Hi Jason,
On Tue, Oct 11, 2011 at 6:00 PM, Jason u-boot@lakedaemon.net wrote:
Simon, Stephen,
On Tue, Oct 11, 2011 at 04:54:27PM -0700, Simon Glass wrote:
Hi Stephen,
On Tue, Oct 11, 2011 at 4:37 PM, Stephen Warren swarren@nvidia.com wrote:
Simon Glass wrote at Tuesday, October 11, 2011 4:26 PM: ...
and add some defines to your board (only ARM is currently supported):
#define CONFIG_OF_CONTROL (to enable run-time config control via fdt) #define CONFIG_OF_EMBED or CONFIG_OF_SEPARATE (either build the fdt blob into U-Boot, or create a separate u-boot.dtb and u-boot-dtb.bin) #define CONFIG_DEFAULT_DEVICE_TREE "<your name>" (to specify the name of the device tree file is board/<vendor>/dts/<your name>.dts)
Typically a CPU device tree include file is provided which defines all the devices available on that CPU/SOC, with each set to 'status = "disabled"'. Board device tree files should adjust only the devices they use, setting 'status = 'ok"' in each case, and leaving the existing devices alone and disabled.
...
In the Linux kernel, things used to work exactly as described above, but the kernel has switched to having no "status" properties in the SoC base file (and hence everything defaults to enabled), with the per-board .dts files set 'status = "disabled"' where desired. I imagine U-Boot should follow the same practice.
I forget the exact reason for this in the kernel; it may simply have been due to precedent on PowerPC. Grant Likely would know the details.
Well it's going to create a bit of work for boards that use only a subset of these 30-peripheral SOCs, but perhaps the expectation is that you would be buying a simpler SOC if you didn't need all the features.
I imagine u-boot's methodology of loading drivers only as needed will prevent the unnecessary initialization of 30 drivers which are default 'status = "enabled";'. Or, am I missing something?
The glorious U-Boot driver refactor of 2015? :-) For now I don't know how this will turn out, and I will change the commit message in the next patch set.
Regards, Simon
thx,
Jason.