On 23/07/19 3:34 PM, Alan Cooper wrote: > On Tue, Jul 23, 2019 at 1:21 AM Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote: >> >> On 23/07/19 1:31 AM, Alan Cooper wrote: >>> I'm having a problem with a new SD/MMC controller and PHY in our >>> latest SoC's. The issue I'm seeing is that I can't switch into HS400 >>> mode. This looks like something the driver is doing that doesn't meet >>> the JEDEC spec. In the "HS400 timing mode selection" section of the >>> JEDEC spec , in step 7 it states: >>> >>> 7) Set the “Timing Interface” parameter in the HS_TIMING [185] field >>> of the Extended CSD register to 0x1 to switch to High Speed mode and >>> then set the clock frequency to a value not greater than 52 MHz. >>> >>> In the function mmc_select_hs400() in mmc.c, I see that a switch >>> command is done to set the eMMC device to HS mode and then >>> mmc_set_timing(card->host, MMC_TIMING_MMC_HS) is used to change the >>> controller to HS mode. The problem is that the "SD Host Controller >>> Standard Specification" states that "UHS Mode Select" field of the >>> "Host Control 2 Register" controls the mode when the "1.8V Signaling >>> Enable" bit in the same register is set, so mmc_set_timing() is >>> actually leaving the controller in SDR12 mode and mmc_select_hs400() >>> will then set the clock to 52MHz. This causes our PHY to detect an >>> illegal combination and return an error. >>> >>> I think the easiest fix would be to change mmc_set_timing(card->host, >>> MMC_TIMING_MMC_HS) to mmc_set_timing(card->host, >>> MMC_TIMING_UHS_SDR25). The other possibility would be to change >>> mmc_set_timing to handle the "1.8V Signaling Enable" bit properly. >>> I'll submit a patch based on the feedback I get. >> >> eMMC is governed by JEDEC specs not SD specs. > > My understanding is that JEDEC does not have a host controller spec so > this driver uses the "SD Host Controller Standard Specification". There is no spec for using eMMC with SDHCI. > >> >> Please consider making a change in your driver instead. For example, hook >> ->set_ios() and if 1.8V is enabled and timing is set to MMC_TIMING_MMC_HS >> then change it to MMC_TIMING_UHS_SDR25. > > That's an easy fix, but it still leaves all other drivers/systems > temporarily using SDR12 at 52MHz during the switch to HS400. Yes, I changed my mind. Does this work: diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c index 59acf8e3331e..f9d241458dcd 100644 --- a/drivers/mmc/host/sdhci.c +++ b/drivers/mmc/host/sdhci.c @@ -1849,7 +1849,9 @@ void sdhci_set_uhs_signaling(struct sdhci_host *host, unsigned timing) ctrl_2 |= SDHCI_CTRL_UHS_SDR104; else if (timing == MMC_TIMING_UHS_SDR12) ctrl_2 |= SDHCI_CTRL_UHS_SDR12; - else if (timing == MMC_TIMING_UHS_SDR25) + else if (timing == MMC_TIMING_SD_HS || + timing == MMC_TIMING_MMC_HS || + timing == MMC_TIMING_UHS_SDR25) ctrl_2 |= SDHCI_CTRL_UHS_SDR25; else if (timing == MMC_TIMING_UHS_SDR50) ctrl_2 |= SDHCI_CTRL_UHS_SDR50;
