Build U-Boot sandbox and run it:
- make sandbox_config
+ make sandbox_defconfig
make
- ./u-boot
+ ./u-boot -d u-boot.dtb
(type 'reset' to exit U-Boot)
You should see something like this:
<...U-Boot banner...>
- Running 22 driver model tests
+ Running 29 driver model tests
Test: dm_test_autobind
Test: dm_test_autoprobe
Test: dm_test_bus_children
Device 'd-test': seq 3 is in use by 'b-test'
Device 'a-test': seq 0 is in use by 'd-test'
Test: dm_test_gpio
- sandbox_gpio: sb_gpio_get_value: error: offset 4 not reserved
+ extra-gpios: get_value: error: gpio b5 not reserved
+ Test: dm_test_gpio_anon
+ Test: dm_test_gpio_copy
+ Test: dm_test_gpio_leak
+ extra-gpios: get_value: error: gpio b5 not reserved
+ Test: dm_test_gpio_requestf
Test: dm_test_leak
Test: dm_test_lifecycle
Test: dm_test_operations
Test: dm_test_platdata
Test: dm_test_pre_reloc
Test: dm_test_remove
+ Test: dm_test_spi_find
+ Invalid chip select 0:0 (err=-19)
+ SF: Failed to get idcodes
+ Device 'name-emul': seq 0 is in use by 'name-emul'
+ SF: Detected M25P16 with page size 256 Bytes, erase size 64 KiB, total 2 MiB
+ Test: dm_test_spi_flash
+ 2097152 bytes written in 0 ms
+ SF: Detected M25P16 with page size 256 Bytes, erase size 64 KiB, total 2 MiB
+ SPI flash test:
+ 0 erase: 0 ticks, 65536000 KiB/s 524288.000 Mbps
+ 1 check: 0 ticks, 65536000 KiB/s 524288.000 Mbps
+ 2 write: 0 ticks, 65536000 KiB/s 524288.000 Mbps
+ 3 read: 0 ticks, 65536000 KiB/s 524288.000 Mbps
+ Test passed
+ 0 erase: 0 ticks, 65536000 KiB/s 524288.000 Mbps
+ 1 check: 0 ticks, 65536000 KiB/s 524288.000 Mbps
+ 2 write: 0 ticks, 65536000 KiB/s 524288.000 Mbps
+ 3 read: 0 ticks, 65536000 KiB/s 524288.000 Mbps
+ Test: dm_test_spi_xfer
+ SF: Detected M25P16 with page size 256 Bytes, erase size 64 KiB, total 2 MiB
Test: dm_test_uclass
Test: dm_test_uclass_before_ready
Failures: 0
in your ofdata_to_platdata (or probe) method to allocate the required memory,
and you should free it in the remove method.
+The driver model tree is intended to mirror that of the device tree. The
+root driver is at device tree offset 0 (the root node, '/'), and its
+children are the children of the root node.
+
Declaring Uclasses
------------------
U-Boot numbers devices from 0 in many situations, such as in the command
line for I2C and SPI buses, and the device names for serial ports (serial0,
serial1, ...). Driver model supports this numbering and permits devices
-to be locating by their 'sequence'. This numbering unique identifies a
+to be locating by their 'sequence'. This numbering uniquely identifies a
device in its uclass, so no two devices within a particular uclass can have
the same sequence number.
Sequence numbers start from 0 but gaps are permitted. For example, a board
-may have I2C buses 0, 1, 4, 5 but no 2 or 3. The choice of how devices are
+may have I2C buses 1, 4, 5 but no 0, 2 or 3. The choice of how devices are
numbered is up to a particular board, and may be set by the SoC in some
cases. While it might be tempting to automatically renumber the devices
where there are gaps in the sequence, this can lead to confusion and is
device will be automatically allocated the next available sequence number.
To specify the sequence number in the device tree an alias is typically
-used.
+used. Make sure that the uclass has the DM_UC_FLAG_SEQ_ALIAS flag set.
aliases {
serial2 = "/serial@22230000";
("/serial@22230000") will be given sequence number 2. Any command or driver
which requests serial device 2 will obtain this device.
-Some devices represent buses where the devices on the bus are numbered or
-addressed. For example, SPI typically numbers its slaves from 0, and I2C
-uses a 7-bit address. In these cases the 'reg' property of the subnode is
-used, for example:
-
-{
- aliases {
- spi2 = "/spi@22300000";
- };
-
- spi@22300000 {
- #address-cells = <1>;
- #size-cells = <1>;
- spi-flash@0 {
- reg = <0>;
- ...
- }
- eeprom@1 {
- reg = <1>;
- };
- };
-
-In this case we have a SPI bus with two slaves at 0 and 1. The SPI bus
-itself is numbered 2. So we might access the SPI flash with:
+More commonly you can use node references, which expand to the full path:
- sf probe 2:0
-
-and the eeprom with
-
- sspi 2:1 32 ef
-
-These commands simply need to look up the 2nd device in the SPI uclass to
-find the right SPI bus. Then, they look at the children of that bus for the
-right sequence number (0 or 1 in this case).
+aliases {
+ serial2 = &serial_2;
+};
+...
+serial_2: serial@22230000 {
+...
+};
-Typically the alias method is used for top-level nodes and the 'reg' method
-is used only for buses.
+The alias resolves to the same string in this case, but this version is
+easier to read.
Device sequence numbers are resolved when a device is probed. Before then
the sequence number is only a request which may or may not be honoured,
pointer is saved but not made available through the driver model API).
-Things to punt for later
-------------------------
+SPL Support
+-----------
+
+Driver model can operate in SPL. Its efficient implementation and small code
+size provide for a small overhead which is acceptable for all but the most
+constrained systems.
+
+To enable driver model in SPL, define CONFIG_SPL_DM. You might want to
+consider the following option also. See the main README for more details.
+
+ - CONFIG_SYS_MALLOC_SIMPLE
+ - CONFIG_DM_WARN
+ - CONFIG_DM_DEVICE_REMOVE
+ - CONFIG_DM_STDIO
-- SPL support - this will have to be present before many drivers can be
-converted, but it seems like we can add it once we are happy with the
-core implementation.
-That is not to say that no thinking has gone into this - in fact there
-is quite a lot there. However, getting these right is non-trivial and
-there is a high cost associated with going down the wrong path.
+Enabling Driver Model
+---------------------
-For SPL, it may be possible to fit in a simplified driver model with only
-bind and probe methods, to reduce size.
+Driver model is being brought into U-Boot gradually. As each subsystems gets
+support, a uclass is created and a CONFIG to enable use of driver model for
+that subsystem.
+
+For example CONFIG_DM_SERIAL enables driver model for serial. With that
+defined, the old serial support is not enabled, and your serial driver must
+conform to driver model. With that undefined, the old serial support is
+enabled and driver model is not available for serial. This means that when
+you convert a driver, you must either convert all its boards, or provide for
+the driver to be compiled both with and without driver model (generally this
+is not very hard).
+
+See the main README for full details of the available driver model CONFIG
+options.
+
+
+Things to punt for later
+------------------------
Uclasses are statically numbered at compile time. It would be possible to
change this to dynamic numbering, but then we would require some sort of
projects / u-boot / blobdiff