Dugger, Donald D
2008-Oct-16 19:42 UTC
[Xen-devel] [PATCH] Enable PCI serial devices for console messages
The basic issue is that some PCI serial devices use a non-standard crystal to
control the baud rate divisor. This patch enhances the `com'' parameter
to enable you to specify the crystal frequency used by the serial device. Since
this parameter already allows you to specify I/O address and IRQ this is all
that is needed to get a PCI serial device to work. With this patch the
`com'' parameter is now defined as:
comN=BBB,NPS,III/CCC,IRQ
Where `N'' is the com port number (1 or 2), `BBB'' is the baud
rate, `NPS'' is the number of bits per character, parity and number of
stop bits (defaults to 8n1), III is the I/O port address (defaults to 0x3f8 for
`com1'' and 0x2f8 for `com2''), `CCC'' is the crystal
frequency (typically the highest baud rate supported by the UART, defaults to
115200) and `IRQ'' is the interrupt number (defaults to 4 for
`com1'' and 3 for `com2''). Note that if you specify 0 for
`IRQ'' Xen will run the serial device in polled mode, obviating the need
for interrupts (an advantage since this is the only way I was able to get my PCI
serial device to work).
As an example, I am using the xen boot command:
kernel /xen.gz com1=115200,8n1,0xe880/921600,0 console=com1
Signed-off-by: Don Dugger <donald.d.dugger@intel.com>
--
Don Dugger
"Censeo Toto nos in Kansa esse decisse." - D. Gale
Donald.D.Dugger@intel.com`
Ph: (303)443-3786
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