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Subject: Re: [PATCH v3 05/11] clk: tegra: prepare dfll driver for PWM
 regulator
To:     Peter De Schrijver <pdeschrijver@nvidia.com>
CC:     <linux-tegra@vger.kernel.org>, <linux-clk@vger.kernel.org>,
        <mturquette@baylibre.com>, <sboyd@codeaurora.org>,
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From:   Jon Hunter <jonathanh@nvidia.com>
Message-ID: <a96b567f-eafe-ae3e-b90c-29a1e38d9aee@nvidia.com>
Date:   Tue, 13 Mar 2018 10:07:12 +0000
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On 13/03/18 09:03, Peter De Schrijver wrote:
> 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.

Yes and that maybe necessary, but it is unclear why. Can the i2c related
changes be made in a separate patch to isolate them?

Cheers
Jon

-- 
nvpublic