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

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Date:	Thu, 30 Apr 2015 16:57:30 -0400
From:	Rhyland Klein <rklein@...dia.com>
To:	Andrew Bresticker <abrestic@...omium.org>
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

On 4/30/2015 4:43 PM, Andrew Bresticker wrote:
> 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
> 

Thanks for pointing this out, I'll look into it for v3.

-rhyland

-- 
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