linux-kernel - Re: [PATCH v2 19/19] clk: tegra210: add support for Tegra210 clocks

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Message-ID: <CAL1qeaHdjb57D8U-NBeyicV=JP2pNkyx3Xfn2RDgWivdw5jWNg@mail.gmail.com>
Date:	Thu, 30 Apr 2015 13:43:27 -0700
From:	Andrew Bresticker <abrestic@...omium.org>
To:	Rhyland Klein <rklein@...dia.com>
Cc:	Peter De Schrijver <pdeschrijver@...dia.com>,
	Mike Turquette <mturquette@...aro.org>,
	Stephen Warren <swarren@...dotorg.org>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Alexandre Courbot <gnurou@...il.com>,
	linux-clk@...r.kernel.org,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 19/19] clk: tegra210: add support for Tegra210 clocks

Hi Rhyland,

On Wed, Apr 29, 2015 at 10:21 AM, Rhyland Klein <rklein@...dia.com> wrote:
> Implement clock support for Tegra210.
>
> Signed-off-by: Rhyland Klein <rklein@...dia.com>

> --- /dev/null
> +++ b/drivers/clk/tegra/clk-tegra210.c

> +       /* PLLU */
> +       val = readl(clk_base + pll_u_params.base_reg);
> +       val &= ~BIT(24); /* disable PLLU_OVERRIDE */
> +       writel(val, clk_base + pll_u_params.base_reg);
> +
> +       clk = tegra_clk_register_pll("pll_u", "pll_ref", clk_base, pmc, 0,
> +                           &pll_u_params, &pll_u_lock);
> +       clk_register_clkdev(clk, "pll_u", NULL);
> +       clks[TEGRA210_CLK_PLL_U] = clk;
> +
> +       tegra210_utmi_param_configure(clk_base);
> +
> +       /* PLLU_480M */
> +       clk = clk_register_gate(NULL, "pll_u_480M", "pll_u",
> +                               CLK_SET_RATE_PARENT, clk_base + PLLU_BASE,
> +                               22, 0, &pll_u_lock);
> +       clk_register_clkdev(clk, "pll_u_480M", NULL);
> +       clks[TEGRA210_CLK_PLL_U_480M] = clk;
> +
> +       /* PLLU_60M */
> +       clk = clk_register_fixed_factor(NULL, "pll_u_60M", "pll_u",
> +                                       CLK_SET_RATE_PARENT, 1, 8);
> +       clk_register_clkdev(clk, "pll_u_60M", NULL);
> +       clks[TEGRA210_CLK_PLL_U_60M] = clk;
> +
> +       /* PLLU_48M */
> +       clk = clk_register_fixed_factor(NULL, "pll_u_48M", "pll_u",
> +                                       CLK_SET_RATE_PARENT, 1, 10);
> +       clk_register_clkdev(clk, "pll_u_48M", NULL);
> +       clks[TEGRA210_CLK_PLL_U_48M] = clk;
> +
> +       /* PLLU_12M */
> +       clk = clk_register_fixed_factor(NULL, "pll_u_12M", "pll_u",
> +                                       CLK_SET_RATE_PARENT, 1, 40);
> +       clk_register_clkdev(clk, "pll_u_12M", NULL);
> +       clks[TEGRA210_CLK_PLL_U_12M] = clk;

The PLLU hierarchy isn't quite right here.  pll_u_480M is derived from
the VCO output of pll_u (480Mhz) rather than the final output
(240Mhz).  It also looks, from downstream kernels and from the "PLLU
Configuration Information" table in the TRM, that pll_u_48M and
pll_u_60M are derived from pll_u_out1 and pll_u_out2, respectively.  I
don't see any mention of a 12Mhz output (pll_u_12M) either.

So I think the PLLU clock tree looks something like this:

pll_u_vco (480Mhz)
    pll_u_480M (480Mhz - gated by PLLU_BASE[22])
    pll_u (240Mhz)
        pll_u_out1 (48Mhz - PLLU_OUTA[15:0])
            pll_u_48M (48Mhz - gated by PLLU_BASE[25])
        pll_u_out2 (60Mhz - PLLU_OUTA[31:16])
            pll_u_60M (60Mhz - gated by PLLU_BASE[23])

-Andrew
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