Hi Nishanth
On 30/07/23 02:15, Nishanth Menon wrote:
From: Jason Kacines j-kacines@ti.com
Bootloader debug usually tends to be a bit dicey prior to DDR and serial port getting active in the system. JTAG typically remains the only practical debug option during the initial bringup.
OpenOCD is one of the most popular environment for providing debug capability via a gdb compatible interface for developers to work with.
Debugging U-boot and bootloaders on K3 platform does have a bit of tribal knowledge that is better documented in our common platform documentation.
Signed-off-by: Jason Kacines j-kacines@ti.com Signed-off-by: Nishanth Menon nm@ti.com
[...]
+* Board or the jtag adapter is supported: In most cases, board support
- is a relatively easy problem to solve if the board has a jtag pin header.
- All you need to do is ensure that the adapter you select is compatible
- with OpenOCD. Some boards do come with onboard JTAG adapter that just
- needs a USB cable to be plugged into the board, in which case, it is
- important to ensure that the jtag adapter is supported. Fortunately,
- almost all TI K3 SK/EVMs come with TI's xds110 which is supported out
s/xds110/XDS110
- of box with OpenOCD. The board specific documentation will cover the
- details and any adapter recommendations.
+.. code-block:: bash
- openocd -v
[...]
+**cTI20 connector**: The TI's `cTI20 +https://software-dl.ti.com/ccs/esd/documents/xdsdebugprobes/emu_jtag_connectors.html#cti-20-pin-header-information`_ connector +is probably the most prevelant on TI platforms. Though many +TI boards do have onboard xds110, cTI20 connector is usually
s/xds110/XDS110
+provided as an alternate scheme to connect alternatives such +as `Lauterbach https://www.lauterbach.com/`_ or `xds560
s/xds560/XDS560
+https://www.ti.com/tool/TMDSEMU560V2STM-U`_.
+To debug on these boards, the following combinations is suggested:
- or equivalent supported by OpenOCD
+* Cable such as `Tag-connect ribbon cable https://www.tag-connect.com/product/20-pin-cortex-ribbon-cable-4-length-with-50-mil-connectors`_ +* Adapter to convert cTI20 to ARM20 such as those from
- `Segger https://www.segger.com/products/debug-probes/j-link/accessories/adapters/ti-cti-20-adapter/`_
- `Lauterbach LA-3780 https://www.lauterbach.com/ad3780.html`_
- Or optionally, if you have manufacturing capability then you could try
- `beagle bone jtag adapter https://github.com/mmorawiec/BeagleBone-Black-JTAG-Adapters`_
s/beagle bone jtag adapter/BeagleBone JTAG Adapter
+.. warning::
- XDS560 and Lauterbach are proprietary solutions and is not supported by
- OpenOCD.
- When purchasing off the shelf adapters, you do want to be careful about the
- signalling though. Please `read for additional info https://software-dl.ti.com/ccs/esd/xdsdebugprobes/emu_jtag_connectors.html`_
+.. k3_rst_include_end_openocd_connect_cti20
+.. k3_rst_include_start_openocd_connect_tag_connect
+**Tag-Connect**: `Tag-Connect https://www.tag-connect.com/`_ +pads on the boards which require special cable. Please check the documentation +to `identify https://www.tag-connect.com/info/legs-or-no-legs`_ if "legged" +or "no-leg" version of the cable is appropriate for the board.
+To debug on these boards, you will need:
- or equivalent supported by OpenOCD
+* Tag-Connect cable appropriate to the board such as
s/tc2050-idc-nl/TC2050-IDC-NL
There's few more instances of these below as well.
+* In case of no-leg, version, a
- `retaining clip https://www.tag-connect.com/product/tc2050-clip-3pack-retaining-clip`_
+* Tag-Connect to ARM20
+.. note::
- You can optionally use a 3d printed solution such as
- `Protective cap https://www.thingiverse.com/thing:3025584`_ or
- `clip https://www.thingiverse.com/thing:3035278`_ to replace
- the retaining clip.
+.. warning::
- With the Tag-Connect to ARM20 adapter, Please solder the "Trst" signal for
- connection to work.
+.. k3_rst_include_end_openocd_connect_tag_connect
+Debugging with OpenOCD +^^^^^^^^^^^^^^^^^^^^^^
+Debugging U-boot is different from debugging regular user space +applications. The bootloader initialization process involves many boot +media and hardware configuration operations. For K3 devices, there +are also interactions with security firmware. While reloading the +"elf" file works through gdb, developers must be mindful of cascading +initialization's potential consequences.
+Consider the following code change:
+.. code-block:: diff
- --- a/file.c 2023-07-29 10:55:29.647928811 -0500
- +++ b/file.c 2023-07-29 10:55:46.091856816 -0500
- @@ -1,3 +1,3 @@
- val = readl(reg);
- -val |= 0x2;
- +val |= 0x1;
- writel(val, reg);
+Re-running the elf file with the above change will result in the +register setting 0x3 instead of the intended 0x1. There are other +hardware blocks which may not behave very well with re-initialization +sequence without proper shutdown.
+To help narrow the debug down, it is usually more simpler to use the +standard boot media to get to the booloader and debug only in the area
s/booloader/bootloader
+of interest.
+In general, to debug u-boot spl/u-boot with OpenOCD there are three steps:
[...]
+Connecting with OpenOCD for debug session +"""""""""""""""""""""""""""""""""""""""""
+Startup openocd to debug the platform as follows:
+* **integrated jtag interface**: If the evm has a debugger such as
s/integrated/Integrated
- xds110 inbuilt, there is typically an evm board support added and a
- cfg file will be available.
[...]
+At the time of this writing openOCD does not support tracing for K3 +platforms. Tracing function could be very useful if the bug in code +occurs deep within nested function and can optionally save developers +major trouble of stepping through large quantity of code.
But overall this patch is looking extremely helpful! Thanks!