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SDHCI(4)              DragonFly Kernel Interfaces Manual              SDHCI(4)


NAME

     sdhci - PCI SD Host Controller bridge driver


SYNOPSIS

     To compile this driver into the kernel, place the following lines in your
     kernel configuration file:

           device mmc
           device mmcsd
           device sdhci

     Alternatively, to load the driver as a module at boot time, place the
     following lines in loader.conf(5):

           mmc_load="YES"
           mmcsd_load="YES"
           sdhci_pci_load="YES"
           sdhci_acpi_load="YES"


DESCRIPTION

     The sdhci driver supports PCI devices with class 8 and subclass 5
     according to SD Host Controller Specification, as well as various
     controllers discovered via ACPI.  Driver supports up to six slots per
     controller for either 1 or 4bit SD cards, or 1, 4 or 8bit MMC/eMMC slots
     per controller.  Supports up to 50MHz HighSpeed transfer speed on SD and
     MMC/eMMC cards, as well as DDR52 transfer mode on eMMC.  Driver attaches
     mmc bus to the respective slot on card insertion and detaches it on card
     removing.


HARDWARE

     The sdhci driver supports different specification compatible chips. The
     following chips have been verified to work:

     *   ENE CB712
     *   ENE CB714
     *   RICOH R5C822
     *   RICOH R5CE823
     *   TI PCIXX21/XX11
     *   Intel Bay-/Cherry-Trail eMMC and SDXC card reader
     *   AMDI0040 eMMC controller (AMD Zen+ SoC)
     *   O2 Micro OZ620 SD/MMC card reader
     *   O2 Micro OZ777 SD/MMC card reader


LOADER TUNABLES

     hw.sdhci.debug
             Set verbose debugging level.  Levels 0 to 3 are currently used.

     hw.sdhci.adma2_test
             Set to 1 to allow using ADMA2 transfer mode on untested
             controller models.

     hw.sdhci.sdma_disable
             Set to 1 to disable the SDMA transfer mode.

     hw.sdhci.adma2_disable
             Set to 1 to disable the ADMA2 transfer mode.

     hw.sdhci.quirk_clear
             Set bit mask of quirks to clear.

     hw.sdhci.quirk_set
             Set bit mask of quirks to set, this is applied after the clearing
             mask.

     hw.sdhci_enable_msi
             Set to 0 to disable MSI interrupt use.


SYSCTL VARIABLES

     hw.sdhci.debug
             Set verbose debugging level.

     dev.sdhci_acpi.X.timeout

     dev.sdhci_pci.X.timeout
             Maximum timeout for SDHCI transfers (in secs).


SEE ALSO

     mmc(4), mmcsd(4)

     SD Specifications, Part 2, SD Host Controller, Simplified Specification.


HISTORY

     The sdhci driver was imported from FreeBSD into DragonFly 2.7 and updated
     by Markus Pfeiffer <profmakx@dragonflybsd.org>.


AUTHORS

     Alexander Motin <mav@FreeBSD.org>


BUGS

     Many of existing SD controller chips have some nonstandard requirements,
     proprietary registers and hardware bugs, requiring additional handling.
     ENE chips are handled to work fine, while some revisions of RICOH and TI
     controllers still do not see cards without some additional
     initialization.

DragonFly 6.5-DEVELOPMENT        May 13, 2026        DragonFly 6.5-DEVELOPMENT

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