On 2 July 2012 16:50, Marc Dietrich <marvin24@xxxxxx> wrote: > Am Montag, 2. Juli 2012, 14:28:37 schrieb Girish K S: >> On 2 July 2012 14:23, Girish K S <girish.shivananjappa@xxxxxxxxxx> wrote: >> > On 2 July 2012 14:13, Saugata Das <saugata.das@xxxxxxxxxx> wrote: >> >> On 2 July 2012 12:26, Venkatraman S <svenkatr@xxxxxx> wrote: >> >>> This reverts commit 3d93576e(skip card initialization if >> >>> power class selection fails). >> >>> Problem has been reported when this is used with eMMC4.41 >> >>> card with Tegra Platform. Till the issue is root caused, >> >>> bus width selection failure should not be treated as fatal. >> >> >> >> According to me, we need to find the root issue (which could be either >> >> host not able to provide enough current or faulty eMMC). Do we know, >> >> what could be the side effect of working on eMMC with less power than >> >> what it has requested in PWR_CL ? >> >> >> >> One known issue with the current power class selection is that we do >> >> not check the current requirement for a selected power class. It >> >> assumes that host is able to provide the maximum current needed at >> >> highest speed (> 800mA). Is it already checked on Tegra ? >> > >> > and at the least bus width i.e 1 bit mode. >> >> The MMC card spec has 2 max current values (power class) one for 4 bit >> mode and another for 8 bit mode at supported voltages. But the SDHCI >> spec has one MaxCur register for supported voltages but doesnt mention >> for which bus width. Any input on this is very helpful to resolve the >> powerclass issue that is pending > > the higher nibble is for 8 bit and the lower one for 4 bit. The power class is > same for both bus width on this toshiba device. This is true from device point of view. but my concern was with the host controller register of SDHCI Spec MAXCURRn where n is 1.8 / 3.3 /3.0. Each voltage supported is assigned 8 bits (values ranging from 0-255). which means there is no split in nibbles for 4-bit and 8-bit mode > > Marc > -- 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
