GPMC in device tree

Ran Shalit ranshalit at gmail.com
Wed Aug 5 16:11:28 AEST 2015


On Wed, Aug 5, 2015 at 6:56 AM, Ran Shalit <ranshalit at gmail.com> wrote:
> On Wed, Aug 5, 2015 at 12:25 AM, Scott Wood <scottwood at freescale.com> wrote:
>> On Wed, 2015-08-05 at 00:22 +0300, Ran Shalit wrote:
>>> On Tue, Aug 4, 2015 at 11:31 PM, Scott Wood <scottwood at freescale.com> wrote:
>>> > On Tue, 2015-08-04 at 23:26 +0300, Ran Shalit wrote:
>>> > > On Tue, Aug 4, 2015 at 9:54 PM, Scott Wood <scottwood at freescale.com>
>>> > > wrote:
>>> > > > On Tue, 2015-08-04 at 18:29 +0300, Ran Shalit wrote:
>>> > > > > Hello,
>>> > > > >
>>> > > > > I would please like to ask if describing flash nor used with GPMC,
>>> > > > > whould be done as described in:
>>> > > > > https://www.kernel.org/doc/Documentation/devicetree/bindings/mtd/gpmc-nor.txt
>>> > > > > It is described in the above link as "TI's GPMC", so I'm not sure if
>>> > > > > it is relevent for powerpc too.
>>> > > >
>>> > > > That binding is for TI GPMC.
>>> > > >
>>> > > > Are you saying you have some PPC chip that has a flash controller
>>> > > > called
>>> > > > GPMC?
>>> > > >
>>> > > > -Scott
>>> > > >
>>> > >
>>> > > Hi Scott,
>>> > >
>>> > > Thanks, I've worked with TI's chips, so I now understand that I made
>>> > > here some confusion...
>>> > > It is GPCM , not GPMC, my mistake.
>>> > > We already configured it in u-boot, but on doing read/write from
>>> > > kernel it doesn not work.
>>> > > It seems that for the linux to use the correct driver, we need to
>>> > > define the nor in the device tree.
>>> > > Is there any example how to define nor GPCM in device tree ? Is it
>>> > > possible not to override the existing GPCM configuration ?
>>> >
>>> > Pretty much all of the mpc8xxx/qoriq device trees have GPCM NOR defined.
>>> > See
>>> > Documentation/devicetree/bindings/powerpc/fsl/lbc.txt and examples such as
>>> > arch/powerpc/boot/dts/p4080ds.dts (part of the lbc node is in
>>> > arch/powerpc/boot/dts/fsl/p4080si-post.dtsi).
>>> >
>>> > Linux will not change the GPCM configuration.
>>> >
>>> > -Scott
>>> >
>>>
>>> On more thing, if I may.
>>> The localbus is also connected to nvram & cpld.
>>> I've noticed that read/write works well, even though I didn't define
>>> anything in device tree.
>>> Is there any reasom to add these devices into device tree, or can we
>>> use the cpld and nvram without the definition in device tree ?
>>
>> I don't know what you're doing in your kernel to access devices that aren't
>> in the device tree.  You should add the devices to the device tree, and have
>> the kernel use it rather than hardcoded info.
>>
>> -Scott
>>
> Hi,
>
> Yes I understand.
> But It is worse noting that I have no localbus entry in the device tree.
> Yes, The nvram, cpld which are both connected to device tree, seems to
> work without any issues.
>
> Thanks,
> Ran

I apologyze for the bad english, I meant "it worth to note" that there
is no localbus entry at all in the device tree.
So I wander how the nvram and cpld worked...
If I may please ask, what should be the "compatible" for generic
devices such as  nvram/cpld ?
I assume that if they worked without any entry, it means that there is
no need for specific driver.

Regards,
Ran


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