Re: [PATCH v3 05/11] clk: tegra: prepare dfll driver for PWM regulator

[Peter De Schrijver <pdeschrijver@nvidia.com>]

On Mon, Mar 12, 2018 at 11:08:51AM +0000, Jon Hunter wrote:
> 
> On 12/03/18 09:14, Peter De Schrijver wrote:
> > On Thu, Mar 08, 2018 at 10:50:06PM +0000, Jon Hunter wrote:
> >>
> >> On 06/02/18 16:34, Peter De Schrijver wrote:
> >>> This patch prepares the dfll driver to work with PWM regulators.
> >>> To do this we introduce a new array lut_uv which gives the voltage for
> >>> a given index generated by the dfll logic. This index will then be
> >>> translated to a PMIC voltage ID in case of I2C using the i2c_lut. In case
> >>> of a PWM regulator, it will be used to determine the PWM duty cycle.
> >>> We also introduce lut_bottom which holds the lowest voltage we will ever
> >>> need. In case of I2C this can be set to zero because the i2c_lut will be
> >>> initialized such that entry 0 will be the lowest voltage we will ever
> >>> need. In case of PWM, the lowest voltage is determined by the regulator
> >>> hardware so we need this software limit. Note that this is different
> >>> from lut_min which gives the lowest voltage we allow taking temperature
> >>> into account. In a future patchset we will update lut_vmin dynamically.
> >>> Similarly lut_max will be the highest voltage allowed taking temperature
> >>> into accouint. Also this will be updated dynamically once temperature
> >>> dependence will be introduced.
> >>>
> >>> Signed-off-by: Peter De Schrijver <pdeschrijver@nvidia.com>
> >>> ---
> >>>  drivers/clk/tegra/clk-dfll.c | 62 ++++++++++++++++++++++++++------------------
> >>>  1 file changed, 37 insertions(+), 25 deletions(-)
> >>>
> >>> diff --git a/drivers/clk/tegra/clk-dfll.c b/drivers/clk/tegra/clk-dfll.c
> >>> index 0a7deee..fa97763 100644
> >>> --- a/drivers/clk/tegra/clk-dfll.c
> >>> +++ b/drivers/clk/tegra/clk-dfll.c
> >>> @@ -301,9 +301,10 @@ struct tegra_dfll {
> >>>  	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;
> >>> +	unsigned int			i2c_lut[MAX_DFLL_VOLTAGES];
> >>> +	unsigned int			lut_uv[MAX_DFLL_VOLTAGES];
> >>> +	int				lut_size;
> >>> +	u8				lut_bottom, lut_min, lut_max, lut_safe;
> >>>  };
> >>>  
> >>>  #define clk_hw_to_dfll(_hw) container_of(_hw, struct tegra_dfll, dfll_clk_hw)
> >>> @@ -531,10 +532,10 @@ static void dfll_load_i2c_lut(struct tegra_dfll *td)
> >>>  	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;
> >>> +		if (i < td->lut_bottom)
> >>> +			lut_index = td->lut_bottom;
> >>> +		else if (i > td->lut_size - 1)
> >>> +			lut_index = td->lut_size - 1;
> >>>  		else
> >>>  			lut_index = i;
> >>>  
> >>> @@ -594,9 +595,9 @@ 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;
> >>> +	td->lut_min = td->lut_bottom;
> >>> +	td->lut_max = td->lut_size - 1;
> >>> +	td->lut_safe = td->lut_min + (td->lut_min < td->lut_max ? 1 : 0);
> >>>  
> >>>  	dfll_i2c_writel(td, 0, DFLL_OUTPUT_CFG);
> >>>  	val = (td->lut_safe << DFLL_OUTPUT_CFG_SAFE_SHIFT) |
> >>> @@ -619,11 +620,11 @@ static void dfll_init_out_if(struct tegra_dfll *td)
> >>>   */
> >>>  
> >>>  /**
> >>> - * find_lut_index_for_rate - determine I2C LUT index for given DFLL rate
> >>> + * find_lut_index_for_rate - determine 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
> >>> + * Determines the index of a 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.
> >>> @@ -637,11 +638,11 @@ static int find_lut_index_for_rate(struct tegra_dfll *td, unsigned long rate)
> >>>  	if (IS_ERR(opp))
> >>>  		return PTR_ERR(opp);
> >>>  
> >>> -	uv = dev_pm_opp_get_voltage(opp);
> >>> +	uv = dev_pm_opp_get_voltage(opp) / td->soc->alignment.step_uv;
> >>>  	dev_pm_opp_put(opp);
> >>>  
> >>> -	for (i = 0; i < td->i2c_lut_size; i++) {
> >>> -		if (regulator_list_voltage(td->vdd_reg, td->i2c_lut[i]) == uv)
> >>> +	for (i = td->lut_bottom; i < td->lut_size; i++) {
> >>> +		if ((td->lut_uv[i] / td->soc->alignment.step_uv) >= uv)
> >>>  			return i;
> >>>  	}
> >>>  
> >>> @@ -1377,15 +1378,17 @@ static int dfll_init(struct tegra_dfll *td)
> >>>   */
> >>>  static int find_vdd_map_entry_exact(struct tegra_dfll *td, int uV)
> >>>  {
> >>> -	int i, n_voltages, reg_uV;
> >>> +	int i, n_voltages, reg_mult, align_mult;
> >>>  
> >>> +	align_mult = uV / td->soc->alignment.step_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)
> >>> +		reg_mult = regulator_list_voltage(td->vdd_reg, i) /
> >>> +				td->soc->alignment.step_uv;
> >>> +		if (reg_mult < 0)
> >>>  			break;
> >>>  
> >>> -		if (uV == reg_uV)
> >>> +		if (align_mult == reg_mult)
> >>>  			return i;
> >>>  	}
> >>>  
> >>> @@ -1399,15 +1402,17 @@ static int find_vdd_map_entry_exact(struct tegra_dfll *td, int uV)
> >>>   * */
> >>>  static int find_vdd_map_entry_min(struct tegra_dfll *td, int uV)
> >>>  {
> >>> -	int i, n_voltages, reg_uV;
> >>> +	int i, n_voltages, reg_mult, align_mult;
> >>>  
> >>> +	align_mult = uV / td->soc->alignment.step_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)
> >>> +		reg_mult = regulator_list_voltage(td->vdd_reg, i) /
> >>> +				td->soc->alignment.step_uv;
> >>> +		if (reg_mult < 0)
> >>>  			break;
> >>>  
> >>> -		if (uV <= reg_uV)
> >>> +		if (align_mult <= reg_mult)
> >>>  			return i;
> >>>  	}
> >>>  
> >>> @@ -1450,8 +1455,10 @@ static int dfll_build_i2c_lut(struct tegra_dfll *td)
> >>>  	if (lut < 0)
> >>>  		goto out;
> >>>  	td->i2c_lut[0] = lut;
> >>> +	td->lut_bottom = 0;
> >>>  
> >>>  	for (j = 1, rate = 0; ; rate++) {
> >>> +
> >>>  		opp = dev_pm_opp_find_freq_ceil(td->soc->dev, &rate);
> >>>  		if (IS_ERR(opp))
> >>>  			break;
> >>> @@ -1484,13 +1491,18 @@ static int dfll_build_i2c_lut(struct tegra_dfll *td)
> >>>  		if (v >= v_max)
> >>>  			break;
> >>>  	}
> >>> -	td->i2c_lut_size = j;
> >>> +	td->lut_size = j;
> >>>  
> >>>  	if (!td->dvco_rate_min)
> >>>  		dev_err(td->dev, "no opp above DFLL minimum voltage %d mV\n",
> >>>  			td->soc->cvb->min_millivolts);
> >>> -	else
> >>> +	else {
> >>>  		ret = 0;
> >>> +		for (j = 0; j < td->lut_size; j++)
> >>> +			td->lut_uv[j] =
> >>> +				regulator_list_voltage(td->vdd_reg,
> >>> +						       td->i2c_lut[j]);
> >>> +	}
> >>>  
> >>>  out:
> >>>  	return ret;
> >>>
> >>
> >> I am a bit confused by this patch as I don't fully understand from the
> >> description what is being changed. For example, there are a few places
> >> where you are dividing by td->soc->alignment.step_uv, which seems to be
> >> changing the calculations/behaviour for I2C unless I am missing something?
> >>
> > 
> > The goal is to use td->lut_uv for all voltage related lookups so we can unify
> > the code for i2c and PWM regulators.
> 
> Yes but looking at the patch there is more going on here than just that.
> Any changes to the exisiting i2c code should be a separate change unless
> I am completely misunderstanding you.
> 

This requires changes to the existing i2c code, which is what this patch does.

Peter.