On Wed, Sep 25, 2019 at 10:58 PM Simon Glass <s...@chromium.org> wrote: > > Sometimes devices don't appear and it can be confusing. Add a few notes to > help with this situation. > > Signed-off-by: Simon Glass <s...@chromium.org> > --- > > doc/driver-model/debugging.rst | 62 ++++++++++++++++++++++++++++++++++
missed updating index.rst to include this doc. I can fix this when applying. > 1 file changed, 62 insertions(+) > create mode 100644 doc/driver-model/debugging.rst > > diff --git a/doc/driver-model/debugging.rst b/doc/driver-model/debugging.rst > new file mode 100644 > index 00000000000..9711dd6d653 > --- /dev/null > +++ b/doc/driver-model/debugging.rst > @@ -0,0 +1,62 @@ > +.. SPDX-License-Identifier: GPL-2.0+ > +.. sectionauthor:: Simon Glass <s...@chromium.org> > + > +Debugging driver model > +====================== > + > +This document aims to provide help when you cannot work out why driver model > is > +not doing what you expect. > + > + > +Useful techniques in general > +---------------------------- > + > +Here are some useful debugging features generally. > + > + - If you are writing a new feature, consider doing it in sandbox instead > of > + on your board. Sandbox has no limits, allows each debugging (e.g. gdb) > and easy debugging > + you can writing emulators for most common devices. write > + - Put '#define DEBUG' at the top of a file, to activate all the debug() > and > + log_debug() statements in that file. > + - Where logging is used, change the logging level, e.g. in SPL with > + CONFIG_SPL_LOG_MAX_LEVEL=7 (which is LOGL_DEBUG) and > + CONFIG_LOG_DEFAULT_LEVEL=7 > + - Where logging of return values is implemented with log_msg_ret(), set > + CONFIG_LOG_ERROR_RETURN=y to see exactly where the error is happening > + - Make sure you have a debug UART enabled - see CONFIG_DEBUG_UART. With > this > + you can get serial output (printf(), etc.) before the serial driver is > + running. > + - Use a JTAG emulator to set breakpoints and single-step through code > + > +Not that most of these increase code/data size somewhat when enabled. > + > + > +Failure to locate a device > +-------------------------- > + > +Let's say you have uclass_first_device_err() and it is not finding anything. > + > +If it is returning an error, then that gives you a clue. Look up > linux/errno.h > +to see errors. Common ones are: > + > + - -ENOMEM which indicates that memory is short. If it happens in SPL or > + before relocation in U-Boot, check CONFIG_SPL_SYS_MALLOC_F_LEN and > + CONFIG_SYS_MALLOC_F_LEN as they may need to be larger. Add '#define > DEBUG' > + at the very top of malloc_simple.c to get an idea of where your memory > is > + going. > + - -EINVAL which typically indicates that something was missing or wrong in > + the device tree node. Check that everything is correct and look at the > + ofdata_to_platdata() method in the driver. > + > +If there is no error, you should check if the device is actually bound. Call > +dm_dump_all() just before you locate the device to make sure it exists. > + > +If it does not exist, check your device tree compatible strings match up with > +what the driver expects (in the struct udevice_id array). > + > +If you are using of-platdata (e.g. CONFIG_SPL_OF_PLATDATA), check that the > +driver name is the same as the first compatible string in the device tree > (with > +invalid-variable characters converted to underscore). > + > +If you are really stuck, #define DEBUG at the top of lists.c should show you > +what is going on. > -- Other than that, Reviewed-by: Bin Meng <bmeng...@gmail.com> Tested-by: Bin Meng <bmeng...@gmail.com> _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot
