adding 16550 UART to RM9200

[Olivier Houchard]

Hi,

On Tue, Apr 03, 2007 at 05:48:58PM +0200, Bernd Walter wrote:
> I plan to add up to 48 16550 UART to an RM9200 system.
> It should be done with 16C554 chips - so I only have 16 byte FiFo.
> I would like to avoid using 64 byte FiFo chips, but those are pin
> compatible, so things are changeable in case.
> Likely most of the ports are doing low volume and I hope this will
> be Ok.
> They will be addressed via NCS2 space.
> Most of the external interrupts are not available because of
> unfortunate multiplexing with other required signals, so I have to
> attach them all to IRQ0.
> The interrupt will be level configured by firmware.
> And the NCS2 waitstates and buswidth will be configured by firmware
> as well.
> 
> However some question points are still left:
> 
> - How can I attach our uart(4) driver to the chips?
> It will likely addressed with:
> UART0	0x30000000 - 0x30000007 IRQ0
> UART1	0x30000008 - 0x3000000f IRQ0
> UART2	0x30000010 - 0x30000017 IRQ0
> UART3	0x30000018 - 0x3000001f IRQ0
> UART4	0x30000020 - 0x30000027 IRQ0
> UART5	0x30000028 - 0x3000002f IRQ0
> [...]
> UART47	0x30000170 - 0x30000177 IRQ0
> UART48	0x30000178 - 0x3000017f IRQ0
> 

I think you'll want to use hints.

> - I would like to use a 14,7456MHz xtal
> How can I tell uart(4) the frequency?
> 

You can play with the struct uart_devinfo.bas.rclk field.

> - How can I configure NCS2 range as being uncacheable?
> I asume this has to be done somehow in the kernel.
> 

pmap_mapdev() maps the physical range passed uncached, so you can use it.

Cheers,

Olivier