Re: [RFC][PATCH] axi: add AXI bus driver

[RafaÅ MiÅecki]

2011/4/12 George Kashperko <george@xxxxxxxxxxx>:
>
>> Hi,
>>
>> On Tue, Apr 12, 2011 at 01:57:07AM +0200, RafaÅ MiÅecki wrote:
>> > Cc: Michael BÃsch <mb@xxxxxxxxx>
>> > Cc: Larry Finger <Larry.Finger@xxxxxxxxxxxx>
>> > Cc: George Kashperko <george@xxxxxxxxxxx>
>> > Cc: Arend van Spriel <arend@xxxxxxxxxxxx>
>> > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
>> > Cc: Russell King <rmk@xxxxxxxxxxxxxxxx>
>> > Cc: Arnd Bergmann <arnd@xxxxxxxx>
>> > Cc: Andy Botting <andy@xxxxxxxxxxxxxxx>
>> > Cc: linuxdriverproject <devel@xxxxxxxxxxxxxxxxxxxxxx>
>> > Cc: linux-kernel@xxxxxxxxxxxxxxx <linux-kernel@xxxxxxxxxxxxxxx>
>> > Signed-off-by: RafaÅ MiÅecki <zajec5@xxxxxxxxx>
>> > ---
>> > V2: Rename to axi
>> > Â Â Use DEFINE_PCI_DEVICE_TABLE in bridge
>> > Â Â Make use of pr_fmt and pr_*
>> > Â Â Store core class
>> > Â Â Rename bridge to not b43 specific
>> > Â Â Replace magic 0x1000 with BCMAI_CORE_SIZE
>> > Â Â Remove some old "ssb" names and defines
>> > Â Â Move BCMAI_ADDR_BASE def
>> > Â Â Add drvdata field
>> > V3: Fix reloading (kfree issue)
>> > Â Â Add 14e4:0x4331
>> > Â Â Fix non-initialized struct issue
>> > Â Â Drop useless inline functions wrappers for pci core drv
>> > Â Â Proper pr_* usage
>> > V3.1: Include forgotten changes (pr_* and include related)
>> > Â Â Explain why we dare to implement empty release function
>>
>> I'm not sure we need this. If you have an IP Core which talks AXI and
>> you want to put it on a PCI bus, you will have a PCI Bus wrapper around
>> that IP Core, so you should go and let the kernel know about that. See
>> [1] for a core IP which talks AXI and [2] for a PCI bus glue layer.
>>
>> Besides, if you introduce this bus layer, it'll be more difficult for
>> other licensees of the same core to re-use the same driver, since it's
>> now talking a PCI emulated on top of AXI. The same can be achieved with
>> the platform_bus which is more widely used, specially on ARM SoCs.
>>
>> [1] http://gitorious.org/usb/usb/blobs/dwc3/drivers/usb/dwc3/core.c
>> [2] http://gitorious.org/usb/usb/blobs/dwc3/drivers/usb/dwc3/dwc3-haps.c
>>
>
> Already noticed earlier that AXI isnt really good name for
> Broadcom-specific axi bus customization. As of tech docs available from
> arm, corelink AXI cores use own identification registers which feature
> different format and layout comparing to that we use for Broadcom cores.
>
> Maybe there is something "standartized" by the DMP specs? If so I'm
> curious if that DMP is obligatory for every axi bus ?
>
> Naming particular Broadcom's implementation just axi limits other
> licensees in reusing axi bus name/code or will require hacks/workarounds
> from them to fit Broadcom-like core scanning/identificating techniques.
> You use bus named AXI to group and manage Broadcom cores, while never
> even publish device records for native axi cores Broadcom use to talk to
> the interconnect through. Yet again, something like bcmb/bcmai looks
> like better name for this bus.

I don't know, I'm really tired of this. Earlier I was told to not use
anything like bcmai, because it is not Broadcom specific. Now it seems
(and I'm afraid I agree) there is quite a lot of Broadcom specific
stuff.


> Also can't figure out how is this implementation supposed to manage
> multicore devices.

We have got ideas, but let's first find (wait for) such a device ;)


> Any plans on embeddables' support ?

Sure, if noone will come before me, I'll try to provide support for
embedded devices. However basic support for PCI host in higher on my
priority list. First I want to know it is working at all ;)

-- 
RafaÅ
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