Modification of the README.md file

README.md

 # PetaLinux for Scalp board
 
-## Documentation to create a custom BSP for PetaLinux
+## Documentation to create a PetaLinux distribution for Scalp board
 
 PetaLinux is an extension of the Yocto project that provides official support (Xilinx layers) for Xilinx SoCs Arm (Zynq and ZynqMP) and Xilinx Microblaze.
 
@@ -182,8 +182,31 @@ The produced binary file can be found in the **./images/linux** folder. This is
 
 ### Flash firmware on QSPI memory
 
+If you are using a single JTAG probe.
+
+```
+$ program_flash -f images/linux/BOOT.BIN -offset 0 -flash_type qspi-x4-single -fsbl images/linux/zynq_fsbl.elf -cable type xilinx_tcf url TCP:127.0.0.1:3121
+```
+
+The **program_flash** command is located in the Vivado installation folder.
+
+If you use several JTAG probes.
+
 ```
-petalinux-package --boot --fsbl images/linux/zynq_fsbl.elf --fpga images/linux/system.bit --u-boot --kernel --offset 0x520000
+$ program_flash -jtagtarget
+
+JTAG chain configuration
+--------------------------------------------------
+1 Digilent 210299AFC175 
+	2    jsn-JTAG-HS3-210299AFC175-4ba00477-0  (name arm_dap  idcode 4ba00477)
+	3    jsn-JTAG-HS3-210299AFC175-0373b093-0  (name xc7z015  idcode 0373b093)
+4 Xilinx 00001a3719fe01 
+	5    jsn-DLC10-00001a3719fe01-4ba00477-0  (name arm_dap  idcode 4ba00477)
+	6    jsn-DLC10-00001a3719fe01-0373b093-0  (name xc7z015  idcode 0373b093)
+    
+$ program_flash -f images/linux/BOOT.BIN -offset 0 -flash_type qspi-x4-single -fsbl images/linux/zynq_fsbl.elf -target_id 2 -url TCP:127.0.0.1:3121
+
+$ program_flash -f images/linux/BOOT.BIN -offset 0 -flash_type qspi-x4-single -fsbl images/linux/zynq_fsbl.elf -target_id 5 -url TCP:127.0.0.1:3121
 ```
 
 The **image.ub** file corresponds to the image of the Linux kernel, the device tree and the RamFS file system in FIT format.
@@ -195,3 +218,45 @@ The image content can be viewed using the **dumpimage** command.
 ```
 
 In my case, I copied the tools produced by U-Boot into the **/tools/u-boot-tools/** folder.
+
+## HOWTO
+
+### Howto create a patch for U-Boot ?
+
+Retrieve the desired version of the U-Boot GIT deposit.
+
+```
+$ git clone https://github.com/Xilinx/u-boot-xlnx.git
+$ cd u-boot-xlnx
+$ git checkout xilinx-v2020.2
+```
+
+Make the necessary modifications and commit the changes.
+
+```
+$ git add *
+$ git commit -m "Doing something."
+```
+
+Produce the new patch.
+
+```
+$ git diff -p xilinx-v2020.2 HEAD > my-u-boot.patch
+```
+
+Solution in case of problems with whitespaces.
+
+```
+$ emacs u-boot-scalp-sja1105.patch -f delete-trailing-whitespace -f save-buffer -f kill-emacs
+```
+
+Apply the new patch to a clean version of the U-Boot GIT deposit.
+
+```
+$ git clone https://github.com/Xilinx/u-boot-xlnx.git
+$ cd u-boot-xlnx
+$ git checkout xilinx-v2020.2
+$ git apply u-boot-scalp-sja1105.patch
+```
+
+And that's it.