the default partition, eMMC v4.41 and later devices can additionally
provide up to:
1 enhanced user data area partition
2 boot partitions
1 RPMB (Replay Protected Memory Block) partition
4 general purpose partitions (optionally with a enhanced or extended
attribute)
Of these "partitions", only the enhanced user data area one actually
slices the user data area partition and, thus, gets handled with the
help of geom_flashmap(4). The other types of partitions have address
space independent from the default partition and need to be switched
to via CMD6 (SWITCH), i. e. constitute a set of additional "disks".
The second kind of these "partitions" doesn't fit that well into the
design of mmc(4) and mmcsd(4). I've decided to let mmcsd(4) hook all
of these "partitions" up as disk(9)'s (except for the RPMB partition
as it didn't seem to make much sense to be able to put a file-system
there and may require authentication; therefore, RPMB partitions are
solely accessible via the newly added IOCTL interface currently; see
also below). This approach for one resulted in cleaner code. Second,
it retains the notion of mmcsd(4) children corresponding to a single
physical device each. With the addition of some layering violations,
it also would have been possible for mmc(4) to add separate mmcsd(4)
instances with one disk each for all of these "partitions", however.
Still, both mmc(4) and mmcsd(4) share some common code now e. g. for
issuing CMD6, which has been factored out into mmc_subr.c.
Besides simply subdividing eMMC devices, some Intel NUCs having UEFI
code in the boot partitions etc., another use case for the partition
support is the activation of pseudo-SLC mode, which manufacturers of
eMMC chips typically associate with the enhanced user data area and/
or the enhanced attribute of general purpose partitions.
CAVEAT EMPTOR: Partitioning eMMC devices is a one-time operation.
- Now that properly issuing CMD6 is crucial (so data isn't written to
the wrong partition for example), make a step into the direction of
correctly handling the timeout for these commands in the MMC layer.
Also, do a SEND_STATUS when CMD6 is invoked with an R1B response as
recommended by relevant specifications. However, quite some work is
left to be done in this regard; all other R1B-type commands done by
the MMC layer also should be followed by a SEND_STATUS (CMD13), the
erase timeout calculations/handling as documented in specifications
are entirely ignored so far, the MMC layer doesn't provide timeouts
applicable up to the bridge drivers and at least sdhci(4) currently
is hardcoding 1 s as timeout for all command types unconditionally.
Let alone already available return codes often not being checked in
the MMC layer ...
- Add an IOCTL interface to mmcsd(4); this is sufficiently compatible
with Linux so that the GNU mmc-utils can be ported to and used with
FreeBSD (note that due to the remaining deficiencies outlined above
SANITIZE operations issued by/with `mmc` currently most likely will
fail). These latter will be added to ports as sysutils/mmc-utils in
a bit. Among others, the `mmc` tool of the GNU mmc-utils allows for
partitioning eMMC devices (tested working).
- For devices following the eMMC specification v4.41 or later, year 0
is 2013 rather than 1997; so correct this for assembling the device
ID string properly.
- Let mmcsd.ko depend on mmc.ko. Additionally, bump MMC_VERSION as at
least for some of the above a matching pair is required.
- In the ACPI front-end of sdhci(4) describe the Intel eMMC and SDXC
controllers as such in order to match the PCI one.
Additionally, in the entry for the 80860F14 SDXC controller remove
the eMMC-only SDHCI_QUIRK_INTEL_POWER_UP_RESET.
OKed by: imp
Submitted by: ian (mmc_switch_status() implementation)
