In Paul’s undisputed writings, various phrases referring to faith of Jesus Christ appear seven times. While a literal translation for these phrases (pistis + genitive) using the words "faith of" is found in the King James Version, English translations common since the Protestant Reformation tend to translate these passages using the phrase "faith in" (Bassler 28). For many, rallied by Luther’s doctrine of sola fide, there is little difference between "faith of Christ" and "faith in Christ." But for a growing body of scholars the question of whether "faith of Christ" can justifiably be translated as "Christ’s faith" (a subjective genitive) has become a heated debate (Bassler 27). For several reasons it appears that rendering these passages as referring to Christ’s own faith may be an acceptable interpretation. 
First, Bassler points out that the general use of pistis followed by a personal noun or pronoun in the genitive in the writings of Hellenistic Judaism is almost exclusively a subjective genitive (29). Further, beyond the seven instances of pistis + genitive that refer to Christ, an additional 24 occurrences can be found in the same writings with different referents, all of which use the subjective genitive (Bassler 29). And more specifically, the Romans passages that reference the "faith of Jesus (Christ)" (3:22, 26) are embedded in passages with parallel constructions that use the genitive subjective construction to refer to the faithfulness of God (3:3) and the faith of Abraham (4:12, 16), providing contextual markers that point to a genitive subjective form to be used for the faith of Jesus as well (Bassler 29).  In the light of the Hellenistic Judaism tradition, Paul’s own usage of pistis + genitive constructions that refer to the faith of others, and the enclosing genitive subjective markers used in Romans, I would choose to translate these passages as "faith of Christ" rather than "faith in Christ."
It appears that this issue was also troubling to the early churches within the Pauline tradition as the authors of the deutero-Pauline letters primarily avoided the ambiguous pistis + genitive construction, opting for more explicit references to "faith in Christ."  One might speculate that the free gift of God through the faith of Jesus was simply too much to bear. Though Paul’s letters went to great lengths to break down boundary markers between the Jewish and Gentile groups, within a generation it would appear that new boundary markers, separating those with faith from those without, were erected by these early communities. This would not be the end of theologically based arguments. As Bassler points out, the most common supporting reasons for the "faith in Christ" translation are based on theological positions rather than linguistic evidence. Proponents of the "faith in Christ" view suggest:
a) that the reading "faith of Christ" stands against Reformation teaching of sola fide;
b) that faith is not appropriate for the Son of God, who should instead be the object of faith; and
c) that Paul has created a logical argument contrasting human works and human faith (Bassler 30).
Raised within the Southern Baptist Convention I understand the arguments of salvation by faith alone and the rejection of works-based righteousness. However, from a linguistic point of view, it is difficult to dismiss the evidence pointing toward a "faith of Christ" translation.
Theological counterpoint may also be offered to the "faith in Christ" arguments. Though troubling to the Protestant theological framework, there have been strong themes of Christian universalism throughout the history of the Church that point to Jesus as Christus Victor who frees all the world from the power of sin and death. Within Romans, Paul himself makes an argument suggesting that through the sin of one man (Adam) all humanity was condemned, while through the righteous act of one man (Jesus) all people (Greek pantes anthropoi) are justified and receive life (Romans 5:18). Further, as Bassler points out there is a strong mystical metaphor that runs through Paul’s writings as he speaks of being "in Christ" (31). It is exactly within this context that the "faith of Christ" passages occur in Galatians. First Paul claims that humanity (anthropos) is justified not through works of the law, but through the "faith of Christ" (Galatians 2:16) and then follows up on this assertion with the mystical image that, having been crucified with Christ, it is no longer he (Paul) that lives, but Christ who lives in him (Galatians 3:20). In this same verse Paul again asserts that he now lives his life by the "faith of the Son of God," which he appears to share in through the mystical indwelling that he has described.
Of course, there are several models of salvation found within Paul’s writings and no one model can clearly be singled out as Paul’s primary model for salvation. With this in mind it appears that the "faith of Christ" motif is one more theme in Paul’s overall narrative of the Good News as he shares with his various audiences.
 These include "faith of Jesus" (Romans 3:26), "faith of Christ" (Galatians 2:16; Philippians 3:9), "faith of Jesus Christ" (Romans 3:22; Galatians 2:16, 3:22), and "faith of the son of God" (Galatians 2:20).
 The exception being Ephesians 3:12, which uses the ambiguous genitive construction.
 Erhman points out mediation by Christ, ransom paid for captives, sacrificial atonement and rescue from physical danger (367).
Bassler, Jouette M. Navigating Paul: an introduction to key theological concepts. Louisville: Westminster John Knox, 2007.
Ehrman, Bart D. The New Testament: a historical introduction to the early Christian writings. 4th Edition. New York: Oxford University Press, 2008.