Re: [Xen-devel] [PATCH v2 1/7] serial: Skip over PCIe device which have no quirks (fix AMT regression).

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 07.03.14 at 20:01, Konrad Rzeszutek Wilk <konrad@xxxxxxxxxx> wrote:
> The "ns16550: Add support for UART present in Broadcom TruManage
> capable NetXtreme chips" implies that only devices that are have
> an MMIO BAR and are in the quirks table should be processed.
> 
> Even the comment at the end says so:
> 
>  If we have an io_base, then we succeeded in the lookup
> 
> But the code was checking for the !io_base - which is to say if
> the io_base was 0 then we would skip scanning. But io_base
> always has a value - it is set by 'ns16550_init' to a default
> value - so it would never hit the 'continue' path.
> 
> This means that if we have an communication device followed by
> a serial AMT device we would pick the communication device instead
> of the AMT device.
> 
> See:
> 00:16.0 Communication controller: Intel Corporation Cougar Point HECI 
> Controller #1 (rev 04)
>         Subsystem: Intel Corporation Device 2008
>         Flags: bus master, fast devsel, latency 0, IRQ 11
>         Memory at fb12a000 (64-bit, non-prefetchable) [size=16]
> 00:16.3 Serial controller: Intel Corporation Cougar Point KT Controller (rev 
> 04) (prog-if 02 [16550])
>         Subsystem: Intel Corporation Device 2008
>         Flags: bus master, 66MHz, fast devsel, latency 0, IRQ 17
>         I/O ports at f0e0 [size=8]
>         Memory at fb129000 (32-bit, non-prefetchable) [size=4K]
> 
> pci 0000:00:16.0: [8086:1c3a] type 00 class 0x078000
> pci 0000:00:16.3: [8086:1c3d] type 00 class 0x070002
> 
> And Xen picks 00:16.0 as its console when using 'com1=115200,8n1,amt'.
> 
> This patch fixes it and allows us to use AMT again by zeroing
> out io_base to zero. If the scan did not work, the io_base is
> set back to a default value (the 'pci_uart_config' does that
> already at its end).
> 
> CC: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@xxxxxxx>
> CC: Suravee Suthikulpanit <Suravee.Suthikulpanit@xxxxxxx>
> CC: Thomas Lendacky <Thomas.Lendacky@xxxxxxx>
> CC: Jan Beulich <jbeulich@xxxxxxxx>
> CC: Keir Fraser <keir@xxxxxxx>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

> ---
>  xen/drivers/char/ns16550.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c
> index 53e49a1..2fded08 100644
> --- a/xen/drivers/char/ns16550.c
> +++ b/xen/drivers/char/ns16550.c
> @@ -616,6 +616,7 @@ pci_uart_config (struct ns16550 *uart, int skip_amt, int 
> bar_idx)
>      unsigned int b, d, f, nextf, i;
>      u16 vendor, device;
>  
> +    uart->io_base = 0;
>      /* NB. Start at bus 1 to avoid AMT: a plug-in card cannot be on bus 0. */
>      for ( b = skip_amt ? 1 : 0; b < 0x100; b++ )
>      {
> -- 
> 1.7.7.6




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