Hello.
It is highly likely that this is a hardware problem. If the phone had not been damaged in any way prior to the white screen, the belt allowing the screen to function correctly may now be faulty (These things happen by themselves over time) and may need replacement. For this main reason, I do not believe it is software related.
Should the problem persist after having your LCD (screen) replaced with a properly functional new one, there may be another cause.
It is highly likely that this is a hardware problem. If the phone had not been damaged in any way prior to the white screen, the belt allowing the screen to function correctly may now be faulty (These things happen by themselves over time) and may need replacement. For this main reason, I do not believe it is software related.
Should the problem persist after having your LCD (screen) replaced with a properly functional new one, there may be another cause.