What is a GPIO?¶
General Purpose IO (GPIO) is a digital signal pin and can be configured to be either an input or an output signal. GPIO pins offer flexibility to platform designers and can be used for a variety of purposes. For example, a laptop lid may be connected to a gpio pin to signal when the lid is closed and can be used to turn on/off the display. Another example of a GPIO is to drive a status LED on the chassis. A very good primer on GPIO can be found here - https://www.kernel.org/doc/html/latest/driver-api/gpio/intro.html#what-is-a-gpio.
Modern chipsets pack multiple functions and are often constrained by the package size and limited number of pins. These Configurable IO pins need to be configured at boot time to connect them to selected functionality based on platform designs.
SBL provides a user friendly interface to ease configuration of GPIO/CFIO through its configuration infrastructure and this section provides an overview of the configuration steps.
GPIO config data¶
Step1. In the console launch the “ConfigEditor” from “slimbootloader” folder.
ConfigEditor is run using ConfigEditor.py script:
Step2. Open the “Config DSC” file, then select the description file according to your platform( eg. /Platform/CoffeelakeBoardPkg/CfgData/CfgDataDef.dsc”)
Step 3. Load the “Config Delta” file from the same folder of the description file by selecting “Load Config Changes from Delta File” menu.
Step 4. At the menu panel in left, select the “GPIO Settings”, and Select GPIO number which needs to be updated.
Refer to https://slimbootloader.github.io/tools/index.html#cfgtool for description regarding these pins .
- GPIO pins are grouped into different Community (e.g. Community 0, Community 1,etc.). Each Community consists of one or more GPIO groups. Refer to Corresponding EDS document for more details.
Step 5. Save the changes with “save config changes to Delta File” to the required board specific dlt file
Changes shall be reflected into the dlt file. Open the corresponding dlt file in notepad and check if the value is updated accordingly.
Step 6. Now build the SBL and flash it. SBL will apply the new settings on subsequent boots.
For SBL build process, Please refer https://slimbootloader.github.io/getting-started/build-source.html
GenGpioData.py is a utility that converts the GPIO pin data from one format to other. When starting a new project, often times the GPIO information for that platform is available in a format that needs to be converted to dsc/dlt to be used in SBL. For example, the GPIO information for a platform may have to be retrieved from the chipset data sheet or from the CRB BIOS..
Run GenGpioData Tool¶
GenGpioData Tool is run using GenGpioData.py script:
python GenGpioData.py <option 1> <option 2> <option 3> option 1 : GPIO input data file option 2 : Output SBL format option 3 : output path Example: Python GenGpioData.py -if GpioTableXxx.h -of dsc -o .
Input is .h and output is .dsc:
python GenGpioData.py -if GpioTableXxx.h -of dsc -o .
Input is .h and output is .dlt:
python GenGpioData.py -if GpioTableXxx.h -of dlt -o .
Input is .csv and output is .dsc:
python GenGpioData.py -if GpioTablexx.csv -of dsc -o .
Input is .csv and output is .dlt:
python GenGpioData.py -if GpioTablexx.csv -of dlt -o .
Refer to https://slimbootloader.github.io/tools/index.html#cfgtool for description regarding GPIO tool supported formats .
GpioTablexxx.h file shall be imported from BIOS source. Depending upon requirement this table can be updated.
Example :Input format is .h and output generated is .dsc file
Using Config editor the generated Dsc file can be loaded and modified
Generated Dsc file looks like