Shortly after it was the rollout for the Xiaomi Mi Note, the Marshmall update has also started seeding to the company's Mi 4 flagship smartphone. As you can see in the screenshot above, the device is directly being updated to Android Marshmallow version 6.0.1, compared to the Mi Note which is supposed to get Android 6.0. The update, which bumps the build number to MMB29M, reportedly weighs in at around 100 MB. In case you aren't already aware, the phone was launched back in 2014 running Android 4.4.3 (KitKat) out-of-the-box. It received Android 5.1.1-based MIUI 7 update last October and the MIUI 7.1 update this month. A Xiaomi executive confirmed last month that the device, along with the Mi Note, will get the Marshmallow update...
Source: http://www.gsmarena.com/xiaomi_mi_4_starts_getting_android_601_marshmallow_update-news-16225.php