[coreboot-gerrit] Change in em100[master]: Update the README with a bit more detail

[Martin Roth (Code Review)]

Martin Roth has uploaded this change for review. ( https://review.coreboot.org/c/em100/+/34831 )

Change subject: Update the README with a bit more detail
......................................................................

Update the README with a bit more detail

This is not very helpful at present. Update it to describe the tool in
general terms.

BUG=chromium:918574
TEST=none

Change-Id: I044294d3fb98b94c8c02d6beb27676c96cc3a953
Signed-off-by: Simon Glass 
---
M README
1 file changed, 28 insertions(+), 3 deletions(-)

git pull ssh://review.coreboot.org:29418/em100 refs/changes/31/34831/1

diff --git a/README b/README
index 9ad4c14..7a76794 100644
--- a/README
+++ b/README
@@ -1,11 +1,33 @@
-em100: EM100pro command line utility
+em100: EM100-Pro command-line utility
+
+This tool supports using the Dediprog EM100-Pro [1] in Linux. It supports both
+the original version and the new -G2 variant.
+
+The 'em100' device provides a way to emulate a SPI-flash chip. Various
+connectors are available to allow it to take over from the in-circuit SPI chip
+so that the SoC sees the em100's internal memory as the contents of the SPI
+flash. Images can be loaded into the em100 over USB in a few seconds, thus
+providing a much faster development cycle than is possible by reprogramming
+the SPI flash each time.

Example:
-  ./em100 --stop --set M25P80 -d file.bin -v --start -t -O 0xfff00000
+  ./em100 --stop --set M25P80 -d file.bin --start -t -O 0xfff00000
+
+Major features provided by the tool include:
+
+- Set the chip being emulated (the tool supports about 600)
+- Adjust the state of the hold pin, which supports overriding the internal SPI
+- Use of several em100 devices, distinguished by their serial number
+- Terminal mode, allowing the SoC to send messages
+- Output a trace of SPI commands issued by the SoC
+- Reading / writing em100 firmware (dangerous as it can brick your em100)
+
+For help, use the -h option:

Usage:
   -c|--set CHIP:                  select chip emulation
-  -d|--download FILE:             upload FILE into EM100pro
+  -d|--download FILE:             download FILE into EM100pro
+  -u|--upload FILE:               upload from EM100pro into FILE
   -r|--start:                     em100 shall run
   -s|--stop:                      em100 shall stop
   -v|--verify:                    verify EM100 content matches the file
@@ -23,3 +45,6 @@
   -D|--debug:                     print debug information.
   -h|--help:                      this help text

+
+[1] https://www.dediprog.com/product/EM100Pro-G2
+