Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1201565

Re: [PATCH v6 7/9] clk: mediatek: Add subsystem clocks of MT8173

Show all headers | View raw

Hi Sascha,

On Wed, 2015-08-05 at 08:46 +0200, Sascha Hauer wrote:
> On Tue, Aug 04, 2015 at 04:16:56PM +0800, James Liao wrote:
> >  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),
> > +	FIXED_CLK(CLK_TOP_DSI0_DIG, "dsi0_dig", "clk26m", 130 * MHZ),
> > +	FIXED_CLK(CLK_TOP_DSI1_DIG, "dsi1_dig", "clk26m", 130 * MHZ),
> > +	FIXED_CLK(CLK_TOP_LVDS_PXL, "lvds_pxl", "lvdspll", 148.5 * MHZ),
> > +	FIXED_CLK(CLK_TOP_LVDS_CTS, "lvds_cts", "lvdspll", 51.975 * MHZ),
> 
> I would expect 51975 * KHZ here to avoid fractional numbers. Probably
> gcc calculates that during compile time so this will work as expected,
> still I'm not sure this is good style to use fractional numbers here.

As I know all constants will be calculated in compile time, so there
should be no difference between 51.975 * MHZ and 51975 * KHz. 

> Anyway, on my system lvdspll is running at 150MHz. Are you sure there is
> a clock derived from this running at 148.5MHz? Is it really correct to
> use a fixed clock here or should it rather be lvdspll directly?

Here is the clock hierarchy between lvdspll and lvds_pxl:

            --------       AD_VPLL_DPIX_CK  --------   lvds_pxl  -----
           |        |--------------------->|        |---------->|
           |        |                      | cksys  |           |
LVDSPLL -->| LVDSTX |                      | buffer |           | MMSYS
           |        | AD_LVDSTX_CLKDIG_CTS | test   |  lvds_cts |
           |        |--------------------->|        |---------->|
            --------                        --------             -----

Some clocks and blocks are not modeled into CCF. But we prefer to enable
lvdspll before enabling lvds_pxl. So I modeled lvds_pxl (and lvds_cts)
as a fixed-rate clock with a source from lvdspll.

The frequency of these fixed-rate clocks (such as 148.5 MHz) are typical
rate. In fact, we don't care about the actual rate of these clocks. We
just care about the enable / disable sequence of them.


Best regards,

James


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Re: [PATCH v6 7/9] clk: mediatek: Add subsystem clocks of MT8173 Sascha Hauer <s.hauer@pengutronix.de> - 2015-08-05 08:50 +0200
  Re: [PATCH v6 7/9] clk: mediatek: Add subsystem clocks of MT8173 Daniel Kurtz <djkurtz@chromium.org> - 2015-08-05 09:30 +0200
    Re: [PATCH v6 7/9] clk: mediatek: Add subsystem clocks of MT8173 Sascha Hauer <s.hauer@pengutronix.de> - 2015-08-05 09:40 +0200
      Re: [PATCH v6 7/9] clk: mediatek: Add subsystem clocks of MT8173 Daniel Kurtz <djkurtz@chromium.org> - 2015-08-05 09:50 +0200
        Re: [PATCH v6 7/9] clk: mediatek: Add subsystem clocks of MT8173 Sascha Hauer <s.hauer@pengutronix.de> - 2015-08-05 10:00 +0200
          Re: [PATCH v6 7/9] clk: mediatek: Add subsystem clocks of MT8173 Daniel Kurtz <djkurtz@chromium.org> - 2015-08-05 10:00 +0200
  Re: [PATCH v6 7/9] clk: mediatek: Add subsystem clocks of MT8173 James Liao <jamesjj.liao@mediatek.com> - 2015-08-06 10:30 +0200
    Re: [PATCH v6 7/9] clk: mediatek: Add subsystem clocks of MT8173 Sascha Hauer <s.hauer@pengutronix.de> - 2015-08-06 11:00 +0200
      Re: [PATCH v6 7/9] clk: mediatek: Add subsystem clocks of MT8173 James Liao <jamesjj.liao@mediatek.com> - 2015-08-06 11:10 +0200
        Re: [PATCH v6 7/9] clk: mediatek: Add subsystem clocks of MT8173 Daniel Kurtz <djkurtz@chromium.org> - 2015-08-06 11:20 +0200
          Re: [PATCH v6 7/9] clk: mediatek: Add subsystem clocks of MT8173 Sascha Hauer <s.hauer@pengutronix.de> - 2015-08-06 12:30 +0200
            Re: [PATCH v6 7/9] clk: mediatek: Add subsystem clocks of MT8173 James Liao <jamesjj.liao@mediatek.com> - 2015-08-07 04:30 +0200
              Re: [PATCH v6 7/9] clk: mediatek: Add subsystem clocks of MT8173 Daniel Kurtz <djkurtz@chromium.org> - 2015-08-07 10:10 +0200
                Re: [PATCH v6 7/9] clk: mediatek: Add subsystem clocks of MT8173 Daniel Kurtz <djkurtz@chromium.org> - 2015-08-07 10:10 +0200

csiph-web