In India, when your employer files for temporary work permit as per the current processing time it would take around 12 weeks (3 months). During this process you would not require to submit any passport. Later when your work permit is approved, your employer or third party would forward you the work permit approval letter.
Now at this stage, the next process is to apply for Temporary resident Visa ( This is required to enter Canada each time)
So your employer now submits a new package to the Visa office (Work permit approval letter, upfront medicals, TRV application forms, passport, Canada visa photos and other supporting documents) Only during this stage you would be submitting your passport to the visa office. The current processing time for this TRV stage is 27 days from India.
Hence your passport would not be with the visa office not more than 4 weeks.
Please note: While coming to Canada, you need to carry the Work permit Approval letter issued earlier as the officer at the port of entry issues the original hard copy of the work permit on basis of this approval letter.