Date:	Thu, 30 Jun 2016 17:37:04 +0200
From:	Thierry Reding <thierry.reding@...il.com>
To:	Rhyland Klein <rklein@...dia.com>
Cc:	Jon Hunter <jonathanh@...dia.com>,
	Peter De Schrijver <pdeschrijver@...dia.com>,
	Mike Turquette <mturquette@...libre.com>,
	Stephen Warren <swarren@...dotorg.org>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Alexandre Courbot <gnurou@...il.com>,
	linux-clk@...r.kernel.org, linux-tegra@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Andrew Bresticker <abrestic@...omium.org>
Subject: Re: [PATCH v5] clk: tegra: Initialize UTMIPLL when enabling PLLU

On Thu, Jun 30, 2016 at 11:32:14AM -0400, Rhyland Klein wrote:
> On 6/17/2016 11:23 AM, Thierry Reding wrote:
> > * PGP Signed by an unknown key
> > 
> > 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@...omium.org>
> >>>
> >>> 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@...omium.org>
> >>>
> >>> [rklein: Merged in some later fixes for potential deadlocks]
> >>>
> >>> Signed-off-by: Rhyland Klein <rklein@...dia.com>
> >>> ---
> >>> 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?
> > 
> 
> It looks like we should be able to use a short udelay of 1-2us. I
> believe the original code had udelay(1) and I know Jon and I tested
> udelay(2) and it was ok.

What original code? The downstream driver? If so I'd be leaning towards
simply adopting that. Everything else in this functions seems to want to
wait for 1 us, seems natural for this to do as well.

> Do you want me to send another patch rev with just the udelay change or
> are you going to just modify it locally yourself?

No need to resend, I'll cherry-pick the patch from next-20160617 and
make this into udelay(1).

Thierry

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