Re: [PATCH v3 2/2] arm64: dts: Add BRCM IPROC NAND DT node for NS2

From: Ray Jui
Date: Fri Oct 30 2015 - 14:55:51 EST

On 10/30/2015 11:49 AM, Brian Norris wrote:
On Wed, Oct 28, 2015 at 09:08:02AM -0700, Ray Jui wrote:
On 10/28/2015 2:06 AM, Anup Patel wrote:

I think for a newly created OF devices the Linux device driver framework will
match the platform drivers in the order in which they are registered by module
init functions. Now the order of module init function calls will be based how
the .initcall section is formed by linker and order in which objects are linked.

Yes, what you said is my understanding as well, but then here is the
mystery. This is the link order in brcmnand/Makefile:

1 # link order matters; don't link the more generic brcmstb_nand.o
before the
2 # more specific iproc_nand.o, for instance
3 obj-$(CONFIG_MTD_NAND_BRCMNAND) += iproc_nand.o
4 obj-$(CONFIG_MTD_NAND_BRCMNAND) += bcm63138_nand.o
5 obj-$(CONFIG_MTD_NAND_BRCMNAND) += brcmstb_nand.o
6 obj-$(CONFIG_MTD_NAND_BRCMNAND) += brcmnand.o

Based on the order above, probe from iproc_nand should always be
called first if a matching compatible string is found. If so, then
why having both compatible strings "brcm,brcmnand" and
"brcm,nand-iproc" causes issues for NS2 (I remember it broke
smoketest in the past when you submitted the change)? I'm not saying
we should have "brcm,brcmnand" for iProc devices, but I don't get
why it would cause any issue.

FWIW, the above hack doesn't do anything if these are built as modules,
AFAICT. So I guess udev's (or similar) module rules would be another
point of failure here? Not that any of us probably care too much about
this driver as a module, but just throwing it out there...

I have a feeling we'll have to solve this locally, by avoiding having
"independent" drivers handling similar compatible properties, as I
expect (despite our expectation that compatible ordering should matter)
this problem will not be solved any time soon in the generic

Or we can just use a hack (as Anup is doing) to leave off the
"brcm,brcmnand" compatibility property. Unless someone has brilliant
ideas, I guess we go with Anup's hack for now.

I'm fine with that, :)



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