RE: [PATCH v5] clk: tegra: Initialize UTMIPLL when enabling PLLU

[Rhyland Klein]

Jonathan, can you confirm replacing usleep_range(100, 200) with udelay(2) works for you?

-rhyland

-----Original Message-----
From: Thierry Reding [mailto:thierry.reding@xxxxxxxxx] 
Sent: Friday, June 17, 2016 11:24 AM
To: Jonathan Hunter
Cc: Rhyland Klein; Peter De Schrijver; Mike Turquette; Stephen Warren; Stephen Boyd; Alexandre Courbot; linux-clk@xxxxxxxxxxxxxxx; linux-tegra@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Andrew Bresticker
Subject: Re: [PATCH v5] clk: tegra: Initialize UTMIPLL when enabling PLLU

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On Fri, Jun 17, 2016 at 02:49:41PM +0100, Jon Hunter wrote:
> Hi Thierry,
> 
> On 26/05/16 17:41, Rhyland Klein wrote:
> > From: Andrew Bresticker <abrestic@xxxxxxxxxxxx>
> > 
> > Move the UTMIPLL initialization code form clk-tegra<chip>.c files 
> > into clk-pll.c. UTMIPLL was being configured and set in HW control 
> > right after registration. However, when the clock init_table is 
> > processed and child clks of PLLU are enabled, it will call in and 
> > enable PLLU as well, and initiate SW enabling sequence even though 
> > PLLU is already in HW control. This leads to getting UTMIPLL stuck with a SEQ_BUSY status.
> > 
> > Doing the initialization once during pllu_enable means we configure 
> > it properly into HW control.
> > 
> > A side effect of the commonization/localization of the UTMIPLL init 
> > code, is that it corrects some errors that were present for earlier 
> > generations. For instance, in clk-tegra124.c, it used to have:
> > 
> > define UTMIP_PLL_CFG1_ENABLE_DLY_COUNT(x) (((x) & 0x1f) << 6)
> > 
> > when the correct shift to use is present in the new version:
> > 
> > define UTMIP_PLL_CFG1_ENABLE_DLY_COUNT(x) (((x) & 0x1f) << 27)
> > 
> > which matches the Tegra124 TRM register definition.
> > 
> > Signed-off-by: Andrew Bresticker <abrestic@xxxxxxxxxxxx>
> > 
> > [rklein: Merged in some later fixes for potential deadlocks]
> > 
> > Signed-off-by: Rhyland Klein <rklein@xxxxxxxxxx>
> > ---
> > v5:
> >  - Initialized flags to 0 to avoid harmless spinlock warnings
> > 
> > v4:
> >  - Re-added examples in patch description
> > 
> > v3:
> >  - Flushed out description to describe this patch.
> > 
> >  drivers/clk/tegra/clk-pll.c      | 484 +++++++++++++++++++++++++++++++++++++++
> >  drivers/clk/tegra/clk-tegra114.c | 155 +------------  
> > drivers/clk/tegra/clk-tegra124.c | 156 +------------  
> > drivers/clk/tegra/clk-tegra210.c | 182 +--------------  
> > drivers/clk/tegra/clk-tegra30.c  | 113 +--------
> >  drivers/clk/tegra/clk.h          |  17 ++
> >  6 files changed, 510 insertions(+), 597 deletions(-)
> > 
> > diff --git a/drivers/clk/tegra/clk-pll.c 
> > b/drivers/clk/tegra/clk-pll.c index 4e194ecc8d5e..31e20110fae4 
> > 100644
> > --- a/drivers/clk/tegra/clk-pll.c
> > +++ b/drivers/clk/tegra/clk-pll.c
> 
> ...
> 
> > +static int clk_pllu_tegra210_enable(struct clk_hw *hw) {
> > +	struct tegra_clk_pll *pll = to_clk_pll(hw);
> > +	struct clk_hw *pll_ref = clk_hw_get_parent(hw);
> > +	struct clk_hw *osc = clk_hw_get_parent(pll_ref);
> > +	unsigned long flags = 0, input_rate;
> > +	unsigned int i;
> > +	int ret = 0;
> > +	u32 val;
> > +
> > +	if (!osc) {
> > +		pr_err("%s: failed to get OSC clock\n", __func__);
> > +		return -EINVAL;
> > +	}
> > +	input_rate = clk_hw_get_rate(osc);
> > +
> > +	if (pll->lock)
> > +		spin_lock_irqsave(pll->lock, flags);
> > +
> > +	_clk_pll_enable(hw);
> > +	ret = clk_pll_wait_for_lock(pll);
> > +	if (ret < 0)
> > +		goto out;
> > +
> > +	for (i = 0; i < ARRAY_SIZE(utmi_parameters); i++) {
> > +		if (input_rate == utmi_parameters[i].osc_frequency)
> > +			break;
> > +	}
> > +
> > +	if (i == ARRAY_SIZE(utmi_parameters)) {
> > +		pr_err("%s: Unexpected input rate %lu\n", __func__, input_rate);
> > +		ret = -EINVAL;
> > +		goto out;
> > +	}
> > +
> > +	val = pll_readl_base(pll);
> > +	val &= ~PLLU_BASE_OVERRIDE;
> > +	pll_writel_base(val, pll);
> > +
> > +	/* Put PLLU under HW control */
> > +	val = readl_relaxed(pll->clk_base + PLLU_HW_PWRDN_CFG0);
> > +	val |= PLLU_HW_PWRDN_CFG0_IDDQ_PD_INCLUDE |
> > +	       PLLU_HW_PWRDN_CFG0_USE_SWITCH_DETECT |
> > +	       PLLU_HW_PWRDN_CFG0_USE_LOCKDET;
> > +	val &= ~(PLLU_HW_PWRDN_CFG0_CLK_ENABLE_SWCTL |
> > +		  PLLU_HW_PWRDN_CFG0_CLK_SWITCH_SWCTL);
> > +	writel_relaxed(val, pll->clk_base + PLLU_HW_PWRDN_CFG0);
> > +
> > +	val = readl_relaxed(pll->clk_base + XUSB_PLL_CFG0);
> > +	val &= ~XUSB_PLL_CFG0_PLLU_LOCK_DLY;
> > +	writel_relaxed(val, pll->clk_base + XUSB_PLL_CFG0);
> > +	udelay(1);
> > +
> > +	val = readl_relaxed(pll->clk_base + PLLU_HW_PWRDN_CFG0);
> > +	val |= PLLU_HW_PWRDN_CFG0_SEQ_ENABLE;
> > +	writel_relaxed(val, pll->clk_base + PLLU_HW_PWRDN_CFG0);
> > +	udelay(1);
> > +
> > +	/* Disable PLLU clock branch to UTMIPLL since it uses OSC */
> > +	val = pll_readl_base(pll);
> > +	val &= ~PLLU_BASE_CLKENABLE_USB;
> > +	pll_writel_base(val, pll);
> > +
> > +	val = readl_relaxed(pll->clk_base + UTMIPLL_HW_PWRDN_CFG0);
> > +	if (val & UTMIPLL_HW_PWRDN_CFG0_SEQ_ENABLE) {
> > +		pr_debug("UTMIPLL already enabled\n");
> > +		goto out;
> > +	}
> > +	val &= ~UTMIPLL_HW_PWRDN_CFG0_IDDQ_OVERRIDE;
> > +	writel_relaxed(val, pll->clk_base + UTMIPLL_HW_PWRDN_CFG0);
> > +
> > +	/* Program UTMIP PLL stable and active counts */
> > +	val = readl_relaxed(pll->clk_base + UTMIP_PLL_CFG2);
> > +	val &= ~UTMIP_PLL_CFG2_STABLE_COUNT(~0);
> > +	val |= UTMIP_PLL_CFG2_STABLE_COUNT(utmi_parameters[i].stable_count);
> > +	val &= ~UTMIP_PLL_CFG2_ACTIVE_DLY_COUNT(~0);
> > +	val |= UTMIP_PLL_CFG2_ACTIVE_DLY_COUNT(
> > +			utmi_parameters[i].active_delay_count);
> > +	val |= UTMIP_PLL_CFG2_PHY_XTAL_CLOCKEN;
> > +	writel_relaxed(val, pll->clk_base + UTMIP_PLL_CFG2);
> > +
> > +	/* Program UTMIP PLL delay and oscillator frequency counts */
> > +	val = readl_relaxed(pll->clk_base + UTMIP_PLL_CFG1);
> > +	val &= ~UTMIP_PLL_CFG1_ENABLE_DLY_COUNT(~0);
> > +	val |= UTMIP_PLL_CFG1_ENABLE_DLY_COUNT(
> > +		utmi_parameters[i].enable_delay_count);
> > +	val &= ~UTMIP_PLL_CFG1_XTAL_FREQ_COUNT(~0);
> > +	val |= UTMIP_PLL_CFG1_XTAL_FREQ_COUNT(
> > +		utmi_parameters[i].xtal_freq_count);
> > +	writel_relaxed(val, pll->clk_base + UTMIP_PLL_CFG1);
> > +
> > +	/* Remove power downs from UTMIP PLL control bits */
> > +	val = readl_relaxed(pll->clk_base + UTMIP_PLL_CFG1);
> > +	val &= ~UTMIP_PLL_CFG1_FORCE_PLL_ENABLE_POWERDOWN;
> > +	val |= UTMIP_PLL_CFG1_FORCE_PLL_ENABLE_POWERUP;
> > +	writel_relaxed(val, pll->clk_base + UTMIP_PLL_CFG1);
> > +	udelay(100);
> 
> In next-20160617 I see that this udelay is now a usleep_range(100, 
> 200) and this is causing the following splat when the clock is 
> enabled. I don't think that we can use usleep here ...

Okay, I'll back out the patch. I'd really prefer to avoid busy-looping for 100 microseconds here, so can we please find another way to do this?

Thierry

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