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SubjectRe: [PATCH] clk: tegra: use pll_ref as the pll_e parent
On 10/29/2013 06:41 PM, Peter De Schrijver wrote:
> Use pll_ref instead of pll_re_vco as the pll_e parent on Tegra114 and
> Tegra124. Also add a pll_ref table entry for pll_e for Tegra114.

Why? What benefit does this give, or what bug does this fix?

> diff --git a/drivers/clk/tegra/clk-pll.c b/drivers/clk/tegra/clk-pll.c

> val_aux = pll_readl(pll_params->aux_reg, pll);
>
> if (val & PLL_BASE_ENABLE) {
> - if (!(val_aux & PLLE_AUX_PLLRE_SEL))
> + if ((val_aux & PLLE_AUX_PLLRE_SEL) || (val_aux & val_aux))

Isn't "|| (val_aux & val_aux)" always true, at least if the value is
non-zero? Either this should be simply "|| val_aux", or one of those two
"val_aux" is the wrong thing.

> WARN(1, "pll_e enabled with unsupported parent %s\n",
> - (val & PLLE_AUX_PLLP_SEL) ? "pllp_out0" : "pll_ref");
> + (val_aux & PLLE_AUX_PLLP_SEL) ? "pllp_out0" :
> + "pll_re_vco");
> } else {
> - val_aux |= PLLE_AUX_PLLRE_SEL;
> + val_aux &= ~(PLLE_AUX_PLLRE_SEL | PLLE_AUX_PLLP_SEL);
> pll_writel(val, pll_params->aux_reg, pll);
> }

> diff --git a/drivers/clk/tegra/clk-tegra114.c b/drivers/clk/tegra/clk-tegra114.c

> @@ -560,6 +560,7 @@ static struct tegra_clk_pll_freq_table pll_e_freq_table[] = {
> /* PLLE special case: use cpcon field to store cml divider value */
> {336000000, 100000000, 100, 21, 16, 11},
> {312000000, 100000000, 200, 26, 24, 13},
> + {12000000, 100000000, 200, 1, 24, 13},

Presumably this is because pll_ref is the crystal, which runs at 12MHz.
What if it doesn't; Tegra supports a bunch of other crystal rates. Don't
we need entries for all the other potential crystal rates too?


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