Re: [PATCH v6 5/9] clk: mediatek: Fix rate and dependency of MT8173 clocks

[James Liao]

Hi Sascha,

On Wed, 2015-08-05 at 08:53 +0200, Sascha Hauer wrote:
> On Tue, Aug 04, 2015 at 04:16:54PM +0800, James Liao wrote:
> > -static const struct mtk_fixed_factor root_clk_alias[] __initconst = {
> > -	FACTOR(CLK_TOP_CLKPH_MCK_O, "clkph_mck_o", "clk_null", 1, 1),
> > -	FACTOR(CLK_TOP_USB_SYSPLL_125M, "usb_syspll_125m", "clk_null", 1, 1),
> > -	FACTOR(CLK_TOP_HDMITX_DIG_CTS, "hdmitx_dig_cts", "clk_null", 1, 1),
> > +static const struct mtk_fixed_clk fixed_clks[] __initconst = {
> > +	FIXED_CLK(CLK_TOP_CLKPH_MCK_O, "clkph_mck_o", "clk26m", 400 * MHZ),
> > +	FIXED_CLK(CLK_TOP_USB_SYSPLL_125M, "usb_syspll_125m", "clk26m", 125 * MHZ),
> 
> Hm, it seems you hide PLLs in fixed factor clock. Are you sure that
> there is a PLL in the system generating 125MHz from 26MHz which is in no
> way configurable? Or is this really some clock derived from the syspll
> as the clock name suggests?

According to the datasheet from our clock designer, usb_syspll_125m is
the output clock of an analog macro which is named SSUSB_PHY, and its
input clock is AD_CLK26M_CK.

SSUSB_PHY is not the same as general PLLs such as MAINPLL. So I don't
treat it as a configurable PLL but a fixed clock with the typical rate
125 MHz.


Best regards,

James

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