Philip Rakity wrote: > On Jun 28, 2011, at 3:54 AM, Jaehoon Chung wrote: > >> Hi.. >> >> I found the MMC_CAP_BUS_WIDTH_TEST... >> In mailing, I read the related patches.. >> but i didn't fully understand... >> >> /* >> * If controller can't handle bus width test, >> * compare ext_csd previously read in 1 bit mode >> * against ext_csd at new bus width >> */ >> if (!(host->caps & MMC_CAP_BUS_WIDTH_TEST)) >> err = mmc_compare_ext_csds(card, >> ext_csd, >> bus_width); >> else >> err = mmc_bus_test(card, bus_width); >> if (!err) >> break; >> >> And i tested suspend/resume..it's failed.. >> If i didn't set MMC_CAP_BUS_WIDTH_TEST, always return -EINVAL.. >> (using SDHCI controller, card is eMMC4.41) >> >> Didn't compare ext_csd's value.. >> >> So i want to know how use MMC_CAP_BUS_WIDTH_TEST.. > > I am using eMMC and code works fine so maybe there is issue in no ext_csd. You will need to > add debug code to the compare_ext_csd and see what is not right and we can adjust the code. > I am surprised that resume fails -- code will default to 1 bit data and it is NOT possible for this to > be wrong. At the moment -- clueless to explain with more information. > > TheCMD14/ CMD19 is in JEDEC spec for bus width testing. Sends a pattern to the card and > based on the returned values detects the bus width. Some controllers do NOT support this command. > The just do not work. You need to figure this out by enabling the quirk. No other way to know. When card is probing, i think that need to test bus-width. If card is non-removable, unnecessary bus_width test during resuming. Because already know that support n-bit bus-width..how about this? > > regards, > > Philip > >> Thanks, >> Jaehoon Chung > > -- > 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
