Re: [PATCH v2] ARM: CSR: Adding CSR SiRFprimaII board support

On Fri, Jul 01, 2011 at 08:04:06AM +0800, Barry Song wrote:

2011/6/30 Arnd Bergmann [off-list ref]:

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On Thursday 30 June 2011, Barry Song wrote:

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Is this really just one bus with a huge address space, or rather some
nested buses? I'd prefer to have the device tree representation as
close as possible to the actual layout.

there are two AXI buses in prima2. AXI-1 connect to memory, AXI-2 is
transferred to CSR self-defined IOBUS by CPUIF, then 1 intterupt
controller and 9 IO bridges are connected to the IOBUS .
The 9 IO bridges are SYSIOBG, PERIIOBG,CPURTCIOBG, UUSIOBG, GRAPHIOBG,
MEDIAIOBG, DSPIOBG, DISPIOBG, MEMIOBG. Every iobrg connect to a group
of controllers.
For example, DISPIOBG connect to VPP and LCD, SYSIOBG connect to CLKC,
RSTC, RSC and CPHIFBG, DSPIOBG connect to DSPIF, GPS and DSP.
PERIIOBG connect to TIMER, NAND, AUDIO, UART0, UART1, UART2, USP0,
USP1, USP2, SPI0, I2C0, I2C1, GPIO, *SYS2PCI* and so on. Then
*SYS2PCI* connect to SD.

The indendation descible the device hierarchy
AXI-1
         Memory
AXI-2
         interrupt controller
         IOBG...
                  xxxx
         IOBG...
                  xxxx
         IOBG...
                  xxxx
         IOBG...
                  xxxx
         IOBG...
                  xxxx
         IOBG...
                  SYS2PCI
                            SD

i have get the IC guy Weizeng involved, maybe he can explain better than me :-)

I think it would be good to represent the IOBG devices in the device tree then.
You don't need to represent AXI-1 because memory is special anyway, and I would
not bother to list SYS2PCI if the intention of that block was to hide the fact
that it's PCI behind it. Properly instantiating it as a PCI bridge would be
a lot of work that is probably not worth it.

My usual plea to hardware developers: Please make the registers
autodiscoverable from software! On an AMBA bus, please use the PrimeCell
register layout. If you always have an IOBG device behind, they should
all have the same identifier for that kind of bus bridge.

For the IOBG, it would be ideal to have a similar way of finding and
configuring the connected hardware, including:

* unique identifier for each distinct IP block
* revision of that block
* MMIO ranges and sizes, relative to the bus
* interrupt numbers, relative to a local interrupt controller
* location identifier (like PCI bus/device/fn number) that can be
 referred to by other devices
* clock management for that device
* power management for that device

If your IODB infrastructure already has this, you should create a new
bus-type for this in Linux, which will let you detect all devices
in a consistent manner without having to list them in the device tree.

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I think the namespace for the compatible values is supposed to start with
the stock ticker name of the company making the device as a unique
identifier. This means you'd have to use
"csrxf,sirf-intc", "csrxf,sirf-prima2-intc" as the value, instead
of starting with the product name. I don't know exactly how strictly
we apply that rule, but I've taken the devicetree-discuss-uLR06cmDAlatORQsKGg5Ig@public.gmane.orgbs.org
mailing list on Cc, maybe someone can clarify.

in fact, SiRF is a company name. it was merged into CSR 4 years ago.
Due to history reason, now the SoC names are still headed by sirf.
the logo in SiRFprimaII chip is CSR.
So the "SiRF" of SiRFprimaII should mean two things: old company name,
 heritable CPU production-line. Anyway, "csr, sirf-intc" seems to make
more senses than "sirf, intc".

could we change "csrxf,sirf-intc", "csrxf,sirf-prima2-intc" to
"csr,sirf-intc", "csr,sirf-prima2-intc"?

Not sure how strict we interpret the rules about stock ticker symbols.
'CSR' on wallstreet is 'China Security & Surveillance Tech. Inc'. If they
ever decide to produce embedded Linux machines, we'd get a conflict, unless
they also use "csst" (their .com domain name) as a prefix.

Hi Arnd,

ha-ha.

except Wall St and stock, i really didn't realize CSR is something
related with 'China Security & Surveillance Tech. Inc' . it seems CSR
is much more extensively known as a company in Wireless Technology,
Audio, Connectivity and GPS.
if we lost this name, people might not know it came from *that* CSR
focusing on Wireless/Audio/Connectivity/GPS. people will ask, what is
CSRXF? if we really use stock sticker symbols, CSR.L is the more
normal symbol in UK market. if we move to stock sticker symbol, could
we use CSR.L?

Fine by me.  Make sure it stays in uppercase when using the stock
ticker symbol.

g.