From 3635e2fabcc9928d6a89bfef2fe28d4c7d28824c Mon Sep 17 00:00:00 2001
From: David Cermak <cermak@espressif.com>
Date: Wed, 21 Jun 2023 10:36:29 +0200
Subject: [PATCH] docs(modem): Add known issues section to docs

Also updates self-hosted runner tag (from runner name to test scope
related tag)
---
 .github/workflows/modem__target-test.yml |  2 +-
 docs/esp_modem/en/README.rst             | 40 ++++++++++++++++++++++++
 2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/modem__target-test.yml b/.github/workflows/modem__target-test.yml
index 5a775c346..02d6ed0e4 100644
--- a/.github/workflows/modem__target-test.yml
+++ b/.github/workflows/modem__target-test.yml
@@ -58,7 +58,7 @@ jobs:
     needs: build_esp_modem_tests
     runs-on:
       - self-hosted
-      - BrnoRPI-GH006
+      - modem
     env:
       TEST_DIR: components/esp_modem/${{ matrix.test.path }}
     steps:
diff --git a/docs/esp_modem/en/README.rst b/docs/esp_modem/en/README.rst
index 1cc8a18ab..e87ad5a27 100644
--- a/docs/esp_modem/en/README.rst
+++ b/docs/esp_modem/en/README.rst
@@ -130,3 +130,43 @@ Is defined using standard configuration structures for ``DTE`` and
 
 - :cpp:class:``esp_modem_dte_config_t``
 - :cpp:class:``esp_modem_dce_config_t``
+
+Known issues
+------------
+
+There are certain issues, especially in using CMUX mode which you can
+experience with some devices:
+
+1) Some modems (e.g. A76xx serries) use 2 bytes CMUX payload, which
+might cause buffer overflow when trying to defragment the payload.
+It's recommended to disable ``ESP_MODEM_CMUX_DEFRAGMENT_PAYLOAD``,
+which will fix the issue, but may occasional cause reception of AT command
+replies in fragments.
+
+2) Some devices (such as SIM7000) do not support CMUX mode at all.
+
+3) Device A7670 does no not correctly exit CMUX mode. You can apply
+this patch to adapt the exit sequence https://github.com/espressif/esp-protocols/commit/28de34571012d36f2e87708955dcd435ee5eab70
+
+::
+
+      diff --git a/components/esp_modem/src/esp_modem_cmux.cpp b/components/esp_modem/src/esp_modem_cmux.cpp
+      index 0c480f8..4418c3d 100644
+      --- a/components/esp_modem/src/esp_modem_cmux.cpp
+      +++ b/components/esp_modem/src/esp_modem_cmux.cpp
+      @@ -206,6 +206,15 @@ bool CMux::on_header(CMuxFrame &frame)
+      }
+      size_t payload_offset = std::min(frame.len, 4 - frame_header_offset);
+      memcpy(frame_header + frame_header_offset, frame.ptr, payload_offset);
+      +    if (frame_header[1] == 0xEF) {
+      +        dlci = 0;
+      +        type = frame_header[1];
+      +        payload_len = 0;
+      +        data_available(&frame.ptr[0], payload_len); // Notify DISC
+      +        frame.advance(payload_offset);
+      +        state = cmux_state::FOOTER;
+      +        return true;
+      +    }
+      if ((frame_header[3] & 1) == 0) {
+            if (frame_header_offset + frame.len <= 4) {
+                  frame_header_offset += frame.len;