Meek Mill, who spent time in prison and on probation after he was convicted on drug and gun charges in 2008, will face no other penalties as part of his plea agreement with prosecutors, the Philadelphia Inquirer reported, citing a court hearing.

"I'm extremely grateful that my long legal battle is finally behind me and I appreciate that it has sparked a much-needed discussion about probation reform and the inequalities that exist within our two Americas," Meek Mill said on Twitter on Tuesday.

Meek Mill, an African-American born Robert Rihmeek Williams, became a cause celebre for musicians, celebrities and criminal justice reform campaigners who said his case was typical of a US legal system that treats minorities unjustly.

He had already served about two years in prison over the 2007 case, and a judge decided he would not spend any additional time behind bars.

A Pennsylvania appeals court ruled last month that Mill was entitled to a new trial after it found that Philadelphia Judge Genece Brinkley, who presided over a 2008 trial that resulted in his conviction, was no longer impartial.

In November 2017, Brinkley sentenced the rapper to up to four years in prison, saying a pair of arrests violated probation conditions she set following his 2008 convictions. He served five months before the state's top court granted him bail. Neither of the arrests resulted in convictions.

The sole witness against Meek Mill at his 2008 trial was a discredited Philadelphia narcotics squad officer who is no longer with the city's police force.

Williams has called the 12-year ordeal "mentally and emotionally challenging" but says millions of people face the same issues.

He has helped start a foundation to promote criminal justice reform.

Australian Associated Press