Messages in this thread | | | Date | Thu, 20 Jun 2013 10:52:09 +0900 | From | Jaehoon Chung <> | Subject | Re: [PATCH v2 2/2] mmc: dw_mmc: Add the ability to set the ciu clock frequency |
| |
Hi Doug,
I'm researching for fixed-rate-clocks. Maybe i misunderstood for using <fixed-rate-clocks>. :)
Best Regards, Jaehoon Chung
On 06/19/2013 12:15 AM, Doug Anderson wrote: > Jaehoon, > > On Mon, Jun 17, 2013 at 9:51 PM, Jaehoon Chung <jh80.chung@samsung.com> wrote: >> Hi Doug, >> >> I have one question for using <clock-frequency>. >> I found the fixed-rate-clocks feature. >> If we want to set <clock-frequency>, then can we use the fixed-rate-clocks? >> i'm not sure how use the fixed-rate-clocks. but it seems to set fixed-rate value for clock frequency. >> >> clk_set_rate() didn't ensure to set the <clock-frequency> value. > > I'm not sure I understand the question. I don't think that the > fixed-rate-clocks have a close relation to the clock-frequency or the > ciu clock. The fixed-rate-clock entries for a board usually specify > the root clock source for a board. For instance in exynos5250-snow > you can see: > > fixed-rate-clocks { > xxti { > compatible = "samsung,clock-xxti"; > clock-frequency = <24000000>; > }; > }; > > Other clocks in the board are derived from this clock through PLLs, > muxes, dividers, gates, etc. On 5250 we have: > > fin_pll (xxti) -> fout_mpll -> fout_mplldiv2 -> mout_mpll_fout -> > sclk_mpll -> sclk_mpll_user -> mout_mmc1 -> div_mmc1 > div_mmc_pre1 -> sclk_mmc1 > > In 5250 the ciu clock for mmc1 is sclk_mmc1, which is a simple gate. > When you "enable" this clock it, ungates it. The sclk_mmc1 has the > flag CLK_SET_RATE_PARENT on it. That means when you try to set the > rate it will involve the parent clock (div_mmc_pre1). The parent > clock also has CLK_SET_RATE_PARENT, so it can also involve div_mmc1. > I haven't dug through to see how the clock framework splits up divides > between div_mmc1 and div_mmc_pre1, but it's supposed to handle that. > > We don't allow clk_set_rate to percolate any higher (no > CLK_SET_RATE_PARENT at mout_mmc1). > > -Doug > -- > To unsubscribe from this list: send the line "unsubscribe linux-mmc" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >
| |