1. The construction pistis followed by a genitive of person or of a personal pronoun occurs in Paul's writings 24 times. All of them refer to the faith of the individual, never faith in the individual.
a. 20 times of individual Christians.
b. Once of God himself, Rom. 3.3
c. Twice of Abraham, Rom. 4.12, 16.
d. Once to anyone who has faith reckoned as righteousness, Rom. 4.5
2. A change of idiom occurs in Gal. 2.16.
There is the change from pistis christou with episteusamen Christon Iesoun.
3. The Syria Peshitta understands it as a subjective.
a. Gal. 2.16: "Therefore we know that a man is not justified from works of the law, but by the faith of Jesus the Messiah, and we believe in him, in Jesus the Messiah, that from his faith, that of the Messiah, we might be justified, and not from the works of the law."
b. Eph. 3.12:"In him we have the boldness and teh access in teh confidense of his faith".
4. Luther was the first exegete to translate the construction as "faith in". [Note, this is patternly false!]
In sum, I think it highly probable that Eph. 3.12 is a subjective genitive since the definite article + the genitive normally indicates a subjective genitive. The thought also comports closely with Hebrews 3.6 which espouses a similar idea. I think it most probable that Phil. 3.9 is a subjective gentivie due to the parrallelism of the verses and the preceding context of Phil. 2.5-11 which emphasizes the obedience of Christ. I translate Phil. 3.7-9 as follows:
For his sake I have suffered the loss of all things, and I regard them as human filth, in order that I may gain Messiah and be found in him, not having a righteousness of my own that comes from the Law, but one that comes through the faithfulness of the Messiah, the righteousness from God based upon faith.
I don't think the references in Galatians and Romans are subjective genitives since Paul is simply being emphatic (not redundant) in Rom. 3.22 about justification being by faith. Perhaps the most compelling piece of evidence against a widespread reading of the subjective genitive is that the Greek-speaking early church Fathers like Chrysostom did not interpret them as subjective genitives!
The best summary of the debate I have read comes from Tonstad, Sigve. 2002. ‘pistis christou: Reading Paul in a New Paradigm.’ AUSS 40: 37-59.
A good refutation of the subjective genitive interpretation can be found in the Pauline Theologies of either James Dunn or Thomas Schreiner.