Re: [PATCH] V4 pci uart - better cope with UART being temporarily unavailable

[Keir Fraser <keir.xen@gmail.com>]

On 27/08/2013 15:05, "Tomasz Wroblewski" <tomasz.wroblewski@citrix.com>
wrote:

> This happens for example when dom0 disables ioport responses during PCI
> subsystem initialisation. If a __ns16550_poll() happens to be scheduled during
> that time, Xen hangs. Detect and exit that condition.
> 
> Amended ns16550_ioport_invalid function to only check IER register, which
> contins 3 reserved (always 0) bits, therefore it's sufficient for that test.
> 
> Changes since V3:
> * readded invalid port test in the loop in __ns16550, moved it before
> serial_rx_interrupt call
> 
> Changes since V2:
> * pulled out invalid port test before the loop in __ns16550_poll
> * coding style/patch size fixes
> 
> Changes since V1:
> * added invalid port test in getc()
> * changed ns16550_tx_ready to return -EIO and code in serial.[ch] to cope with
> that error condition. If port is temporarily unavailable tx_ready will return
> -EIO and serial driver code will attempt to buffer the character instead of
> dropping it.
> 
> Signed-off-by: Tomasz Wroblewski <tomasz.wroblewski@citrix.com>
> ---

Acked-by: Keir Fraser <keir@xen.org>