1 files changed, 131 insertions, 0 deletions
diff --git a/meta-openbmc-mods/meta-common/recipes-phosphor/configuration/entity-manager/0005-Allow-MUX-idle-state-to-be-configured-as-DISCONNECT.patch b/meta-openbmc-mods/meta-common/recipes-phosphor/configuration/entity-manager/0005-Allow-MUX-idle-state-to-be-configured-as-DISCONNECT.patch
new file mode 100644
index 000000000..ac0995614
--- /dev/null
+++ b/meta-openbmc-mods/meta-common/recipes-phosphor/configuration/entity-manager/0005-Allow-MUX-idle-state-to-be-configured-as-DISCONNECT.patch
@@ -0,0 +1,131 @@
+From aada39602a21e83d7e8c39c39fb8c5c32122863c Mon Sep 17 00:00:00 2001
+From: AKSHAY RAVEENDRAN K <akshay.raveendran.k@intel.com>
+Date: Thu, 2 Sep 2021 11:11:40 +0000
+Subject: [PATCH] Allow MUX idle state to be configured as DISCONNECT
+
+The existing Linux behavior is to leave the Mux status as it is after
+an operation. In HSBP and in other places we have more than one MUX
+parallel in same root bus. The existing behavior will result in reading
+multiple buses of different MUXes at the same time and causes bad read.
+In this fix, we can configure "MuxIdleMode" as "Disconnect" in
+configuration file as shown below
+
+{
+    "Address": "0x70",
+    "Bus": "$bus",
+    "ChannelNames": [
+        "Drive_1",
+        "Drive_2",
+        "Drive_3",
+        "Drive_4"
+        ],
+        "MuxIdleMode": "Disconnect",
+        "Name": "Drive Mux 1",
+        "Type": "PCA9546Mux"
+
+Tested:
+Set the MUX idle mode to Disconnect in MUXes present in HSBP board and
+only one channel is read at a time.
+
+Change-Id: I6d29cd3be350682c386bd3072e76b930a7d45587
+Signed-off-by: AKSHAY RAVEENDRAN K <akshay.raveendran.k@intel.com>
+---
+ src/Overlay.cpp | 55 ++++++++++++++++++++++++++++++++++++++++++++++---
+ 1 file changed, 52 insertions(+), 3 deletions(-)
+
+diff --git a/src/Overlay.cpp b/src/Overlay.cpp
+index 4454423..2843c31 100644
+--- a/src/Overlay.cpp
++++ b/src/Overlay.cpp
+@@ -38,11 +38,46 @@ constexpr const char* outputDir = "/tmp/overlays";
+ constexpr const char* templateChar = "$";
+ constexpr const char* i2CDevsDir = "/sys/bus/i2c/devices";
+ constexpr const char* muxSymlinkDir = "/dev/i2c-mux";
++constexpr const char* idleModeAsIs = "-1";
++constexpr const char* idleModeDisconnect = "-2";
+ 
+ constexpr const bool debug = false;
+ 
+ std::regex illegalNameRegex("[^A-Za-z0-9_]");
+ 
++void setIdleMode(const std::string& muxName, size_t busIndex, size_t address,
++                 const std::string& idleMode)
++{
++    std::error_code ec;
++
++    std::ostringstream hexAddress;
++    hexAddress << std::hex << std::setfill('0') << std::setw(4) << address;
++
++    std::filesystem::path idlePath(i2CDevsDir);
++    idlePath /=
++        std::to_string(busIndex) + "-" + hexAddress.str() + "/idle_state";
++
++    std::string modeData =
++        (idleMode == "Disconnect") ? idleModeDisconnect : idleModeAsIs;
++
++    if (debug)
++    {
++        std::cerr << "Setting " << muxName << " idle state to " << modeData
++                  << " in " << idlePath << "\n";
++    }
++
++    std::ofstream idleFile(idlePath);
++    if (!idleFile.good())
++    {
++        std::cerr << "Can't set idle mode in " << idlePath << " for " << muxName
++                  << "\n";
++    }
++    else
++    {
++        idleFile << modeData;
++    }
++}
++
+ // helper function to make json types into string
+ std::string jsonToString(const nlohmann::json& in)
+ {
+@@ -285,6 +320,7 @@ void exportDevice(const std::string& type,
+     std::shared_ptr<uint64_t> bus = nullptr;
+     std::shared_ptr<uint64_t> address = nullptr;
+     const nlohmann::json::array_t* channels = nullptr;
++    std::string idleMode;
+ 
+     for (auto keyPair = configuration.begin(); keyPair != configuration.end();
+          keyPair++)
+@@ -318,6 +354,11 @@ void exportDevice(const std::string& type,
+             channels =
+                 keyPair.value().get_ptr<const nlohmann::json::array_t*>();
+         }
++        else if (keyPair.key() == "MuxIdleMode")
++        {
++            idleMode = keyPair.value().get<std::string>();
++        }
++
+         boost::replace_all(parameters, templateChar + keyPair.key(),
+                            subsituteString);
+         boost::replace_all(devicePath, templateChar + keyPair.key(),
+@@ -327,10 +368,18 @@ void exportDevice(const std::string& type,
+     int err = buildDevice(devicePath, parameters, bus, address, constructor,
+                           destructor, createsHWMon);
+ 
+-    if (!err && boost::ends_with(type, "Mux") && bus && address && channels)
++    if (!err && boost::ends_with(type, "Mux") && bus && address)
+     {
+-        linkMux(name, static_cast<size_t>(*bus), static_cast<size_t>(*address),
+-                *channels);
++        if (channels)
++        {
++            linkMux(name, static_cast<size_t>(*bus),
++                    static_cast<size_t>(*address), *channels);
++        }
++        if (!idleMode.empty())
++        {
++            setIdleMode(name, static_cast<size_t>(*bus),
++                        static_cast<size_t>(*address), idleMode);
++        }
+     }
+ }
+ 
+-- 
+2.17.1
+