>>>>> + >>>>> + host->ciu_clk = clk_get(host->dev, "ciu"); >>>>> + if (IS_ERR(host->ciu_clk)) >>>>> + dev_dbg(host->dev, "ciu clock not available\n"); >>>>> + else >>>>> + clk_prepare_enable(host->ciu_clk); >>>>> + >>>>> + if (IS_ERR(host->ciu_clk)) >>>>> + host->bus_hz = host->pdata->bus_hz; >>>>> + else >>>>> + host->bus_hz = clk_get_rate(host->ciu_clk); >>>> if clk_get_rate() is incorrect value(ex,400MHz), >>>> then mmc->f_min value is too high. >>>> because mmc->f_min is assigned to DIV_ROUND_UP(host->bus_hz, 510) into dw_mc_init_slot. >>>> Do you have any opinion for solving this? >>> >>> One option on Exynos5250 is to use the clock divider in the CLKSEL >>> register to divide the ciu clock to a lower value. For Exynos4, since >>> there is no clock divider in CLKSEL register, the platform code should >>> ensure that the ciu clock has a valid range. >> I know that can use div-ratio filed at the clksel register. >> On Exynos5, i known that is used the div-ratio at CLKSEL register. >> If ciu-clock is 400MHz, host->bus_hz is assigned to 400MHz. >> 1) host->bus_hz -> 400MHz (at dw-mmc-pltfm.c) >> 2) mmc->f_min = DIV_ROUND_UP(host->bus_hz, 510) then mmc->f_min is set to 784KHz. >> 3) then host->bus_hz is re-assigned to value that is divided to div-ratio at CLKSEL register. >> at this time, host->bus_hz = 100MHz... >> >> I think this sequence is something wrong. >> (Is 784KHz too high for init card?) >> >> It's just my thinking..if my understanding is wrong, let me know plz. > > You have listed the steps 1 to 3 correctly. So, as per step 3, 100Mhz > / 510 ~= 196KHz. Which is well within 400KHz. So do you still see a > problem here? How do you think about this? [ 4.620000] mmc_host mmc0: Bus speed (slot 0) = 100000000Hz (slot req 784314Hz, actual 781250HZ div = 64) Best Regards, Jaehoon Chung > > Thanks, > Thomas. > -- > To unsubscribe from this list: send the line "unsubscribe linux-mmc" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
