CONFIG_GPTMR0_CLOCKSOURCE is not available for thedefaultarchitecture x86.
Result is shown for architecture blackfin

Use GPTimer0 as a clocksource

configname: CONFIG_GPTMR0_CLOCKSOURCE

Blackfin Kernel Configuration
└─>Blackfin Processor Options
└─>Board customizations
└─>Use GPTimer0 as a clocksource
In linux kernel since version 2.6.31 (release Date: 2009-09-09)