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Date: Tue, 5 May 2015 15:16:08 -0400
From: Rhyland Klein <rklein@nvidia.com>
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To: Benson Leung <bleung@chromium.org>
CC: Peter De Schrijver <pdeschrijver@nvidia.com>,
        Mike Turquette <mturquette@linaro.org>,
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        Thierry Reding <thierry.reding@gmail.com>,
        Alexandre Courbot <gnurou@gmail.com>, <linux-clk@vger.kernel.org>,
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        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4 08/20] clk: tegra: pll: Add logic for handling SDM
 data
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On 5/4/2015 7:01 PM, Benson Leung wrote:
> On Mon, May 4, 2015 at 9:37 AM, Rhyland Klein <rklein@nvidia.com> wrote:
>> @@ -495,6 +505,28 @@ static int _calc_rate(struct clk_hw *hw, struct tegra_clk_pll_freq_table *cfg,
>>         return 0;
>>  }
>>
>> +static void clk_pll_set_sdm_data(struct clk_hw *hw,
>> +                                struct tegra_clk_pll_freq_table *cfg)
>> +{
>> +       struct tegra_clk_pll *pll = to_clk_pll(hw);
>> +       u32 val;
>> +
>> +       if (!pll->params->sdm_din_reg)
>> +               return;
>> +
>> +       if (cfg->sdm_data) {
>> +               val = pll_readl_sdm_din(pll) & (~sdm_din_mask(pll));
>> +               val |= sdin_data_to_din(cfg->sdm_data) & sdm_din_mask(pll);
>> +               pll_writel_sdm_din(val, pll);
>> +       }
>> +
>> +       val = pll_readl_sdm_ctrl(pll);
>> +       if (!cfg->sdm_data != !(val & pll->params->sdm_ctrl_en_mask)) {
> 
> You can use sdm_en_mask(pll) here.
> 
> I'm not super clear about what you're trying to accomplish here with
> !cfg->sdm_data != !(val & mask).
> Are you just checking if the masked value is different from sdm_data,
> but accounting for the integer widths being different (u16 vs u32)?

So I got clarification from the downstream author to be sure, and this
is the answer to what this is checking:

(<Configuration has non zero  SDM_DATA>  AND <sdm control is disabled>)
OR
(<Configuration has zero  SDM_DATA>  AND <sdm control is enabled>)

So the check is correct, just a complicated way of expressing it.

-rhyland


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