On 9/16/25 08:02, Jan Kiszka wrote:
On 15.09.25 19:37, Cédric Le Goater wrote:
On 9/14/25 14:46, Jan Kiszka wrote:
From: Jan Kiszka <[email protected]>
Signed-off-by: Jan Kiszka <[email protected]>
Reviewed-by: Alex Bennée <[email protected]>
---
docs/system/device-emulation.rst | 1 +
docs/system/devices/emmc.rst | 52 ++++++++++++++++++++++++++++++++
2 files changed, 53 insertions(+)
create mode 100644 docs/system/devices/emmc.rst
diff --git a/docs/system/device-emulation.rst b/docs/system/device-
emulation.rst
index 911381643f..36429b1d17 100644
--- a/docs/system/device-emulation.rst
+++ b/docs/system/device-emulation.rst
@@ -101,3 +101,4 @@ Emulated Devices
devices/canokey.rst
devices/usb-u2f.rst
devices/igb.rst
+ devices/emmc.rst
diff --git a/docs/system/devices/emmc.rst b/docs/system/devices/emmc.rst
new file mode 100644
index 0000000000..dbea6d6c7e
--- /dev/null
+++ b/docs/system/devices/emmc.rst
@@ -0,0 +1,52 @@
+==============
+eMMC Emulation
+==============
+
+Besides SD card emulation, QEMU also offers an eMMC model as found on
many
+embedded boards. An eMMC, just like an SD card, is connected to the
machine
+via an SDHCI controller.
+
+Create eMMC Images
+==================
+
+A recent eMMC consists of 4 partitions: 2 boot partitions, 1 Replay
protected
+Memory Block (RPMB), and the user data area. QEMU expects backing
images for
+the eMMC to contain those partitions concatenated in exactly that order.
+However, the boot partitions as well as the RPMB might be absent if
their sizes
+are configured to zero.
+
+The eMMC specification defines alignment constraints for the
partitions. The
+two boot partitions must be of the same size. Furthermore, boot and RPMB
+partitions must be multiples of 128 KB with a maximum of 32640 KB for
each
+boot partition and 16384K for the RPMB partition.
+
+The alignment constrain of the user data area depends on its size. Up
to 2
+GByte, the size must be a power of 2. From 2 GByte onward, the size
has to be
+multiples of 512 byte.
+
+QEMU is enforcing those alignment rules before instantiating the device.
+Therefore, the provided image has to strictly follow them as well.
The helper
+script `scripts/mkemmc.sh` can be used to create compliant images,
with or
the single backquote would interpret scripts/mkemmc.sh as a ref. I think
you want ``scripts/mkemmc.sh``
+without pre-filled partitions. E.g., to create an eMMC image from a
firmware
+image and an OS image with an empty 2 MByte RPMB, use the following
command:
+
+.. code-block:: console
+
+ scripts/mkemmc.sh -b firmware.img -r /dev/zero:2MB os.img emmc.img
+
+This will take care of rounding up the partition sizes to the next
valid value
+and will leave the RPMB and the second boot partition empty (zeroed).
+
+Adding eMMC Devices
+===================
+
+An eMMC is either automatically created by a machine model (e.g.
Aspeed boards)
+or can be user-created when using a PCI-attached SDHCI controller. To
+instantiate the eMMC image from the example above while assuming that
the
+firmware needs a boot partitions of 1 MB, use the following options:
+
+.. code-block:: console
+
+ -drive file=emmc.img,if=none,format=raw,id=emmc-img
+ -device sdhci-pci
+ -device emmc,drive=emmc-img,boot-partition-size=1048576,rpmb-
partition-size=2097152
I will see if I can adjust the existing aspeed test with your proposal.
Thanks in advance! Yeah, the existing alignment rules were incorrect
once you turned on boot partitions. So there is unfortunately no way
around fixing images that followed them.
Ideally we should generate the rainier emmc image with your script
from the OpenBMC artifacts [1]. The current image is not broken by
this series, so, we have time.
However, regarding this command line :
-drive file=emmc.img,if=none,format=raw,id=emmc-img
-device sdhci-pci
-device emmc,drive=emmc-img,boot-partition-size=1048576,rpmb-size=2097152
a few assumptions are made.
Machines can have multiple sdhci controllers with several slots. In
the, case above, the emmc device is "blindly" attached to slot 0 on
a bus named "sd-bus".
Removing all QEMU internal references to "sd-bus" will require some work.
Philippe,
Should we allow automatic bus numbering :
- qbus_init(&s->sdbus, sizeof(s->sdbus), TYPE_SDHCI_BUS, DEVICE(s),
"sd-bus");
+ qbus_init(&s->sdbus, sizeof(s->sdbus), TYPE_SDHCI_BUS, DEVICE(s), NULL);
and replace all :
- BusState *bus = qdev_get_child_bus(DEVICE(sdhci), "sd-bus");
+ BusState *bus = BUS(&sdhci->sdbus);
Thanks,
C.
[1]
https://jenkins.openbmc.org/job/ci-openbmc/distro=ubuntu,label=docker-builder,target=p10bmc/32112/artifact/openbmc/build/tmp/deploy/images/p10bmc/
