll *td = data;
@@ -685,7 +1138,14 @@ static int attr_rate_get(void *data, u64 *val)
 
        return 0;
 }
-DEFINE_SIMPLE_ATTRIBUTE(rate_fops, attr_rate_get, NULL, "%llu\n");
+
+static int attr_rate_set(void *data, u64 val)
+{
+       struct tegra_dfll *td = data;
+
+       return dfll_request_rate(td, val);
+}
+DEFINE_SIMPLE_ATTRIBUTE(rate_fops, attr_rate_get, attr_rate_set, "%llu\n");
 
 static int attr_registers_show(struct seq_file *s, void *data)
 {
@@ -751,6 +1211,10 @@ static int dfll_debug_init(struct tegra_dfll *td)
                                 td->debugfs_dir, td, &enable_fops))
                goto err_out;
 
+       if (!debugfs_create_file("lock", S_IRUGO,
+                                td->debugfs_dir, td, &lock_fops))
+               goto err_out;
+
        if (!debugfs_create_file("rate", S_IRUGO,
                                 td->debugfs_dir, td, &rate_fops))
                goto err_out;
@@ -782,6 +1246,19 @@ err_out:
  */
 static void dfll_set_default_params(struct tegra_dfll *td)
 {
+       u32 val;
+
+       val = DIV_ROUND_UP(td->ref_rate, td->sample_rate * 32);
+       BUG_ON(val > DFLL_CONFIG_DIV_MASK);
+       dfll_writel(td, val, DFLL_CONFIG);
+
+       val = (td->force_mode << DFLL_PARAMS_FORCE_MODE_SHIFT) |
+               (td->cf << DFLL_PARAMS_CF_PARAM_SHIFT) |
+               (td->ci << DFLL_PARAMS_CI_PARAM_SHIFT) |
+               (td->cg << DFLL_PARAMS_CG_PARAM_SHIFT) |
+               (td->cg_scale ? DFLL_PARAMS_CG_SCALE : 0);
+       dfll_writel(td, val, DFLL_PARAMS);
+
        dfll_tune_low(td);
        dfll_writel(td, td->droop_ctrl, DFLL_DROOP_CTRL);
        dfll_writel(td, DFLL_MONITOR_CTRL_FREQ, DFLL_MONITOR_CTRL);
@@ -859,6 +1336,8 @@ static int dfll_init(struct tegra_dfll *td)
                goto di_err2;
        }
 
+       td->last_unrounded_rate = 0;
+
        pm_runtime_enable(td->dev);
        pm_runtime_get_sync(td->dev);
 
@@ -870,6 +1349,8 @@ static int dfll_init(struct tegra_dfll *td)
 
        dfll_set_open_loop_config(td);
 
+       dfll_init_out_if(td);
+
        pm_runtime_put_sync(td->dev);
 
        return 0;
@@ -888,6 +1369,130 @@ di_err1:
  * DT data fetch
  */
 
+/*
+ * Find a PMIC voltage register-to-voltage mapping for the given voltage.
+ * An exact voltage match is required.
+ */
+static int find_vdd_map_entry_exact(struct tegra_dfll *td, int uV)
+{
+       int i, n_voltages, reg_uV;
+
+       n_voltages = regulator_count_voltages(td->vdd_reg);
+       for (i = 0; i < n_voltages; i++) {
+               reg_uV = regulator_list_voltage(td->vdd_reg, i);
+               if (reg_uV < 0)
+                       break;
+
+               if (uV == reg_uV)
+                       return i;
+       }
+
+       dev_err(td->dev, "no voltage map entry for %d uV\n", uV);
+       return -EINVAL;
+}
+
+/*
+ * Find a PMIC voltage register-to-voltage mapping for the given voltage,
+ * rounding up to the closest supported voltage.
+ * */
+static int find_vdd_map_entry_min(struct tegra_dfll *td, int uV)
+{
+       int i, n_voltages, reg_uV;
+
+       n_voltages = regulator_count_voltages(td->vdd_reg);
+       for (i = 0; i < n_voltages; i++) {
+               reg_uV = regulator_list_voltage(td->vdd_reg, i);
+               if (reg_uV < 0)
+                       break;
+
+               if (uV <= reg_uV)
+                       return i;
+       }
+
+       dev_err(td->dev, "no voltage map entry rounding to %d uV\n", uV);
+       return -EINVAL;
+}
+
+/**
+ * dfll_build_i2c_lut - build the I2C voltage register lookup table
+ * @td: DFLL instance
+ *
+ * The DFLL hardware has 33 bytes of look-up table RAM that must be filled with
+ * PMIC voltage register values that span the entire DFLL operating range.
+ * This function builds the look-up table based on the OPP table provided by
+ * the soc-specific platform driver (td->soc->opp_dev) and the PMIC
+ * register-to-voltage mapping queried from the regulator framework.
+ *
+ * On success, fills in td->i2c_lut and returns 0, or -err on failure.
+ */
+static int dfll_build_i2c_lut(struct tegra_dfll *td)
+{
+       int ret = -EINVAL;
+       int j, v, v_max, v_opp;
+       int selector;
+       unsigned long rate;
+       struct dev_pm_opp *opp;
+
+       rcu_read_lock();
+
+       rate = ULONG_MAX;
+       opp = dev_pm_opp_find_freq_floor(td->soc->opp_dev, &rate);
+       if (IS_ERR(opp)) {
+               dev_err(td->dev, "couldn't get vmax opp, empty opp table?\n");
+               goto out;
+       }
+       v_max = dev_pm_opp_get_voltage(opp);
+
+       v = td->soc->min_millivolts * 1000;
+       td->i2c_lut[0] = find_vdd_map_entry_exact(td, v);
+       if (td->i2c_lut[0] < 0)
+               goto out;
+
+       for (j = 1, rate = 0; ; rate++) {
+               opp = dev_pm_opp_find_freq_ceil(td->soc->opp_dev, &rate);
+               if (IS_ERR(opp))
+                       break;
+               v_opp = dev_pm_opp_get_voltage(opp);
+
+               if (v_opp <= td->soc->min_millivolts * 1000)
+                       td->dvco_rate_min = dev_pm_opp_get_freq(opp);
+
+               for (;;) {
+                       v += max(1, (v_max - v) / (MAX_DFLL_VOLTAGES - j));
+                       if (v >= v_opp)
+                               break;
+
+                       selector = find_vdd_map_entry_min(td, v);
+                       if (selector < 0)
+                               goto out;
+                       if (selector != td->i2c_lut[j - 1])
+                               td->i2c_lut[j++] = selector;
+               }
+
+               v = (j == MAX_DFLL_VOLTAGES - 1) ? v_max : v_opp;
+               selector = find_vdd_map_entry_exact(td, v);
+               if (selector < 0)
+                       goto out;
+               if (selector != td->i2c_lut[j - 1])
+                       td->i2c_lut[j++] = selector;
+
+               if (v >= v_max)
+                       break;
+       }
+       td->i2c_lut_size = j;
+
+       if (!td->dvco_rate_min)
+               dev_err(td->dev, "no opp above DFLL minimum voltage %d mV\n",
+                       td->soc->min_millivolts);
+       else
+               ret = 0;
+
+out:
+       rcu_read_unlock();
+
+       return ret;
+}
+
 /**
  * read_dt_param - helper function for reading required parameters from the DT
  * @td: DFLL instance
@@ -911,6 +1516,50 @@ static bool read_dt_param(struct tegra_dfll *td, const char *param, u32 *dest)
        return true;
 }
 
+/**
+ * dfll_fetch_i2c_params - query PMIC I2C params from DT & regulator subsystem
+ * @td: DFLL instance
+ *
+ * Read all the parameters required for operation in I2C mode. The parameters
+ * can originate from the device tree or the regulator subsystem.
+ * Returns 0 on success or -err on failure.
+ */
+static int dfll_fetch_i2c_params(struct tegra_dfll *td)
+{
+       struct regmap *regmap;
+       struct device *i2c_dev;
+       struct i2c_client *i2c_client;
+       int vsel_reg, vsel_mask;
+       int ret;
+
+       if (!read_dt_param(td, "nvidia,i2c-fs-rate", &td->i2c_fs_rate))
+               return -EINVAL;
+
+       regmap = regulator_get_regmap(td->vdd_reg);
+       i2c_dev = regmap_get_device(regmap);
+       i2c_client = to_i2c_client(i2c_dev);
+
+       td->i2c_slave_addr = i2c_client->addr;
+
+       ret = regulator_get_hardware_vsel_register(td->vdd_reg,
+                                                  &vsel_reg,
+                                                  &vsel_mask);
+       if (ret < 0) {
+               dev_err(td->dev,
+                       "regulator unsuitable for DFLL I2C operation\n");
+               return -EINVAL;
+       }
+       td->i2c_reg = vsel_reg;
+
+       ret = dfll_build_i2c_lut(td);
+       if (ret) {
+               dev_err(td->dev, "couldn't build I2C LUT\n");
+               return ret;
+       }
+
+       return 0;
+}
+
 /**
  * dfll_fetch_common_params - read DFLL parameters from the device tree
  * @td: DFLL instance
@@ -923,6 +1572,13 @@ static int dfll_fetch_common_params(struct tegra_dfll *td)
        bool ok = true;
 
        ok &= read_dt_param(td, "nvidia,droop-ctrl", &td->droop_ctrl);
+       ok &= read_dt_param(td, "nvidia,sample-rate", &td->sample_rate);
+       ok &= read_dt_param(td, "nvidia,force-mode", &td->force_mode);
+       ok &= read_dt_param(td, "nvidia,cf", &td->cf);
+       ok &= read_dt_param(td, "nvidia,ci", &td->ci);
+       ok &= read_dt_param(td, "nvidia,cg", &td->cg);
+       td->cg_scale = of_property_read_bool(td->dev->of_node,
+                                            "nvidia,cg-scale");
 
        if (of_property_read_string(td->dev->of_node, "clock-output-names",
                                    &td->output_clock_name)) {
@@ -984,6 +1640,10 @@ int tegra_dfll_register(struct platform_device *pdev,
                return ret;
        }
 
+       ret = dfll_fetch_i2c_params(td);
+       if (ret)
+               return ret;
+
        mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (!mem) {
                dev_err(td->dev, "no control register resource\n");