Here's my system.xml field definition:
<fields>
<upload translate="label">
<label>Upload Latest</label>
<comment><![CDATA[This file gives you a more up-to-date BIN database. Please upload one regularly to stay ahead.]]></comment>
<frontend_type>file</frontend_type>
<backend_model>adminhtml/system_config_backend_file</backend_model>
<upload_dir>var/uploads</upload_dir>
<sort_order>50</sort_order>
<show_in_default>1</show_in_default>
<show_in_website>0</show_in_website>
<show_in_store>0</show_in_store>
</upload>
</fields>
The field shows successfully, but for some reason, when I browse for a file and click Save Config, it just redirects me to the Dashboard, there's no communication with any models, it literally just loads the dashboard.
How can I debug this issue successfully?
Update
After some additional digging, it appears to accept some files.
The particular file I'm looking to upload is a CSV that is 11.9 Mb. I've tried a small Jpg and it uploads successfully.
Could be to do with Filesize or File Type. How do I specifically enable CSV and increase the File Size limit to 20Mb?