Whenever I need to quickly test the flash hardware (thus excluding sw driver and application), I usually stick with the raw method:
I directly access the flash base address with IOWR/IORD and I use the flash command interface. Refer to the actual flash meory datasheet: you usually need only 3 IOWRs to enter auto-select mode and then get device information with IORD.
This way you immediately test if the flash is 'alive'. Afterwards you can perform more exhaustive tests.
