Re: [PATCH 6/7] dt-bindings: net: bgmac: add bindings documentation for bgmac

On Fri, Jul 1, 2016 at 5:46 AM, Arnd Bergmann [off-list ref] wrote:

On Thursday, June 30, 2016 6:59:13 PM CEST Jon Mason wrote:

quoted

+
+Required properties:
+ - compatible: "brcm,bgmac-nsp"
+ - reg:                Address and length of the GMAC registers,
+               Address and length of the GMAC IDM registers
+ - reg-names:  Names of the registers.  Must have both "gmac_base" and
+               "idm_base"
+ - interrupts: Interrupt number
+

"brcm,bgmac-nsp" sounds a bit too general. As I understand, this is a family
of SoCs that might not all have the exact same implementation of this
ethernet device, as we can see from the long lookup table in bgmac_probe().

The Broadcom iProc family of SoCs contains:
Northstar
Northstar Plus
Cygnus
Northstar 2
a few SoCs that are under development
and a number of ethernet switches (which might never be officially supported)

Each one of these SoCs could have a different revision of the gmac IP
block, but they should be uniform within each SoC (though there might
be a A0/B0 change necessary).  The Northstar Plus product family has a
number of different implementations, but the SoC is unchanged.  So, I
think this might be too specific, when we really need a general compat
string.

Broadcom has a history of sharing IP blocks amongst the different
divisions.  So, this driver might be used on other SoC families (as it
apparently has been done in the past, based on the code you
reference).  I do not know of any way to know what legacy, non-iProc
chips have used this IP block.  I can make this "brcm,iproc-bgmac",
and add "brcm,iproc-nsp-bgmac" as an alternative compatible string in
this file (which I believe you are suggesting), but there might be
non-iProc SoCs that use this driver.  Is this acceptable?

Thanks,
Jon

Please document the specific product numbers here that are publically
known already. Having the driver match just on "brcm,bgmac-nsp" as a fallback
is fine, so you can document that one as required for all users.

        Arnd

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