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Date: Mon, 10 Feb 2020 11:26:38 +0530
From: Vinod Koul <vkoul@...nel.org>
To: Stephen Boyd <sboyd@...nel.org>
Cc: agross@...nel.org, bjorn.andersson@...aro.org,
devicetree@...r.kernel.org, jshriram@...eaurora.org,
linux-arm-kernel@...ts.infradead.org,
linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
linux-kernel@...r.kernel.org, mark.rutland@....com,
mturquette@...libre.com, psodagud@...eaurora.org,
robh+dt@...nel.org, tdas@...eaurora.org, tsoni@...eaurora.org,
vnkgutta@...eaurora.org
Subject: Re: [PATCH v2 4/7] clk: qcom: clk-alpha-pll: Add support for
controlling Lucid PLLs
On 05-02-20, 11:33, Stephen Boyd wrote:
> Quoting Venkata Narendra Kumar Gutta (2020-01-24 14:32:24)
> > diff --git a/drivers/clk/qcom/clk-alpha-pll.c b/drivers/clk/qcom/clk-alpha-pll.c
> > index 1b073b2..4258ab0 100644
> > --- a/drivers/clk/qcom/clk-alpha-pll.c
> > +++ b/drivers/clk/qcom/clk-alpha-pll.c
> > @@ -1367,3 +1388,172 @@ static int clk_alpha_pll_postdiv_fabia_set_rate(struct clk_hw *hw,
> > .set_rate = clk_alpha_pll_postdiv_fabia_set_rate,
> > };
> > EXPORT_SYMBOL_GPL(clk_alpha_pll_postdiv_fabia_ops);
> > +
> > +void clk_lucid_pll_configure(struct clk_alpha_pll *pll, struct regmap *regmap,
>
> Can we get some kernel documentation for this function?
Okay adding
> > +{
> > + if (config->l)
> > + regmap_write(regmap, PLL_L_VAL(pll), config->l);
> > +
> > + regmap_write(regmap, PLL_CAL_L_VAL(pll), LUCID_PLL_CAL_VAL);
> > +
> > + if (config->alpha)
> > + regmap_write(regmap, PLL_ALPHA_VAL(pll), config->alpha);
> > +
> > + if (config->config_ctl_val)
> > + regmap_write(regmap, PLL_CONFIG_CTL(pll),
> > + config->config_ctl_val);
> > +
> > + if (config->config_ctl_hi_val)
> > + regmap_write(regmap, PLL_CONFIG_CTL_U(pll),
> > + config->config_ctl_hi_val);
> > +
> > + if (config->config_ctl_hi1_val)
> > + regmap_write(regmap, PLL_CONFIG_CTL_U1(pll),
> > + config->config_ctl_hi1_val);
> > +
> > + if (config->user_ctl_val)
> > + regmap_write(regmap, PLL_USER_CTL(pll),
> > + config->user_ctl_val);
> > +
> > + if (config->user_ctl_hi_val)
> > + regmap_write(regmap, PLL_USER_CTL_U(pll),
> > + config->user_ctl_hi_val);
> > +
> > + if (config->user_ctl_hi1_val)
> > + regmap_write(regmap, PLL_USER_CTL_U1(pll),
> > + config->user_ctl_hi1_val);
> > +
> > + if (config->test_ctl_val)
> > + regmap_write(regmap, PLL_TEST_CTL(pll),
> > + config->test_ctl_val);
> > +
> > + if (config->test_ctl_hi_val)
> > + regmap_write(regmap, PLL_TEST_CTL_U(pll),
> > + config->test_ctl_hi_val);
> > +
> > + if (config->test_ctl_hi1_val)
> > + regmap_write(regmap, PLL_TEST_CTL_U1(pll),
> > + config->test_ctl_hi1_val);
> > +
> > + regmap_update_bits(regmap, PLL_MODE(pll), PLL_UPDATE_BYPASS,
> > + PLL_UPDATE_BYPASS);
> > +
> > + /* Disable PLL output */
> > + regmap_update_bits(regmap, PLL_MODE(pll), PLL_OUTCTRL, 0);
> > +
> > + /* Set operation mode to OFF */
> > + regmap_write(regmap, PLL_OPMODE(pll), PLL_STANDBY);
> > +
> > + /* PLL should be in OFF mode before continuing */
> > + wmb();
>
> How does the write above overtake the write below? This barrier looks
> wrong.
I think you are correct, it doesnt :), so removing this
> > +static int alpha_pll_lucid_prepare(struct clk_hw *hw)
> > +{
> > + struct clk_alpha_pll *pll = to_clk_alpha_pll(hw);
> > + u32 regval;
> > + int ret;
> > +
> > + /* Return early if calibration is not needed. */
> > + regmap_read(pll->clkr.regmap, PLL_STATUS(pll), ®val);
> > + if (regval & LUCID_PCAL_DONE)
> > + return 0;
> > +
> > + ret = clk_trion_pll_enable(hw);
> > + if (ret)
> > + return ret;
> > +
> > + clk_trion_pll_disable(hw);
> > +
> > + return 0;
>
> Can you write this like:
>
> /* On/off to calibrate */
> ret = clk_trion_pll_enable(hw);
> if (!ret)
> clk_trion_pll_disable(hw);
>
> return ret;
Looks better, updated now.
> > +static int alpha_pll_lucid_set_rate(struct clk_hw *hw, unsigned long rate,
> > + unsigned long prate)
> > +{
> > + struct clk_alpha_pll *pll = to_clk_alpha_pll(hw);
> > + unsigned long rrate;
> > + u32 regval, l, alpha_width = pll_alpha_width(pll);
> > + u64 a;
> > + int ret;
> > +
> > + rrate = alpha_pll_round_rate(rate, prate, &l, &a, alpha_width);
> > +
> > + /*
> > + * Due to a limited number of bits for fractional rate programming, the
> > + * rounded up rate could be marginally higher than the requested rate.
> > + */
> > + if (rrate > (rate + PLL_RATE_MARGIN) || rrate < rate) {
>
> Any chance this can be pushed into the alpha_pll_round_rate() API? It's
> duplicated in this driver.
Yes here and couple of fabia pll functions. Said that I see
alpha_pll_round_rate() is also invoked two places,
alpha_pll_fabia_set_rate() and __clk_alpha_pll_set_rate(), so should we
let these two also be updated, if you are okay with that I will update
this
> > + regmap_write(pll->clkr.regmap, PLL_L_VAL(pll), l);
> > + regmap_write(pll->clkr.regmap, PLL_ALPHA_VAL(pll), a);
> > +
> > + /* Latch the PLL input */
> > + ret = regmap_update_bits(pll->clkr.regmap, PLL_MODE(pll),
> > + PLL_UPDATE, PLL_UPDATE);
> > + if (ret)
> > + return ret;
> > +
> > + /* Wait for 2 reference cycles before checking the ACK bit. */
>
> Are reference cycles 2 * 1 / 19.2MHz?
Will check and update on this
>
> > + udelay(1);
> > + regmap_read(pll->clkr.regmap, PLL_MODE(pll), ®val);
> > + if (!(regval & ALPHA_PLL_ACK_LATCH)) {
> > + WARN(1, "PLL latch failed. Output may be unstable!\n");
>
> Do we need a big WARN stack for this? How about pr_warn() instead?
Nope :), will move to a warn print :)
--
~Vinod
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