Drivers currently cannot implement explicit cache handling and rely on
running the same code before and after mmu_initcall() without crashing.
Depending on the chosen config options, the cache functions are not yet
setup and using them early on ends in a null pointer dereference.
The RPi's mailbox driver is such a case; it requires cache handling once
the MMU is fully set up and yet the RPi setup needs to use the driver to
get the memory size before mem_initcall() and hence mmu_initcall().
Fix this by checking the cache_fns pointer before dereferencing it.
Signed-off-by: Andre Heider <a.heider@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
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