• Arindam Nath's avatar
    mmc: sd: add support for signal voltage switch procedure · f2119df6
    Arindam Nath authored
    Host Controller v3.00 adds another Capabilities register. Apart
    from other things, this new register indicates whether the Host
    Controller supports SDR50, SDR104, and DDR50 UHS-I modes. The spec
    doesn't mention about explicit support for SDR12 and SDR25 UHS-I
    modes, so the Host Controller v3.00 should support them by default.
    Also if the controller supports SDR104 mode, it will also support
    SDR50 mode as well. So depending on the host support, we set the
    corresponding MMC_CAP_* flags. One more new register. Host Control2
    is added in v3.00, which is used during Signal Voltage Switch
    procedure described below.
    
    Since as per v3.00 spec, UHS-I supported hosts should set S18R
    to 1, we set S18R (bit 24) of OCR before sending ACMD41. We also
    need to set XPC (bit 28) of OCR in case the host can supply >150mA.
    This support is indicated by the Maximum Current Capabilities
    register of the Host Controller.
    
    If the response of ACMD41 has both CCS and S18A set, we start the
    signal voltage switch procedure, which if successfull, will switch
    the card from 3.3V signalling to 1.8V signalling. Signal voltage
    switch procedure adds support for a new command CMD11 in the
    Physical Layer Spec v3.01. As part of this procedure, we need to
    set 1.8V Signalling Enable (bit 3) of Host Control2 register, which
    if remains set after 5ms, means the switch to 1.8V signalling is
    successfull. Otherwise, we clear bit 24 of OCR and retry the
    initialization sequence. When we remove the card, and insert the
    same or another card, we need to make sure that we start with 3.3V
    signalling voltage. So we call mmc_set_signal_voltage() with
    MMC_SIGNAL_VOLTAGE_330 set so that we are back to 3.3V signalling
    voltage before we actually start initializing the card.
    
    Tested by Zhangfei Gao with a Toshiba uhs card and general hs card,
    on mmp2 in SDMA mode.
    Signed-off-by: default avatarArindam Nath <arindam.nath@amd.com>
    Reviewed-by: default avatarPhilip Rakity <prakity@marvell.com>
    Tested-by: default avatarPhilip Rakity <prakity@marvell.com>
    Acked-by: default avatarZhangfei Gao <zhangfei.gao@marvell.com>
    Signed-off-by: default avatarChris Ball <cjb@laptop.org>
    f2119df6
sdhci.h 9.89 KB