[PATCH v2] serial: ns16550: Move PCI access from ofdata_to_platdata() to probe()

[Bin Meng]

On Mon, Mar 2, 2020 at 9:41 PM Wolfgang Wallner
<wolfgang.wallner at br-automation.com> wrote:
>
> Currently the ofdata_to_platdata() method calls dev_read_addr_pci(),
> which potentially accesses the parent PCI bus. If this happens before
> the parent PCI bus is probed the resulting address will be wrong.
>
> This behavior was triggered by commit 82de42fa1468 ("dm: core:
> Allocate parent data separate from probing parent").
>
> According to a comment in drivers/pci/pci-uclass.c [1] accessing
> the PCI parent bus in ofdata_to_platdata() is not allowed, and the
> access should be moved to the probe() function.
>
> Move the call to dev_read_addr_pci() and the related handling of the
> 'addr' value from the ofdata_to_platdata() to its own function,
> which is then called from the probe() method.
>
> While moving the code, the comment /* try Processor Local Bus device
> first */ was dropped. It was initially added with commit 3db886a5bf38
> ("serial: ns16550: Support ns16550 compatible pci uart devices") and
> later made obsolete with commit 33c215af4b9d ("dm: pci: Add a function
> to read a PCI BAR").
>
> [1] Comment in drivers/pci/pci-uclass.c:
> "A common cause of this problem is that this function is called in the
> ofdata_to_platdata() method of @dev. Accessing the PCI bus in that
> method is not allowed, since it has not yet been probed. To fix this,
> move that access to the probe() method of @dev instead."
>
> Signed-off-by: Wolfgang Wallner <wolfgang.wallner at br-automation.com>
>
> Fixes: 82de42fa1468 ("dm: core: Allocate parent data separate from
> probing parent")
>
> ---
> The discussion leading to this patch is located at
> https://lists.denx.de/pipermail/u-boot/2020-February/399811.html
>
> I have moved the code from probe() to a new function called
> ns1655_serial_set_base_addr() to keep the probe() simple.
>
> Changes in v2:
>  - Fixed build guards
>  - Moved code from probe() to a new function called
>    ns1655_serial_set_base_addr() to keep the probe() simple
>  - Removed RFC tag
>
>  drivers/serial/ns16550.c | 40 ++++++++++++++++++++++++++++------------
>  1 file changed, 28 insertions(+), 12 deletions(-)
>

Reviewed-by: Bin Meng <bmeng.cn at gmail.com>
Tested-by: Bin Meng <bmeng.cn at gmail.com> # Tested on Intel Galileo