Re: [PATCH] serial: amba-pl011: do not request memory region twice

["Russell King (Oracle)" <linux@armlinux.org.uk>]

On Fri, Nov 26, 2021 at 03:39:25PM +0100, Lino Sanfilippo wrote:
> The driver attempts to request and release the IO memory region for a uart
> port twice:
> 
> First during the probe() function devm_ioremap_resource() is used to
> allocate and map the ports memory.
> Then a combo of pl011_config_port() and pl011_release_port() is used to
> request/release the same memory area. These functions are called by the
> serial core as soon as the uart is registered/unregistered.
> 
> However since the allocation request via devm_ioremap_resource() already
> succeeds, the attempt to claim the memory again via pl011_config_port()
> fails. This failure remains unnoticed, since the concerning return value is
> not evaluated.
> Later at module unload also the attempt to release the unclaimed memory
> in pl011_release_port() fails. This time the failure results in a “Trying
> to free nonexistent resource" warning printed by the serial core.
> 
> Fix these issues by removing the callbacks that implement the redundant
> memory allocation/release.

I think you will also need the verify_port method to also deny changing
port->mapbase.

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